Книга - Collins New Naturalist Library
Collins New Naturalist Library
L. Harrison Matthews
Mammals in the British Isles looks at the influences on their numbers and distribution, both now and in the past, examines aspects of their biology with emphasis on function and physiology, and concludes with an account of relationships with man.This book by Dr Harrison Matthews will be warmly welcomed by all those for whom his British Mammals, in this series, was a standard work for nearly 30 years. In recent years our understanding of the British species has expanded greatly. This volume offers a synthesis of modern knowledge derived from living animals studied in the field and covering all facets of mammalian life in the British Isles. It will be as important to a new generation of naturalists as the previous book was to an older one.The book is full of fascinating detail – of the shrews which scream in defence of territory to avoid fighting; of young rats that play to learn while adult otters play for fun; of vole 'plague' populations which crash as a result of stress; of monogamy and parental care of the dog fox – but it also paints a broader picture of interdependence, conservation and the part played by man.As much a part of nature as any other member of the fauna, it is man who has created the character of the environment – by clearing, draining, building and developing agriculture – and made available the wide variety of habitats occupied by indigenous, introduced and feral populations.Dr Harrison Matthews gives a general account of British mammals and the things influencing their numbers and distribution both now and in the past, examines aspects of their biology with emphasis on function and physiology, and concludes with an account of relationships with man and the measures he has taken for their control and conservation.
COPYRIGHT (#ulink_988af9f3-c520-5db0-b57e-454720bd2208)
William Collins
An imprint of HarperCollinsPublishers 1 London Bridge Street London SE1 9GF
WilliamCollinsBooks.com (http://WilliamCollinsBooks.com)
This eBook edition published by William Collins in 2019
First published 1982
Copyright © L. Harrison Matthews 1982
L. Harrison Matthews asserts his moral right to be identified as the author of this work.
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Adroit Photo-Litho Ltd, Birmingham
HarperCollinsPublishers has made every reasonable effort to ensure that any picture content and written content in this ebook has been included or removed in accordance with the contractual and technological constraints in operation at the time of publication.
Source ISBN 9780007417643
Ebook Edition © FEBRUARY 2019 ISBN: 9780007406562
Version: 2019–02–26
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[Page numbers taken from the following print edition: ISBN 9780007406562]
EDITORS
Margaret Davies, C.B.E., M.A., Ph.D.
Kenneth Mellanby, C.B.E., Sc.D.
S.M. Walters, M.A., Ph.D.
PHOTOGRAPHIC EDITOR
Eric Hosking, F.R.P.S.
The aim of this series is to interest the general reader in the wild life of Britain by recapturing the inquiring spirit of the old naturalists. The Editors believe that the natural pride of the British public in the native fauna and flora. to which must be added concern for their conservation, is best fostered by maintaining a high standard of accuracy combined with clarity of exposition in presenting the results of modern scientific research.
CONTENTS
COVER (#uc6b73b2f-0c45-5e7d-a041-ee60e42ba1f1)
TITLE PAGE (#u575e6921-cc68-5821-834d-eb7c97abc911)
COPYRIGHT (#ucd105388-b31e-5e92-a80d-f84cc108c15f)
Note to Readers (#u041acd61-5508-577a-96de-1a04dcdc3c8e)
PLATES (#u7c4f1209-f35e-50fd-bfc5-2f2d045c14b8)
EDITORS’ PREFACE (#ua7bf7cad-6516-5200-b3e3-efb712d399de)
AUTHOR’S PREFACE (#u6c6978ad-698e-5835-a9bd-f4eea2eefe85)
1. (#u92d9331a-a103-5bb2-94c7-f54a6c19a462)The Mammals of the British Isles (#u92d9331a-a103-5bb2-94c7-f54a6c19a462)
2. (#ub32c0dcb-1dc0-577c-ae8a-268e4047d9b3)Ice Ages (#ub32c0dcb-1dc0-577c-ae8a-268e4047d9b3)
3. (#uba1bb3a4-8610-500b-9805-0eb0fdf76132)The Evolution of the Environment (#uba1bb3a4-8610-500b-9805-0eb0fdf76132)
4. (#litres_trial_promo)Distribution and Habitats (#litres_trial_promo)
5. (#litres_trial_promo)Ranges, Territories and Populations (#litres_trial_promo)
6. (#litres_trial_promo)Social Behaviour (#litres_trial_promo)
7. (#litres_trial_promo)Behaviour and the Environment (#litres_trial_promo)
8. (#litres_trial_promo)Communication (#litres_trial_promo)
9. (#litres_trial_promo)Internal and External Rhythms (#litres_trial_promo)
10. (#litres_trial_promo)Man and the other Mammals (#litres_trial_promo)
PICTURE SECTION (#litres_trial_promo)
APPENDIX (#litres_trial_promo)
REFERENCES (#litres_trial_promo)
INDEX (#litres_trial_promo)
FOOTNOTES (#litres_trial_promo)
ABOUT THE PUBLISHER (#litres_trial_promo)
PLATES (#ulink_7a78a312-f645-599d-a3e4-a33450efc5ed)
1. (#litres_trial_promo)Hedgehog in nest; young hedgehog (G. Kinns) (#litres_trial_promo)
2. (#litres_trial_promo)Common shrew (G. Kinns), pygmy shrew (G. Kinns); lesser white-toothed shrew (D. Hosking) (#litres_trial_promo)
3. (#litres_trial_promo)Water shrew (G. Kinns); noctule bat (J.H.D. Hooper) (#litres_trial_promo)
4. (#litres_trial_promo)Roost of greater horseshoe bats in a cave (J.H.D. Hooper); the rare mouse-eared bat in flight (S.C. Bisserôt) (#litres_trial_promo)
5. (#litres_trial_promo)Water vole (D. Hosking); bank vole (G. Kinns); field vole’s nest (G. Kinns) (#litres_trial_promo)
6. (#litres_trial_promo)Yellow-necked mouse; wood mouse burrow; harvest mouse and summer nest (G. Kinns) (#litres_trial_promo)
7. (#litres_trial_promo)Common dormouse; edible or fat dormouse (G. Kinns) (#litres_trial_promo)
8. (#litres_trial_promo)Runway of common rat (G. Kinns); common rat feeding (G. Kinns); introduced coypu (L.M. Gosling) (#litres_trial_promo)
9. (#litres_trial_promo)Mountain hare (B. Tulloch); brown hare (G. Kinns) (#litres_trial_promo)
10. (#litres_trial_promo)Red squirrel (A.L. Goodson); grey squirrel in its den (F.W. Lane); litter of fir cones (G. Kinns) (#litres_trial_promo)
11. (#litres_trial_promo)Badger with old bedding; overlapping fox and badger territories (G. Kinns) (#litres_trial_promo)
12. (#litres_trial_promo)Country fox cubs (G. Kinns); town fox raiding a dustbin (D. Hosking) (#litres_trial_promo)
13. (#litres_trial_promo)A hunting weasel (G. Kinns); mink (F.W. Lane) (#litres_trial_promo)
14. (#litres_trial_promo)Tracks of an otter in snow (B. Tulloch); wild cat from the highlands of Scotland (G. Kinns) (#litres_trial_promo)
15. (#litres_trial_promo)Common seals on a sandbank in the Wash (R.W. Vaughan); grey seal (G. Kinns) (#litres_trial_promo)
16. (#litres_trial_promo)Two red stags; red deer-stag ‘roaring’; stag showing flehmen action (T. Clutton-Brock) (#litres_trial_promo)
EDITORS’ PREFACE (#ulink_d4b704f7-7034-5524-9e7a-07cbb29da5ea)
IT IS NOW over 30 years since Dr Matthews wrote his British Mammals, which was No. 21 in the New Naturalist series. The Editors then described it as ‘the most important book on British mammals that has ever been published, bringing together as it does an enormous number of facts into a new synthesis’. The reviewers and our public fully endorsed this opinion, and the book has been a continuing success ever since it was published. It is still the most useful volume in its field, and owners of copies will treasure them on their shelves, and make use of them in their studies, for many years to come.
British Mammals, when it was published, was topical and very up to date, bringing together the results of Dr Matthews’ own observations and the research of many other mammalogists. Since then the subject has made great progress, often stimulated by Dr Matthews’ own writings. As a result there was need for considerable addition to the original text, even though there was little that newer investigations had shown to require correction. British Mammals was already a long book, though every word of its text was interesting and worth reading. Further extensions and revisions would have produced a volume which, in today’s circumstances, would have been so expensive as to have been out of reach of many of those for whom it was intended – ‘the general reader interested in wildlife’.
It was for this reason that we persuaded Dr Matthews to produce an entirely new book. It is in no way a revision of the 1952 publication. Although considerably shorter than its predecessor, it covers all facets of the life of the mammals of the British Isles. Like others in this series, it is not a text book. Several admirable volumes of this nature are now available; this has made it possible to reduce the description of the species to a minimum. Once more the author has produced a synthesis of modern knowledge, which treats mammals as living creatures, living in and adapted to their environment. We are confident that it will meet a real need of today’s readers, and that it is a worthy successor to the author’s previous volume.
AUTHOR’S PREFACE (#ulink_2c98197e-c106-5973-a42e-08f7aefc67de)
THIRTY years have passed since my volume ‘British Mammals’ was published as No. 21 in the New Naturalist series, and a large amount of new information has come to hand during that time. The cost of resetting a fully revised new edition was too expensive for the publishers to face; I had therefore to insist that it should be allowed to go out of print – I could not let readers be fobbed off with so out-of-date a book. Paradoxically, the publishers then asked me to write a new and different book on our mammals, and here it is.
I have tried to give a general picture of the British mammals and the things influencing their numbers and distribution both now and in the past, together with the history and development of their environment. I then examine various aspects of their biology, dealing with them as living animals in the field rather than as captives in the laboratory or preserved specimens in museums. I have avoided elaborating technical points of anatomical structure unless they are relevant to matters of function and physiology. In a land so densely populated as the British Isles the paths of animal and man inevitably cross at many places, so I conclude with an account of such relationships and a consideration of the measures man has taken for the control and conservation of his fellow mammals.
The growth in knowledge of the British mammals that has occurred since the publication of the previous book is due to the greatly increased number of people taking an active interest in the subject. Most of them are members of the Mammal Society which in bringing them together to present and discuss the results of their researches at its annual conferences and other meetings has greatly stimulated an interest in the scientific study of mammals. Membership is open to anyone interested; its address is Harvest House, 62 London Road, Reading, Berkshire RG1 5AS.
LHM
CHAPTER 1 (#ulink_9298fe41-0637-52b8-9616-0ef1c938a1c7)
THE MAMMALS OF THE BRITISH ISLES (#ulink_9298fe41-0637-52b8-9616-0ef1c938a1c7)
THE number of different kinds of mammal indigenous to the British Isles, and now living in them, is comparatively small. About four thousand kinds of living mammals are known to science throughout the world, but of these only forty-one indigenous land mammals inhabit our region. In addition two kinds of seal breed on our coasts, and seventeen kinds of whale and dolphin are regular inhabitants of our inshore or offshore seas, making a total of sixty.
This total, however, does not include all the kinds of mammal now living in our islands, for we have no less than fourteen kinds that have been introduced by man and have become established members of the fauna. There are moreover two kinds of bat, six kinds of whale or dolphin, and six kinds of seal that have occasionally wandered to our shores and are regarded as accidental vagrants. In addition five kinds of domestic animal have become feral – that is, have run wild – in various parts of the country, and if we add to these four kinds of indigenous mammal that have been exterminated in historic times, and one introduced but subsequently exterminated, we have a grand total of ninety-eight. This represents about one fortieth of the number of known living mammals, far less than the more than five hundred kinds of bird ‘admitted to the British list’, which represent about one fifteenth of the known kinds of bird inhabiting the world.
As might be expected in a country so densely populated by man as the British Isles, most of the mammals are small and inconspicuous so that they easily keep out of harm’s way. The majority are active only by night; those active during the day live concealed underground, in woodland and hedgerow litter, or among dense vegetation. Forty-five different kinds fall into the category of small mammals, ranging in size from the pygmy shrew to the hedgehog and the pine marten; they include the insectivores, the shrews, mole and hedgehog; the bats; all but one of the rodents, the rats, mice and voles; and six of the smaller carnivores such as the stoat, weasel, and polecat.
The medium-sized mammals are much fewer; they range in size from the rabbit to the fox, and include the leporids, the rabbit and hares; four carnivores, the fox, badger, otter and wild cat; one introduced rodent, the coypu; and one introduced marsupial, the red-necked wallaby – only nine different kinds in all. Most of them are nocturnal or crepuscular – active around dusk and dawn – and all but three lie up in underground burrows for much of the daylight hours. The brown hare lies up in a form, a slight depression among herbage or even in a bare ploughed field, in which it is remarkably difficult to detect; if disturbed it escapes from danger by its speed in running and adroitness in jinking if pursued. The mountain hare digs short burrows but usually sits at the entrance and escapes from danger by running away rather than entering the burrow; it too is remarkably inconspicuous when it sits still unless it is in its white winter coat and the ground is not covered with snow. The wallaby lies up in scrubby woodland when not grazing in the open.
Of the large mammals there are only four kinds that are indigenous to our fauna, two kinds of seal and two of deer. To these must be added five introduced kinds of deer, one semi-domesticated; the semiferal horse; and the feral sheep and goat. The only enemy these have to fear is man. The seals avoid him by hauling out only on inaccessible ocean beaches, in sea caves, on remote uninhabited islands of the western coasts, or sandbanks such as those of the Wash where no one can approach unobserved within a mile. The native red deer live in the hills and mountains of the north where there is plenty of room to flee from approaching danger, which they are quick to apprehend by scent, hearing and sight in that order. The native roe deer is a woodland animal, and by day remains hidden in thick cover from which it emerges to feed in the open at dusk and dawn. Where these animals have been introduced to other places, or have become established through escapes from parks and enclosures, they are usually nocturnal inhabitants of woodlands. The introduced fallow, sika, muntjac, and Chinese water deer avoid disturbance by man in a similar way, generally emerging from thick cover only by night or at dawn and dusk. Most of these introductions and escapes have increased greatly in numbers and distribution since the end of the war in 1945, and often live close to human habitations where, because of their secretive habits, they are seldom seen unless specially sought for. Their depredations in field and garden are more commonly seen and noticed with disapproval. The feral, miscalled ‘wild’, horses, goats and sheep live on open moors and mountains where, like the red deer, they can from afar see the approach of danger – that is, man – and can move swiftly away to safety. The feral ponies of the New Forest, however, are so used to the sight of man that they take little notice of his presence, and often approach picnickers to beg for titbits.
The whales and dolphins all fall into the category of large mammals, but as they are creatures of the seas their way of life is so different from that of the land mammals that they cannot usefully be considered as living in the British Isles.
We shall now briefly pass in review the different kinds of mammal, and their taxonomic classification, before going on to consider their habits, habitats and ways of life. We fortunately do not need to enter into minute description of their diagnostic characters and structure, or the basic details of their biology, which are all set forth with great clarity in the second edition of the Handbook of British Mammals, edited for the Mammal Society by G.B. Corbet and H.N. Southern, and published in 1977, a work indispensible to naturalists interested in British Mammals.
Many naturalists have worked out schemes of classification for animals both before and since the Swedish naturalist Carl von Linné, whose name is latinised as Linnaeus, invented the binomial system. He gave each kind of animal and plant a specific name, and grouped the species, ‘species’ being merely the latin for ‘kind’, that showed some resemblance to each other into genera, singular ‘genus’, the latin for a clan or tribe. For example he classified the rats and mice into the genus Mus, giving the specific names Mus rattus to the black rat, Mus musculus to the house mouse, and Mus sylvaticus to the wood mouse. Since his time they have been separated into different genera, but still retain their specific names.
Before the time of Linnaeus naturalists distinguished species by using cumbrous compound names often amounting to short descriptive sentences. For example, Linnaeus named the daisy of our lawns and fields Bellis perennis, whereas many earlier botanists called it ‘Bellis scapo nudo unifloro’. Early writers in English often used expressions that appear quaint to modern eyes; Edward Topsell whose ‘Historie of Foure-footed Beastes’ was published in 1607–08, heads his chapter on mice ‘Of the vulgar little Mouse’ – meaning the ‘common house mouse’ – to distinguish it from the ‘Vulgar Rat, or great domesticall Mouse’.
When species are classified into genera, the genera themselves need to be arranged into convenient groups, the genera in each having some characters in common. Thus genera are gathered into families, families into orders, orders into classes, and classes into phyla (singular, phylum). Intermediate grades such as superfamily or subfamily are often used for finer divisions of classification. Thus the mammals are put into the Class Mammalia of the sub-phylum Vertebrata of the Phylum Chordata; and the ‘vulgar little mouse’ becomes Mus musculus of the genus Mus, of the Family Muridae, of the Order Rodentia, of the class Mammalia.
Although this system of classification is linear it must not be read as though it were a genealogy or family tree in which the successive levels are the descendants of the previous ones. It is merely a convention and a convenience, at least partly determined by the necessity of representing it in only two dimensions on a written or printed sheet of paper. In nature all the living species of animal are on a single level, and can be likened to the tips of the twigs of a three-dimensional tree, of which the dead-wood in the branches, limbs and trunk represents the extinct ancestors of the living species. The analogy is the more apt because the wood ascends continuously from its origin to its utmost ramifications unlike a family tree which is inverted and where the descent is cut up into generations.
The scheme of classification for the mammals now almost universally accepted and adopted by naturalists was worked out by the American zoologist G.G. Simpson and published in 1945.
Some minor modifications have been made to it during the last thirty-five years, but it has proved so useful, and is supported by such erudite and convincing arguments, that it has become the standard system adopted by zoologists throughout the world. According to the modified Simpson’s system there are 33 orders of mammals, 14 of which are extinct; 257 families, of which 139 or 54 per cent are extinct; and 2,864 genera, of which 1,932 or 67 per cent are extinct. Thus the living species represent only a small fraction of the total that have lived since the class Mammalia evolved. The diversity and number of species in all the orders except perhaps the rodents reached their peak in the Miocene or Pliocene epochs – some twenty-five to three million years ago – since when they have declined to their present level.
In the British Isles, excluding the whales, we have mammals representing nine of the nineteen orders now living, but of these only seven are indigenous, the two others are either introduced and naturalised, or are derived from stocks of domestic animals. Our fauna is therefore no more than a small sample of the mammalian diversity that ornaments the fauna of the world. It has, moreover, not contained a larger number of orders since the land became generally habitable by warm-blooded animals at the end of the great glaciation of the Pleistocene epoch, about half a million years ago. In the preceeding epochs, before the ice ages, several other orders were represented by species of mammal that became extinct long before the present pattern of the fauna evolved.
Before we discuss the problematic origin of the present fauna we should enumerate and specify the species about which we shall be speaking. In following Simpson’s arrangement of the orders the indigenous species are necessarily not separated from those that have been introduced or are extinct.
ORDER MARSUPIALIA
The marsupials differ so fundamentally from the other mammals that they are placed in a separate Infraclass, the Metatheria, whereas the other mammals of our fauna are included in the Infraclass Eutheria. The marsupials show many unique anatomical characters, but are popularly known merely by a single one, as the mammals that carry their young in a pouch. This is not universally true, for some of them are pouchless; but in all of them the young are born at a comparatively early stage of development and thus need to be carried attached to the mother’s nipples. The marsupials are typically the mammals of the Australasian region, but in addition many species live in South America and one, the Virginian opossum, extends into North America. The living species are divided into eight families of which one, containing the kangaroos and wallabies, is represented in our fauna by a single introduced species.
Family Macropodidae
Macropus rufogriseus, the red-necked wallaby or Bennett’s wallaby, is a medium sized kangaroo-like animal weighing up to about 30 pounds, sometimes nearly 50 pounds. It is native to south-eastern Australia and Tasmania; but as it is easily kept in captivity it is commonly exhibited in zoos and parks of many lands, whence it sometimes escapes. Small feral populations of that origin have become established in Sussex and Derbyshire; smaller colonies deliberately introduced on Herm in the Channel Islands, and on Lambay Island off the coast of Co. Dublin in Eire have died out. Although the English populations have been established for over thirty years they remain small because wallabies are liable to suffer heavy mortality in severe winters.
ORDER INSECTIVORA
The insectivores are mostly small mammals characterised by many primitive or generalised mammalian characters. They are considered to be descended with least change from the ancestral stock of the mammals, though all living species have various specialised adaptations. Insectivores live in most parts of the world except Australasia and South America; they include the tenrecs, hedgehogs, moles, desmans, and shrews.
Family Erinaceidae
Erinaceus europaeus, the hedgehog, our only mammal with prickles in its skin, is the largest of our insectivores. It is present throughout the mainland of Great Britain and Ireland and is common in lowland areas, particularly in the suburbs of towns. It is also found in many of the islands, but has probably been introduced into most of them by man. It lives in woods and hedgerows, coming into the open to feed as night falls. The hedgehog and the dormouse are our only mammals besides the bats that hibernate in winter.
Family Talpidae
Talpa europaea, the mole, is our only mammal that spends nearly all of its life underground. Its cylindrical body, some five to five and a half inches in length, is covered with black velvety fur. The fore limbs and their muscles are highly adapted for tunnelling in the earth, and the strongly clawed hands are broadened internally by an extra bone, the radial sesamoid. The hind feet are similarly but less conspicuously reinforced by an accessory sesamoid bone. The eyes are minute and hidden by the fur, and there is not an ear pinna, but the long snout is plentifully supplied with special touch organs. The sites of mole burrows are shown by the conspicuous heaps of earth pushed up to the surface as the mole digs its underground tunnels, in which it spends most of its life feeding mainly on earthworms which fall into the burrows. Moles are present throughout Great Britain but not Ireland or the Isle of Man; they are not found on many of the smaller islands except Anglesey and the Isle of Wight, Alderney and Jersey.
Family Soricidae
The shrews are small mouse-like animals with velvety fur, long pointed snouts, small eyes and ears. They are insectivorous and carnivorous, generally seeking their food under thick vegetation and litter below which they have runways; some species dig burrows. The first incisor teeth are large and project forwards, acting like forceps in picking up small food objects; the back teeth bear sharp pointed cusps. Shrews need comparatively large quantities of food, and are consequently active by day and night, alternating short periods of activity and rest throughout the twenty-four hours. They soon die of starvation if denied food for a few hours.
The genus Sorex contains two British species, the common shrew, S. araneus, and the pygmy shrew S. minutus, the latter being our smallest British mammal. The enamel of the tips of the teeth is red in both species, which are distinguished by size, relative length of tail which is longer in the pygmy shrew, and colour of the fur, darker in S. araneus but lighter in S. minutus. The common shrew is found throughout England, Scotland and Wales and on many of the islands, but is absent from Ireland, Orkney, Shetland, the outer Hebrides and Man. The pygmy shrew, although less abundant, is found throughout the whole of the British Isles except Shetland, the Scilly and Channel Islands. The common shrew is peculiar in showing chromosome polymorphism, that is, the number and form of the chromosomes differs in animals from different parts of the country.
Both species are annuals: young born in one summer breed in the next and die in the following autumn, so the winter population consists entirely of immature animals, and none normally lives through a second winter.
The water shrew, N. fodiens, is the only British species of the genus Neomys, and is easily distinguished by its larger size and the black colour of the fur on the upper parts; it too has red-tipped teeth. Although it is aquatic and has fringes of stiff hairs on feet and tail that aid in swimming, it is nevertheless often found at considerable distances from water in woods and hedgerows in similar places to those inhabited by other shrews. It lives in burrows in the banks of clear streams and ponds; when it enters the water the fur traps air so that it appears silvery. The fur nevertheless soon becomes wet and is dried on landing by squeegeeing through the tight fitting burrow. Its food consists of invertebrates and even creatures as large as itself such as frogs and small fish. It is found throughout the mainland but is absent from Ireland, Isle of Man, and the western and northern islands of Scotland. The water shrew is unique among British mammals in being the only one with a poisonous bite, because the submaxillary salivary glands contain a venom that paralyses small prey.
The other two species of British shrew belong to the genus Crocidura, at once distinguished from the rest by their white teeth. Their ears are larger than in the others, and the tails bear a number of long scattered hairs. They are found only in the Scilly and Channel Islands, where they live in habitats similar to those of the common and pygmy shrews. The lesser white-toothed shrew, C. suaveolens, is found on most of the Scilly Islands, Jersey and Sark; it was probably unintentionally introduced into Scilly from the continent by man. The greater white-toothed shrew, C. russula, is found only on Alderney, Guernsey and Herm in the Channel Islands. The water and greater white-toothed shrews reach a life span of eighteen months or a little more, but the lesser white-toothed shrew is as short-lived as the common and pygmy shrews.
ORDER CHIROPTERA – BATS
All the British bats are comparatively small animals, and all are solely insectivorous, and nocturnal or crepuscular. They generally catch their food on the wing but some carry their larger prey to habitual perches to eat it. During darkness they find their prey by echolocation or ‘sonar’, emitting pulses of high frequency ultrasound which are reflected back from surrounding objects to give a mental image probably similar to that produced by sight in other animals. The horseshoe bats emit pulses through the nostrils, the other species through the open mouth. All species hibernate during the winter, and become torpid for four or five months, though not continuously, for hibernation is interrupted by short periods of activity. Bats are long-lived in comparison with other small mammals, reaching an age of four or five, and sometimes over twenty years.
Fig. 1. Side and front views of the head of a horseshoe bat to show the details of the nose-leaf.
Family Rhinolophidae
Two species of this family are members of the British fauna, the greater and lesser horseshoe bats, Rhinolophus ferrumequinum and R. hipposideros. They are characterised by the possession of ‘nose leaves’, thin fleshy outgrowths arising round the nostrils but overlapping the fur of the face with their free outer parts. Their structure is complex and better described by a drawing than by words; the part over the muzzle and round the nostrils is crescentic in shape, hence the English, Latin, and latinised Greek names of these bats.
The nose leaf is part of the special echolocation system. The greater horseshoe bat has a wingspan of 34 to 39 centimetres and is thus one of our larger bats. Its natural roosts are in caves, but it also uses mines and the cellars and roof spaces of buildings. In the British Isles it is found only in southwest England and south Wales. The lesser horseshoe bat is one of our smaller species, with a wingspan of only 22 to 25 centimetres. It roosts in similar places to those used by the larger species, and has a larger range, being found in southwest England, all of Wales and extending into Yorkshire, and far to the west in western Ireland.
Family Vespertilionidae
All the other British bats belong to this family – fifteen species in seven genera. They are mostly small to medium-sized bats but the serotine and noctule equal the greater horseshoe in wingspan, and one, the rare mouse-eared bat exceeds it by up to six centimetres.
Of the fifteen species, six are common throughout much of the British Isles, though only one, the pipistrelle, is found everywhere except in Shetland; they are the whiskered, Natterer’s, Daubenton’s, noctule, pipistrelle, and long-eared bats. Five species are rare, or occasional vagrants – Bechstein’s, the mouse-eared, parti-coloured, Nathusius’ pipistrelle, and the grey long-eared bats. The remaining four species are intermediate, having a limited distribution within the bounds of which they may not be scarce. They are Brandt’s, the serotine, Leisler’s and the barbastelle bats.
Six species of the genus Myotis are British. The whiskered bat, M. mystacinus, is a small dark grey bat that roosts in trees and buildings and often hibernates in caves. It is found throughout England, Wales and Ireland, but is less common in southern Scotland and absent from the north. Brandt’s bat, M. brandti, so closely resembles the whiskered bat that it has only recently been recognised as a separate species, differing slightly in details of the ear and teeth; it is known from many parts of England and Wales but its overall distribution has yet to be ascertained. Natterer’s bat, M. nattereri, is larger, with a wingspan of up to 30 cm, and the fur brown above and light or white below. It can be distinguished from all others by the fringe of stiff short hairs along the edge of the bare skin joining the legs and tail – the interfemoral part of the patagium or double layer of skin that makes a bat in effect an aerofoil. It roosts in trees, buildings and caves throughout the British Isles as far north as central Scotland. Bechstein’s bat, M. bechsteini, very similar to Natterer’s bat but having longer ears and lacking the fringe of hairs on the interfemoral patagium, is a rare woodland bat that has occasionally been found in southern England, mostly in Dorset. The mouse-eared bat, M. myotis, our largest species with wingspan up to 45 centimetres, was known only as a rare vagrant until 1956 when a small colony was found in a cave in Dorset; another was found in Sussex fifteen years later. Daubenton’s bat, M. daubentoni, is medium in size, dark brown above and pale grey below. The ear is comparatively short, and the feet large. It is often seen catching insects flying low over water, but is by no means confined to this way of feeding and frequently hunts in other places. It roosts in hollow trees and buildings, and often hibernates in caves. It is found throughout the British Isles except the northern parts of Scotland and the Hebrides.
Of the genus Vespertilio only the parti-coloured bat, V. murinus, has been found in the British Isles, as a very rare vagrant from the continent. It is a medium-sized bat; the dark brown hairs of the back have white or buff tips which give a grizzled or speckled appearance. Similarly, the genus Eptesicus has only one British species, the serotine bat, E. serotinus, which is, however, a regular though localised member of the fauna. It is a large species with a wingspan of up to 38 centimetres, and has dark brown fur, paler below. It is mainly a woodland species but often roosts in buildings; in England it is found only in the southern and eastern counties as far north as the Wash.
Two species of the genus Nyctalus, the noctule N. noctula, and Leisler’s bat N. leisleri, are widespread though not universal in the British Isles; both have comparatively narrow pointed wings. The large noctule with a wingspan of up to 39 centimetres has dark yellowish or reddish brown fur. It is a woodland bat, roosting in holes in trees, and often flies well before dark, hunting high above the trees. It occurs throughout England and Wales, rarely in southern Scotland and is absent from Ireland. The smaller but similar Leisler’s bat on the other hand is found throughout Ireland but has a more restricted distribution in central and southern England. It, too, is a woodland bat, differing from the noctule not only in its smaller size but also in the colour of the fur on the back, which is reddish brown at the surface but dark brown at the bases of the hairs.
The pipistrelle, Pipistrellus pipistrellus, a small bat with a wingspan not over 25 centimetres, is our commonest species, being found throughout the British Isles with the exception of Shetland. It varies greatly in colour, ranging from rufous through shades of brown to almost black. It roosts commonly in buildings, in which its colonies may number several hundred animals. The closely similar Nathusius’ pipistrelle, P. nathusii, is slightly larger, but is known only as a vagrant, a single specimen having been found in Dorset in 1959.
The barbastelle, Barbastellus barbastellus, the only British member of its genus, is a medium-sized bat with black fur, the lighter tips of the hairs giving a frosted appearance. The ears are short but wide and joined at their bases above the face, thus differing from all other British species except the long-eared bat. Barbastelles roost in hollow trees and buildings, and sometimes hibernate in caves. The species is rather thinly distributed over England and Wales as far north as Cheshire and Yorkshire, and is generally regarded as uncommon.
The long-eared bat, Plecotus auritus, is a small species recognised by its enormously long narrow ears which are nearly as long as the head-and-body. When asleep it tucks the ears under the wings leaving the tragus, the lobe representing the ear-cover, of each side sticking up like a pair of spikey horns. It roosts in trees and buildings and frequently hibernates in caves; when feeding it often hovers to pick insects off the leaves of trees. It is widely distributed throughout the British Isles except in northern Scotland and most of the Scotch islands. The very similar grey long-eared bat, P. austriacus, slightly larger, greyer, and with broader ears, has only recently been recognised as a separate species. It has been found in the south of Dorset, Hampshire and Sussex, but may prove to be more widely distributed after further study.
ORDER LAGOMORPHA
This order contains the rabbits and hares, easily distinguished from rodents by the presence of a second pair of small upper incisor teeth immediately behind the large first pair. There are three British species. Oryctolagus cuniculus, the rabbit, has long been an established member of the fauna although it is not indigenous. It was introduced by man a little before A.D. 1200 from its native Iberian peninsula and north Africa to be raised in confinement for fur and meat; it subsequently escaped, became feral and increased so that it is now found everywhere in the British Isles. The myxomatosis epidemic of the 1950s reduced the population drastically, but numbers have now recovered in many places.
We have two species of hare, the brown hare, Lepus capensis, and the mountain hare, L. timidus, both considerably larger than the rabbit, and with longer, black-tipped ears and longer legs. Linnaeus named the only hare found in Sweden in his time L. timidus, and a species from South Africa L. capensis, not knowing that the brown hare of Europe differs from the mountain hare, or that its range extends from South Africa to most of Europe and much of Asia – hence the peculiarity that our native brown hare takes its scientific name from the Cape of Good Hope. The brown hare, distinguished by the black upper side of the tail, is found throughout England and Wales, southern and north-eastern Scotland. It is not native to Ireland, but has been introduced into the north, and also into many of the Scotch islands. The mountain hare is smaller, has shorter ears, and the upper side of its tail is not black. After the autumn and winter moult the coat is wholly or partly white, and becomes brown again with the spring moult. The mountain hare is indigenous to the highlands of Scotland and all of Ireland. The Irish mountain hare is considered to be a distinct subspecies slightly larger than the Scotch, and assuming a white coat incompletely or not at all during winter. Mountain hares have been introduced into parts of southern Scotland and some of the islands, the Peak district and north Wales.
ORDER RODENTIA
The rodents comprise the rats, mice, squirrels, beavers, porcupines, and cavies. They are mostly small to medium-sized animals, the largest, the Capybara, a huge cavy of South America, reaching a weight of over a hundredweight; few others approach this size. There are about 1,500 species of rodents; Simpson
remarks that they are ‘believed to be as abundant individually and in variety as all other mammals put together.’ Fortunately we have only fifteen species living in the British Isles, eight of them introduced; one introduced and one indigenous species are extinct. The incisor teeth of rodents, separated by a long gap from the cheek teeth, are single upper and lower pairs with chisel-like cutting edges and long roots from which growth is continuous so that the loss by wear at the cutting edge is perpetually made good.
Family Castoridae
The beaver, Castor fiber, was exterminated in the British Isles about AD 1200, but had been scarce long before. It was abundant in the Fens during prehistoric times.
Family Sciuridae
The red squirrel, Sciurus vulgaris, our only indigenous species, is typically an inhabitant of coniferous forests, especially those of our only indigenous pine, Pinus sylvestris, though not confined to them. The fur is reddish brown above, white below, the tail is long and bushy, and in winter tufts of long hair on the ears are conspicuous. The hairs of the tail and ear tufts wear and bleach during spring and summer, leaving the tail almost white and the ear tufts sparse. The numbers of red squirrels have varied widely during the last 300 years, but reached a peak at the turn of the century since when they have declined again. It is now widespread in much of Scotland, Ireland, Wales and northern England, but extinct in most of southern and central England. The causes of the fluctuation in the size of the population are not known.
The grey squirrel, Sciurus carolinensis, was introduced from North America and irresponsibly released in various places in the last quarter of the nineteenth century and the first of the twentieth. It has spread widely, and is now found in most of England and Wales, central Scotland and central Ireland. It is larger than the red squirrel, and has proportionally larger ears without conspicuous tufts. The fur is grey with yellowish brown streaks on the sides and feet and, in the winter coat, on back and head. The grey squirrel lives in woods of broad-leaved trees as well as of conifers; some town people regard it as an attraction in public parks, but in the country it is so destructive to young trees, fruit, forestry, agriculture and horticulture that it is now illegal to import or to release grey squirrels or keep them in captivity. Legislation, however, came too late to rid us of this pest.
Family Cricetidae
There were five species of voles in the British Isles, one probably introduced, and another that was injudiciously introduced but successfully exterminated. The last was the musk rat, Ondatra zibethicus, which escaped from fur farms, to which it had been brought from its native America. It became established in several districts about 1930, but a great official effort of destruction eliminated it seven years later.
The British voles are small mouse-sized animals with one exception, the water vole, often called the water rat from its larger size. The voles are distinguished from the mice by the rounded or blunt rather than pointed profile of the snout, and the comparatively small ears partly concealed in the fur. The diagnostic character of the different species is given by the pattern of the cheek teeth. Our four species are classified into three genera.
The bank vole, Clethrionomys glareolus, is recognised by the chestnut red fur of the upper side. It lives mostly in woodland, scrub and hedgerows, under which it makes runways and burrows, but it also habitually climbs among the branches of shrubs and small trees – so much that the late Oliver Hook, the well-known naturalist, nicknamed it ‘Cleth the Climber’, though the wood and yellow-necked mice are at some times and in some places equally or even more arboreal
. The bank vole is often a destructive pest in country gardens. It is found all over the mainland of Great Britain, and on many of the islands, but is not indigenous in Ireland where it has recently been introduced, perhaps by some zoological practical joker, and now occupies a large area in the south-west. Four sub-species are recognised, each confined to a separate island – Raasay, Mull, Skomer, and Jersey. All are larger than the mainland race, and that of Skomer is much brighter in colouration.
The field vole, Microtus agrestis, is of smaller size but has greyish brown fur, smaller ears, and a short tail. It lives mainly in rough grassland and less often among scrub and dense cover; it makes runways and builds its nests under the thick mat of grasses, the stems and leaves of which form the greater part of its food. It is found throughout the mainland of Great Britain and on many of the Hebrides, but not in Ireland, the Isle of Man, Orkney or Shetland.
The voles of Orkney and Guernsey are slightly larger and darker, and differ from the field vole by a detail in the pattern of the cheek teeth. They are a separate species, M. arvalis, common on the Continent whence they were probably accidentally introduced into the islands long ago.
Our largest vole, the water vole Arvicola terrestris, about the size of a rat, lives near rivers, ponds and canals, into the banks of which it burrows to make its nest. Although it feeds mainly upon the grass growing near the banks it readily dives into the water and swims well. Its colour is generally brown, but populations of black water voles are present in north Scotland and East Anglia. The water vole is found throughout the mainland of Great Britain but is rare in north-west Scotland, and is absent from most of the islands and from Ireland. The paradox of a water animal having the scientific name ‘terrestris’ is due to the habits of this vole on the Continent, where it is not confined to the neighbourhood of water.
Family Muridae
The mice and rats differ from the voles in having proportionally larger ears and eyes, more pointed snouts, and longer tails. The cheek teeth differ in having low crowns with cusps. We have three indigenous and one introduced species of mouse, and two introduced rats.
The wood mouse, Apodemus sylvaticus, brownish yellow above and nearly white below, often with a coloured spot on the chest, was formerly called the ‘Long-tailed Field mouse’. It lives wherever there is cover, especially in woodlands and hedgerows and consequently is found throughout the British Isles and off-lying islands into many of which it was probably accidentally introduced by man. A large number of subspecies has been described none of which are now held to be valid. Although primarily vegetarian the diet is very varied and includes many small invertebrates.
A. flavicollis, the yellow-necked mouse, closely resembles the wood mouse but is larger and has a yellow band across the chest joining the colour of the upper side. It is found in many parts of England south of the Humber, and in Wales, but is absent elsewhere. It lives in similar places to the wood mouse, but more frequently comes into houses in autumn and winter. It was not recognised as a member of the British fauna until 1894.
The harvest mouse, Micromys minutus, is the smallest British rodent. Gilbert White of Selborne, the first naturalist to note its presence in England, wrote in 1768
that he found two of them just counterbalanced ‘one copper halfpenny, which is about the third of an ounce avoirdupois’ or six to the ounce – they must have been thin mice for the average weight is about 6.0 grams or just over four to the ounce. The fur of the upper parts of the harvest mouse is bright reddish yellow and of the underside white. The nose is rather blunt, the hairy ear rather small, and the tail is prehensile. Harvest mice live among tall ground plants such as long grass and rough herbage among the stems of which they climb to seek their food and where they make globular breeding nests in summer up to about two feet above ground; in winter they live among the litter below. They are found, sometimes in abundance, throughout most of England and much of Wales, but are absent from the greater part of Scotland and the whole of Ireland.
The house mouse, Mus domesticus* (#litres_trial_promo), has dull brownish grey fur, slightly lighter below, occasionally much lighter. Unlike the other mice it has an unpleasant smell resembling that of acetamide. It is found wherever there are human habitations throughout the British Isles, feeding upon and spoiling man’s stored foods. It also occurs in hedgerows and fields away from buildings. It was introduced from the continent, no doubt unintentionally, about 2,000 years ago. Both the British species of rat are introduced, the ship or black rat about 900, and the brown or common rat about 250 years ago.
The ship rat, Rattus rattus, is commonly black in colour, but also occurs as two other forms, brown with grey underside or brown with nearly white underside. It was once widespread but is now found, with few exceptions, solely in the neighbourhood of sea ports, where it lives only in buildings.
The common rat, Rattus norvegicus, is larger than the ship rat and has comparatively smaller eyes and ears; the fur is greyish brown, lighter beneath. It lives in buildings of all sorts but also inhabits rubbish tips and hedgerows far from them. In addition it commonly lives in the open on the coast, especially on the shores of estuaries and salt marshes. It is found throughout the British Isles and off-lying islands, having replaced the once abundant ship rat. Charles Waterton, the early nineteenth century naturalist of Wakefield, expressed
his extreme Jacobin loyalty by calling the common rat the ‘Hanoverian rat’ because it was introduced soon after King George I’s accession in 1714 – a name that was sometimes used by other writers.
Family Gliridae
Our only native member of this family is the dormouse, Muscardinus avellanarius, distinguished by its orange-brown fur, long whiskers, and hairy, almost bushy tail. It lives in broad-leaved woodlands, coppices and overgrown hedgerows, building a globular nest of bark fibre, grass, and leaves several feet, sometimes yards, above ground among shrubs. Apart from the bats the dormouse and the hedgehog are the only indigenous British mammals that hibernate; the winter nest is usually made underground or among litter at ground level. The dormouse occurs sparsely throughout England and Wales, becoming scarcer in the north, and is absent from Scotland and Ireland. Another member of the family, the fat dormouse, Glis glis, was introduced at Tring in Hertfordshire in 1902, and has since persisted and spread over a small area of the Chiltern Hills. It closely resembles a small grey squirrel, but has dark rings round the eyes. It inhabits woods, orchards and gardens, and, like the common dormouse, it hibernates, often in the roofs of houses.
Family Hystricidae
The large South American coypu, Myocastor coypus, which produces the fur known commercially as ‘nutria’, escaped from fur farms in the early 1930s and established feral populations in several places, mainly in East Anglia. It is a large aquatic rodent reaching a length of a yard from nose to tail, looking like an enormous brown rat with webbed hind feet, blunt nose, small eyes and ears, and orange coloured enamel on the front of the incisor teeth. In East Anglia the population increased enormously in spite of heavy mortality in severe winters, so that the animals became a pest to agriculture and a threat to the stability of river banks. Since the early 1960s official control measures have greatly reduced its numbers.
ORDER CETACEA
Although seventeen species of whales and dolphins have been recorded as British, mainly because they have been found stranded on our coasts from time to time, they cannot be regarded as part of the British fauna as dealt with here – the wreck of a foreign ship on our coasts does not give its crew British nationality or make it part of the native population.
ORDER CARNIVORA
Of the ten indigenous species of beasts of prey two have been extinct for centuries; the remaining eight have been joined by a recent introduction derived from animals escaped from fur farms.
Family Canidae
The wolf, Canis lupus, was exterminated some 500 years ago in England and Wales, but survived in remote parts of Scotland and Ireland for another 250 years. Its descendent, perhaps with an admixture of other ‘blood’, the domestic dog, has some effect upon the country’s ecology, killing according to one authority
some 6,000 sheep a year – in 1978 4,639 were killed and 3,833 injured – and every day depositing 500 tons of dung and a million gallons of urine ‘on Britain’s pavements and parks’, equal to the sewage from four million people.
On the other hand the fox, Vulpes vulpes, is found everywhere in Great Britain and Ireland and in some of the islands. Its abundance is due to its adaptability to various habitats and foods, to its nocturnal and crepuscular habits, and to its tolerance of the near neighbourhood of man as shown by its recent extension of habitat into the suburbs of towns.
Family Ursidae
The brown bear, Ursus arctos, has been extinct in the British Isles for a thousand years; its natural distribution covers all of northern Europe, Asia and America. It varies greatly in size, from the comparatively small European race to the enormous ‘grizzlies’ of Kodiak Island off the Alaskan coast, as large as the ‘Cave bear’ that lived in the British Isles before the last glaciation of the Pleistocene epoch.
Family Mustelidae
The family consists of small to medium-sized carnivores, the British species characterised by long bodies and short legs. The pine marten, Martes martes, as large as a rabbit, with deep brown fur, a yellow patch on the throat, and long bushy tail, is an inhabitant of woodlands, where it feeds mainly on small birds and rodents. It is an agile climber. It was formerly found throughout the British Isles but has long been extinct except in northern Scotland, the Lake District, north Wales and Ireland.
Although the pine marten has been successfully destroyed as vermin in most of Great Britain, two other species, the stoat and the weasel, both subjected to similar persecution, have been able to remain plentiful. The larger of the two, the stoat, Mustela erminea, with head and body length of about a foot in males but some two inches shorter in females, is brown above, off-white below, and has a black tip to the tail. In the northern part of its range the winter coat is white with black tail tip; but in the southern part it resembles that of the summer; partly white examples occur in winter between the extremes of its range. Stoats are found throughout the British Isles and on some of the off-lying islands; those in Ireland, being smaller and having less white below, are recognised as a separate subspecies M.e.hibernica.
The weasel, M. nivalis, about four inches shorter than the stoat in both sexes, is similar in colour but does not have a black tail tip. The winter coat is not white in British weasels, though further north on the continent it is. Weasels feed mainly on voles and mice, whereas stoats take larger prey as well, especially rabbits. They are found throughout the mainland of Great Britain and some of the islands, but not in Ireland.
The polecat, M. putorius, is larger than the stoat but similar in build; the fur is brown with a white patch on the face between eyes and ears, the two often joining to form a bar. There is a white patch under the chin extending up onto the muzzle, and the edges of the ears are white. The ferret is a domesticated form of the polecat, perhaps with some hybridisation with the Steppe polecat of eastern Europe which may be specifically different; as it breeds successfully with the polecat, and some specimens cannot be distinguished either by colour or skull structure, the specific name, M. furo, for it seems superfluous. Albino ferrets are popular with the breeders and users of these animals. The polecat is an unselective carnivore; it was exterminated as vermin over most of Great Britain by the beginning of the twentieth century, but remains common in the greater part of Wales and the Welsh Marches.
The mink, M. vison, a native of North America, escaped from fur farms and became established as a feral member of our fauna in the 1950s; it is now widespread in Great Britain and common in many places – it is also present less widely in Ireland. The mink, about the size of a polecat, with a rather bushier tail, has very dark brown fur with white spots on the chin and throat. It is an unselective carnivore, and the effect of its activities on the native fauna has yet to be assessed – it may not be as destructive as some people have feared.
The well-known badger, Meles meles, grey above and black below, with a fore-and-aft black streak over eye and ear on each side of the white head, is found throughout the mainland of the British Isles and on some of the islands, and is common in many parts. It is a comparatively large animal – weights of over 35 pounds have been recorded – and is so widely spread because it is adaptable to many different habitats, has discreetly retiring habits, and is omnivorous, eating anything from earthworms to rabbits and from fruit, bulbs, and nuts to corn and grass. It comes out to forage at night, remaining underground in its set by day.
The otter, Lutra lutra, on the other hand is restricted in habitat to the neighbourhood of water, and, though formerly found throughout the British Isles and the off-lying islands, is consequently much less common than the badger; since about 1950 it has declined greatly in numbers over most of mainland Great Britain, but it is still plentiful in western Scotland, Ireland, much of Wales and south west England. The aquatic habit of the otter is shown by its webbed feet and broad snout with long tactile whiskers. The fur is brown all over, lighter on the throat, and the tail is long and tapering. The diet of the otter consists mainly of fish, freshwater or marine, for in the west of Scotland it is as much an inhabitant of the sea shore as of fresh waters.
Family Felidae
The wild cat, Felis silvestris, somewhat larger than most domestic cats, is a tabby with dark cross stripes on a grey background, and bushy tail ending in a rounded, not pointed, black tip. It has long been extinct in most of Great Britain and is now found mainly in the highlands of Scotland where it is extending into its former range; it was never native to Ireland. Its food includes rabbits, hares, rodents, and birds. It has hybridised much with feral domestic cats – domestic cats both feral and tame are probably the most destructive of all predators to the small mammals and birds of our fauna.
ORDER PINNIPEDIA
The seals are only marginally part of our fauna, for they are confined to the waters off the coast and to the sea shore from which they come a short way onto land only in remote undisturbed islands. They are, however, animals of particular interest to zoologists, and of unusual endearment to the public in general. Two species live and breed on British coasts; five others are merely accidental vagrants from northern seas, and thus form no regular part of our fauna.
Family Phocidae
The common seal, Phoca vitulina, and the grey seal, Halichoerus grypus, are not easy to tell apart when in the water, unless very close to the viewer. The coat colour of both species varies greatly; the basic pattern is of dark spots on a grey background, the spots tending to be smaller in the common seal, but no two individuals are exactly alike. Bull common seals reach a length of two metres overall, cows about 20 cm less, whereas bull grey seals reach three metres but the cows some 45 cm to 60 cm less. The snout of the common seal is comparatively short, giving the head a rounded appearance and a ‘dished’ profile; in the grey seal it is long and high, giving a convex profile to the head. Both species can be found on many parts of our coasts, but concentrate in special places to form breeding colonies. The common seal is least likely to be met with on the southern and western coasts of England and Wales; it breeds at several places on the east coast, especially in the Wash, in Orkney and Shetland, on the west of Scotland and the islands, and the east of northern Ireland. On the east coast of England the main breeding colony of the grey seal is at the Farne islands; in Scotland it abounds in Orkney and Shetland and many islands of the west. There are also breeding colonies on the coasts of Wales, Cornwall, and much of Ireland. The common seal prefers shallow waters with sand and mudbanks and is often found in estuaries, whereas the grey seal lives in deeper waters off rocky coasts. Both species come ashore to give birth, the young of the grey seal remaining on or above the beach for about their first three weeks, but those of the common seal, born on sand or mudbanks covered at high tide, swim with their mothers from the first.
ORDER PERISSODACTYLA
Family Equidae
Wild horses have been extinct in the British Isles for about 10,000 years, but half-wild breeds derived from introduced domestic horses exist in several districts of extensive unenclosed land.
ORDER ARTIODACTYLA
Family Suidae
The wild boar, Sus scrofa, has been extinct in Great Britain for some 300 years. Although its domesticated descendants have played an important part in the rural economy of Ireland it was never indigenous there.
Family Cervidae
Stags of the largest of our two native species of deer, the red deer Cervus elaphus, stand up to about four feet at the withers, hinds about six inches less. The coat colour varies greatly; in general it is red-brown in summer, grey-brown in winter, with a white patch on the rump. Calves at birth are reddish-brown with white spots, but lose the spots at their first moult at the age of about two months. Horns, now generally called antlers, a term originally meaning the branches or tines, are carried only by stags. They are dropped from the pedicles, from which they grow on the forehead, in spring or summer, whereupon new ones at once start growing and are complete by the autumn. The red deer, formerly present throughout the British Isles, remains as a truly wild animal only in Scotland, the Lake district, on Exmoor and the Quantock Hills, and in south-west Ireland; elsewhere feral deer, often derived from escaped park animals, are present in many places. In Scotland the deer are animals of the hill, but in lowland England they are more generally inhabitants of woodland where they reach greater size and the stags bear larger antlers.
The sika deer, C. nippon, smaller than the red deer but similar in build, was introduced from the Far East in the second half of the nineteenth century, and feral populations have become established in a number of places in the British Isles. The coat is red with light spots in summer, darker and unspotted in winter; the rump patch and tail are white except for a narrow black line on the latter. The antlers of the stags are smaller and have fewer tines than those of the red deer, and lack a bez tine between the brow and trez tines. Sika deer inhabit woodlands from which they come out to graze from dusk to dawn. They hybridize freely with red deer where the ranges of the two species overlap.
The fallow deer, Dama dama, is another introduced species, but has been adopted into our fauna for a much longer time – probably almost a thousand years. It has for long been a favourite ornament in parks from which it has escaped so that feral populations are widespread in England, Wales and Ireland, and are found in some parts of Scotland; those in Epping and the New Forests probably represent the early stock. Bucks stand about three feet high at the withers, does a few inches less; the antlers of the bucks are usually handsomely palmated. The colour varies greatly but is light with spots in summer, much darker and generally without spots in the winter. The border of the white rump patch is black, as is the upper surface of the tail.
The roe deer, Capreolus capreolus, is a true native of Great Britain but not of Ireland. It is plentiful in Scotland and northern England, but has been introduced into southern England, and into East Anglia where it was exterminated some two hundred years ago. It is a small deer, barely two feet six inches at the withers, with no visible tail. The colour is tawny red, the muzzle black and the chin white; in the darker brown winter coat two white patches appear on the throat. The antlers of the buck are short spikes each with one forwardly directed tine at the base and a backwardly directed one at the top. Roe live in woodlands, which they leave to browse on bushes at dawn and dusk.
Two other small species of introduced deer are at large in parts of England, descended from animals that escaped from captivity during the present century. The muntjac, Muntiacus reevesi, is widespread through much of south, central and eastern England, and is still increasing its range. It is not more than eighteen inches high at the withers; the coat is deep chestnut in colour, lighter below. The antlers are short spikes carried on long hair-covered pedicles prolonged forward as ribs on the face. Muntjac live in dense cover where they are more easily heard than seen, for they utter a short sharp bark repeated many times when disturbed. The Chinese water deer, Hydropotes inermis, is slightly larger, reddish to greyish brown, and with large ears; the bucks do not have antlers but long upper canine teeth that project from the mouth as tusks nearly three inches in length. Water deer live among long dense herbage on which they graze – they are less widespread than the muntjac, being feral but numerous in parts of Bedfordshire, Northamptonshire, Buckinghamshire, and Huntingdonshire.
Family Bovidae
Cattle, sheep and goats do not exist in the wild in the British Isles. Wild cattle, from which domestic cattle are descended, have been extinct in Great Britain for some three thousand years – the ‘wild’ white cattle preserved in several parks are derived from domestic animals. A primitive breed of sheep, the Soay breed, has long been present on the island of the St. Kilda group to which it gives its name meaning ‘Sheep island’; it is derived from domestic stock. The ‘wild’ goats that are feral on mountains or islands in various parts of the British Isles are derived from domestic animals, for the species has never been indigenous. The domestic sheep, however, has played an important part in shaping the ecological background of the British fauna, much of our so-called man-made landscape being in fact a sheep-moulded landscape.
In the chapters that follow we consider the biology of this mammalian fauna, enquire into its origin and present distribution, and investigate the way of life of its various members, and how it shares the approximately 75 million acres of its homeland with over fifty million human beings.
CHAPTER 2 (#ulink_f9ade821-4ba3-544f-9c82-62dca0722850)
ICE AGES (#ulink_f9ade821-4ba3-544f-9c82-62dca0722850)
THE small number of mammalian species now living in the British Isles is sometimes spoken of as an impoverished fauna. This is not strictly correct; it is a small fauna compared with those of some other lands, but of the forty-six indigenous species only five have been exterminated in historic times, whereas fourteen that are not indigenous have been introduced and now permanently enrich it. The causes of the present composition and distribution of our indigenous mammalian fauna must be sought in the geological history of the islands.
The basic geological structure of the country has evolved through enormous periods of time during which the rocks were laid down as deposits on the floors of successive seas, or extruded through the earth’s crust by volcanic activity. If we could see from a satellite the events forming the present topography of the earth as in a time-lapse film, so that many millions of years were concentrated into an hour, the tortured crust would appear to be in constant movement, writhing and squirming as immense forces distorted it. The tectonic plates jostling each other or drawing apart to form the oceans, pushed asunder by the material rising between them from below, were sometimes sunk far beneath the sea from which they received deposits of enormous thickness, or thrust up into mountains and lands from which erosion carried their substance back to the oceans – everything was, and still is, in constant flux. During all these upheavals plants and animals were evolving ever since life first appeared on the earth some time in the Precambrian epoch, perhaps as much as three thousand million years ago.
The successive epochs into which palaeontologists divide geological history each had their characteristic faunas and floras which left their remains as fossils in the rocks, representing a biomass, or aggregate of living matter, so great that it is almost beyond comprehension to the human mind. Among this teeming swarm the mammal-like creatures first appeared in the Triassic epoch, which began some 225 million years ago; but ten million years were to pass before the Eutheria, the placental mammals, evolved towards the end of the Cretaceous epoch. In the succeeding Eocene epoch, which began about seventy million years ago, the orders of mammals that we know as living animals were already differentiated together with others that are now extinct.
During the following epochs, the Oligocene and the Miocene, in which great crustal disturbance took place, including the upraising of the great mountain ranges, the evolution of the mammals produced a vast variety of forms which reached a peak in numbers before the end of the Miocene some twelve million years ago. In the succeeding Pliocene, which lasted about ten million years, the land masses gradually took on their present shapes, and mammalian species began to decline in number, a decline that continues to the present day. Throughout these epochs the climate varied from time to time, sometimes temperate, at others cool and wet, or warm and arid, but it was not until the Pleistocene that the greatest climatic change in later geological history took place.
The Pleistocene epoch was comparatively short; it has been deeply studied using modern techniques during the last fifty years so that our knowledge of it increases every day. It was formerly thought to have lasted about a million years, but is now known to have been probably twice as long – some authorities consider it to have lasted as much as three million years. It is popularly called the ‘Ice Age’, a name that over-simplifies the matter, for the ice ebbed and flowed so that mild periods of sometimes almost tropical warmth, separated successive glaciations. At its height ice sheets covered most of Europe, North America and northern Asia, while another covered Antarctica, as it still does.
It was in 1837 that Louis Agassiz, the Swiss and later American geologist and zoologist, first drew attention to the evidence that glaciers had once covered much of the land, evidence which he had discovered in 1836 on his field excursions in search of fossil fishes.
His views were adopted by the Reverend Dr William Buckland F.R.S., Canon of Christ Church and Professor of Geology at Oxford, later Dean of Westminster, the English pioneer geologist and palaeontologist. He found similar evidence in the British Isles, especially the grooves and scratches scored in rock surfaces of the north, over which glacial ice had flowed engraving the substrate with the burins of its entrapped stones.
Buckland was the first President of the British Association for the Advancement of Science, and when he addressed the ‘British Ass’ on the subject of glaciation one of his waggish friends drew a caricature of the great man standing on a surface covered with glacial scoriations while at his feet lay two pebbles, one of them labelled ‘specimen no. 1, scratched by a glacier thirty-three thousand three hundred and thirty-three years before the creation’; the other, ‘no. 2, scratched by a cart wheel on Waterloo bridge the day before yesterday.’
Fig. 2. Position of the ice edge at maximum cover of Eurasian glaciation during the Anglian glaciation of the British Isles.
As with all new theories before they become accepted as established truth, the glacial theory at first met with much opposition as well as ridicule – indeed Buckland himself at first strongly disagreed, and it was only during a tour of Scotland in company with Agassiz in 1840 that he was convinced. Thereafter he has strongly supported the theory and, through the evidence of glacial action on polished and scoriated rocks and the presence of morraines, most of the leading geologists of the day agreed with him. He was also the first to suggest that the famous parallel roads of Glenroy in Scotland were the former shore lines of a glacial lake formed by the damming of Glen Spean by two glaciers coming down the north and east sides of Ben Nevis.
The knowledge that the country, and later that all countries on both sides of the north Atlantic, had once been in the grip of an Ice Age stimulated geologists to more detailed research, and it soon became apparent that there had been not one Ice Age but several. The difficulties of identifying and dating them were enormous, because younger glaciations are bound to disturb, distort, and confuse the traces of older ones, as are denudation, erosion, and changes of sea level in the often long intervals between them. Local variations in the extent and intensity of glaciation further complicate the problem.
The basic pattern of the successive glaciations in Europe was appropriately worked out by investigating the glaciations of the Alps, where Agassiz had first discovered evidence of the ‘Ice Age’. About the beginning of this century Penck & Brückner
, after prolonged study of the gravel terraces laid down by rivers rushing forth from beneath the melting glaciers, concluded that there had been four main ice ages separated by long interglacial periods when the land was free from ice-cover and the climate was comparatively warm. They named the four glaciations after rivers flowing down from the Austrian alps to southern Germany, in the valleys of which they examined the fluvioglacial gravels and moraines; the oldest they named Günz, and the succeeding ones Mindel, Riss and Würm.
The last glaciation, the Würm, reached its peak about 20,000 years ago, but it was not so severe or long-lasting as some preceeding ones. During the Mindel glaciation the ice sheets reached their greatest size and covered an enormous area of Europe, much more extensive than that covered in the later Riss and Würm stages. The interglacial stage between the decline of the Mindel and the onset of the Riss lasted nearly a quarter of a million years, during which a contemporary intelligence might have thought that ice ages had gone never to return. Although the Günz was designated the oldest or first glaciation, there are now known to be indications of numerous glaciations older still, hence the differences of opinion between authorities on the probable length of the Pleistocene epoch. There cannot, in any case, have been any sharply defined boundary between the Pliocene and the Pleistocene, for the whole of geological and biological evolution is a continuous process. The boundaries between all the geological epochs are arbitrary, and are used merely as a convenience with the tacit admission that they cannot represent any specific moment in time.
The history of the Pleistocene is, however, by no means the simple and clear cut sequence as might appear from the basic pattern. During glaciations the edges of the ice sheets advance and retreat to different extents and in different places, and during interglacial periods they re-advance from place to place and retire again in an unending chain of fluctuations that bring variations in topography, climate, flora and fauna. Furthermore, the sequence worked out for the glaciations of the Alps may not correspond exactly with those found elsewhere.
Geologists of many lands studying the glaciations and alternating interglacial periods of the Pleistocene in their own countries have gone deeply into the problems of correlating their local findings with the basic alpine pattern. A general measure of success has been achieved in this though much detail remains obscure, and the sequences in Scandinavia and northern Europe and in North America are found to correspond reasonably closely. They are, as well, found to correspond with the pluvial sequences found in land further south which, though never covered with ice sheets, experienced periods of high rainfall when the ice held more northern latitudes in its grip.
Although the pattern of successive glaciations in the Alps corresponds roughly with that of other parts of Europe and elsewhere, it is in some ways a special case. Even at the maximum of glaciation when a continuous sheet of ice blanketed northern Europe and Asia and covered the British Isles and the site of the North Sea, the ice cap over the Alps was separate and not continuous with the great ice sheet. The causes of the glaciations were similar for both regions but the effects were subject to local variations; consequently the nomenclature for the Alpine glaciations is now applied less uniformly to those of regions further north, including the British Isles.
The difficulty of making exact correlations between Pleistocene events in different places has been resolved by classifying them according to local stratigraphy. Pleistocene deposits, both those of glacial and interglacial stages, are not continuous, and the geologists have to put together the history of the epoch from the examination of scattered and limited samples from many different places. The glacial and interglacial stages are named after the places where well-known deposits of each stage have been studied, and consequently the nomenclature for north western Europe differs from that for the Alps, and from that for the British Isles. Thus the last or Würm glaciation of the Alps corresponds to the Weichselian glaciation of north-western Europe, and the Devensian of the British Isles.
In the British Isles many of the typical pleistocene sites are found in East Anglia and take their names from nearby towns and villages of Norfolk, Suffolk and Essex. The last glaciation however takes its name from the Devenses, the ancient British tribe that lived over 50,000 years later in the area including Four Ashes in Staffordshire, the typical site.
The succession of deposits is not complete, so that information is lacking about the earliest Pleistocene, and for a period of about a million years in the middle Pleistocene. In spite of these gaps the deposits indicate alternating colder and warmer phases but give no unequivocal evidence of glaciation, with ice sheets covering much of the country, until comparatively late in the epoch when ice cover reached its maximum during the Anglian glaciation, corresponding with the Elster glaciation of northwest Europe and the Mindel of the Alps.
Conditions immediately after the end of the Pliocene, some two to two-and-a-half million years ago, are imperfectly known but there appears to have been a cold stage at first, represented by the Nodule Bed at the base of the Red Crag deposits of East Anglia. A gap in the record of nearly half a million years is then followed by an alternation of two warm and two cold stages represented by pre-glacial deposits of the lower Pleistocene. These are the Ludhamian (Ludham, near Norwich) warm, Thurnian (river Thurn, Norfolk), cold, Antian (river Ant, Norfolk) warm, and Baventian (Easton Bavents, near Southwold, Suffolk) cold. At the end of the Baventian stage another gap in the record lasting about a million years is followed by the warm Pastonian stage (Paston, near Cromer, Norfolk), the first stage of the middle Pleistocene, about half a million years ago.
The following Beestonian (Beeston, near Dereham, Norfolk) was the first cold stage of the middle Pleistocene and was succeeded by a warm stage, the Cromerian (Cromer, Norfolk), which lasted until the onset of the great glaciation over 450,000 years ago. This, the Anglian glacial stage (East Anglia), lasted between fifty and sixty thousand years and covered the whole of the British Isles as far south as the Thames with a sheet of ice that produced the greatest glaciation in the whole of the Pleistocene. When the Anglian stage came to an end the land was free of ice for about 185,000 years during the temperate Hoxnian stage (Hoxne, on the Suffolk–Norfolk border near Eye and Diss); in this stage the temperature was at times higher than that of the present day.
The next glaciation, the Wolstonian (Wolston, near Coventry, Warwickshire) lasted some 60,000 years from about 240,000 to 180,000 B.P. The ice cover did not extend as far south as in the Anglian stage; the ice edge ran south from northern Norfolk and then west across the midlands to the mid Welsh border, thence turning south to reach and follow the north coasts of Somerset, Devon and Cornwall. The succeeding Ipswichian (Ipswich, Suffolk) temperate stage lasted about 60,000 years until about 120,000 B.P. when the cold returned with the onset of the last, Devensian, glacial stage in which the ice covered Scotland, northern England, Wales, and most of Ireland. A large area of the midlands and east Yorkshire was thus free from ice cover, though the ice covering the North Sea encroached on the east coast as far south as Norfolk. The ice of the Devensian stage melted comparatively quickly some twelve thousand years ago so that before 10,000 B.P. the post glacial or Flandrian temperate stage was established, which extends to the present day; it takes its name from the transgression of the North Sea over the former dry land bordered by England and Flanders, when the sea level rose as the water from the ice returned to the sea.
Fig. 3. Limit of ice covering during (a) the Anglian, (b) the Wolstonian and (c) the Devensian glaciations.
In all the glacial stages there were at least two maxima of cold separated by less cold interstadial intervals, and similarly in the interglacial stages the climate fluctuated between cold, temperate, and warm. The beginnings and ends of the glacial stages were gradual, so that as the ice retreated after a glaciation the land was at first polar desert becoming steppe or tundra as the temperature rose; it was then invaded by open boreal forest with birch and pine dominant, which in turn was replaced by dense deciduous forest with alder, oak, ash and other broad-leaved trees. As a glacial stage approached the succession was reversed.
Fig. 4. Stages of the Pleistocene in the British Isles.
Apart from the climatic changes correlated with the glaciations and producing their advances and retreats, there were during the Pleistocene great changes in the level of the sea in relation to the land. The enormous masses of water withdrawn from circulation and locked up in the form of ice caused a fall in sea level of many hundreds of feet – indeed, it is reckoned that if all the ice even now in the form of glaciers and ice-caps were to melt the level of the sea would rise about three hundred feet.
On the other hand the land is depressed towards sea level during glaciation by the sheer weight of ice resting upon it. At the same time there has been throughout the Pleistocene from time to time a slow upraising or lowering of the land, the eustatic movements of the tectonic plates.
An important consequence of these changes in sea level, whether caused by withdrawal of liquid water or by movement of the land, was that the British Isles were periodically part of the continent of Europe so that they shared its fauna and flora. Thus the bed of the southern part of the North Sea has for long periods been dry land, and the final opening of the Straits of Dover did not come about until some seven thousand years ago. One cannot help wondering whether this was a sudden dramatic happening in some furious equinoctial gale when low atmospheric pressure and a high spring tide combined with a surge such as those that have brought disastrous floods to East Anglia in recent times, broke the crumbling barrier and sent the waters of the North Sea pouring over into the English Channel – or whether an unusually high tide crept over a low dune between the salt marshes on each side so that the waters met and mixed with so little fuss that no one would have noticed.
The connection with the continent facilitated the return of the flora and fauna after it had been exterminated by each glaciation. At the time of the greatest glaciation some 450,000 years ago an unbroken sheet of ice covered the whole of northern Europe, including the British Isles, except southern England south of a line joining the Thames to the mouth of the Severn.
The part left free of ice was deeply covered with winter snow, and the sea was full of floating ice. It is doubtful if any of the flora or fauna was able to live there; certainly no mammals could survive, and consequently our present fauna must have arrived after the ice of the great glaciation retreated.
Subsequent glaciations were less extensive so that the midlands as far north as York and the southern part of Ireland were free of ice and provided a possible habitat for those species that could withstand the arctic or subarctic conditions. The changes in flora and fauna are sometimes spoken of as retreats to more congenial climates in the south during the glaciations – the distribution of the plants and animals retreated, but there was no physical movement of individuals, they were merely killed. The return during interglacials was different; the flora gradually spread in by the usual manner of seed dispersal, but the animals and especially the mammals did move in ‘on the hoof’, not as mass migrations but in the course of populations extending their ranges under pressure of numbers as new habitats became available.
The amount of extermination among the mammalian species even in the last glaciation, which did not blanket the whole of the British Isles and ended some twelve to ten thousand years ago, is shown by comparing the 167 species of land mammal now living in western Europe with the 41 of Great Britain and the 21 of Ireland.
Our fauna is not so much ‘impoverished’ as incomplete; there was not a long enough period of time before the breaching of the Straits of Dover for more species to extend their range into the islands. As H. W. Bates, the naturalist of the Amazon and later for many years secretary of the Royal Geographical Society, said in 1878, the British Isles are ‘a half starved fragment of the Palaearctic’.
Many methods are now used for dating the events of the Pleistocene: geological methods such as the study of varves, the annual variation in the composition of deposits giving laminated sediments in freshwater lakes; investigation of the palaeomagnetism of rocks; and chemical methods such as radio-carbon dating of organic material derived from living organisms, and potassium-argon dating for older rocks. But in tracing the changes in the composition of the flora and fauna the discovery and study of the fossil or subfossil remains of the plants and animals themselves provides the most important evidence. If the horizons in which mammalian remains are recovered are accurately recorded it is possible to know the composition of the fauna from time to time, and to infer much about the conditions of the environment – when, for example, hippopotamuses lived in the Thames before the Devensian glaciation the climate was, presumably, much warmer than at present.
On the other hand the presence of various species of elephant need not of necessity imply that the climate was warm; the order Proboscidea, now reduced to only two species facing extermination in the not too distant future, was once numerous in species some of which were no doubt able to live in temperate or even cold climates provided there was sufficient vegetation for their food – it does not follow that all were warm climate creatures because their living relatives are. Indeed the mammoth, which was clothed in a warm coat of shaggy hair, was an inhabitant of cold regions. Similarly the woolly rhinoceros, which also had long hair, was present with the mammoth in the last cold interstadial of the Devensian glaciation.
But hair on rhinoceroses does not imply that the animals live in cold climates for the hairiest of the living species, the Asiatic two-horned rhinoceros, lives in tropical south east Asia.
The hair sticking to the frozen remains of mammoths found in Siberia is red, but may have been darker or brown in life, for the pigments in long-preserved hair, especially when buried, undergo a change towards an auburn red – the hair of Egyptian mummies often has this tinge. The hair of Ben Jonson, who died in 1637, was found to be red when his skull with hair still attached was exposed in 1859 during the reburial in Westminster Abbey of the remains of John Hunter, the surgeon and anatomist.
When the skull of Sir Thomas Browne, who died in 1682, was exhumed in 1840 the hair associated with it was ‘of a fine auburn colour’; before it was re-interred in the chancel of St Peter Mancroft, Norwich, in 1927 it was examined at the Royal College of Surgeons by H.L. Tildesley,
who remarked that ‘hair of persons long buried is commonly found to have acquired a reddish tinge, whatever the original shade.’
Our most detailed knowledge of the composition of the flora and the nature of the climate, at different times during the Pleistocene is, however, derived from the study of fossil pollen, a technique now known as palynology. In addition, a study of peat, freshwater and marine molluscan shells, and of insects, especially the wing covers of beetles, has thrown much light on the changes in climate.
The outer layers of a pollen grain are made of the substance sporopollenin which, unlike the inner cellulose layers, is extremely resistant to the action of chemical changes so that pollen grains are almost indestructible by natural agencies. Vast quantities of pollen released by plants, and especially those species that are wind-pollenated, became mixed with the soil and waters and included in the deposits and sediments. The surface of pollen grains is thrown into a great range of shapes and patterns that are characteristic of, and identify, the different species; the presence and relative quantities of pollen in any sample of Pleistocene deposit therefore show the presence and relative abundance of the plants from which they were derived. So, for example, a predominance of conifer pollen indicates a cool climate, and a preponderance of oak pollen points to a milder climate. There are, naturally, difficulties in using pollen analysis; pollen can be carried great distances by the wind, and the indestructible nature of the pollen coat itself allows pollen from old deposits to be washed out and included in younger ones. Palynology has nevertheless proved to be one of the most valuable tools in reaching an understanding of the changes during the Pleistocene.
Palynology was born in Denmark and was developed with great success in the British Isles by Sir Harry Godwin and his pupils at Cambridge so that the history of the British flora, and with it that of the environmental ecology, is now better known than that of any other area of similar size.
The earlier work of Zeuner
on the climate, chronology, and faunal successions of the Pleistocene, not only in the British Isles but throughout the world, was extended in great detail by Charlesworth twelve years later.
This immense work summarises and reviews world-wide research on the Pleistocene up to 1956, and discusses all the different theories that have been put forward to explain its occurrence and the fluctuations that took place during it.
Charlesworth points out that terrestrial causes such as deformations of the crust of the earth are not sufficient to have brought about glaciations. He favours the theory that long-term variations in the amount of solar radiation reaching the earth were the probable cause, though it may not be possible to prove their occurrence by direct observation. This hypothesis was first made by Simpson,
who suggested that an increase in solar radiation by raising the world temperature intensified the atmospheric circulation, and brought about glaciation by augmenting the amount of cloud and precipitation. Charlesworth points out that glaciation was probably produced by a number of factors, of which variation in solar radiation was only one, and that meteorological, geological, and astronomical changes ‘all interacting and so delicately balanced that a slight change, such as would be undetected by less than a century of acute observation, might induce great effects.’
As an outcome of recent studies it is now widely accepted
that major glaciations are due primarily to the positions of the continents resulting from continental drift and the movements of the tectonic plates. Ice ages can only occur when there are land masses in high latitudes on which ice and snow can accumulate – the condition of the earth today, with an Antarctic continent and an Arctic sea surrounded by land. With the continents in these positions the ‘Milankovitch effect’ comes into operation, and small regular changes in the earth’s orbit and orientation towards the sun cause the rhythmic alternation of glaciations and mild interglacial stages through the changes in the amount of heat received by high latitudes. The ‘wobbles’ in the earth’s movements are astronomically predictable, and consequently the sequence of ice ages can be shown to have occurred many times, probably twenty or more, during the Pleistocene.
Predictions warn that our present interglacial may not last more than another thousand years until it begins to decline into the next glaciation, which, at its peak after some 20,000 years will be more severe than the Devensian.
‘Little ice ages’, such as the cold period that lasted from about 1650 to 1850, occur at more frequent intervals. They are caused by a temporary decline in sunspot activity combined with an increase in terrestrial volcanic activity, which produces a veil of dust in the atmosphere that reduces the solar heat reaching the earth. Major glaciations, however, only occur when the earth periodically ‘wobbles’ to produce the Milankovitch effect.
Whatever the causes of glaciation may be, we may take it as certain that the present mammalian fauna of the British Isles originated after the end of the great Anglian glaciation nearly half a million years ago. Furthermore it seems probable that few species of mammal survived the Devensian glaciation, during which ice covered the northern part of the islands, and the southern parts were subjected to a severe periglacial climate with permafrost producing frost-tundra having little plant cover. At the end of the Devensian the succeeding Flandrian post-glacial stage saw the establishment of the mammalian fauna as we see it today, although it is now reduced by the loss of several species that have been exterminated by man.
During the last hundred and fifty years a host of geologists and palaeontologists, amateur and professional, has collected great quantities of mammalian fossils from the Pleistocene deposits, and has worked on the difficult problems of deducing the composition of the faunas of the various stages. The earlier workers did not appreciate the importance of recording the exact horizons at which they found the fossils, and consequently their specimens give less information than those collected by later workers who adopted a stricter discipline. In addition, much material collected on sea beaches came from strata exposed in the cliffs above, and cannot be accurately assigned to the horizon from which it is derived. Similarly fossil and subfossil bones found in caves have frequently been excavated without recording the precise horizon from which they came. The stratigraphy of cave deposits is complicated by the way in which the fossils were included. The remains from which the fossils are derived were often washed in by floods, or carried in by predators, so that specimens of different provenance are confusingly mixed.
The researches of many workers nevertheless combine to give a picture of the succession of faunas that can be accepted with confidence as reasonably accurate. The results are widely scattered throughout a vast literature, but the Monographs of the Palaeontographical Society
in which large numbers of mammalian fossils from the Pleistocene have been described and illustrated during the last hundred and thirty years, deserve special notice. Many authorities, too, have gathered the available information together to give an account of the Pleistocene faunas, one of the earliest being Buckland’s ‘Reliquiae Diluvianae’
published in 1823, which described fossils from caves and ‘diluvial gravel’ as evidence of ‘the action of a Universal Deluge’. A later classic is Owen’s ‘History of British Fossil Mammals and Birds’ published in 1846,
and from the nature of the material available necessarily dealing mainly with Pleistocene faunas. In contrast a modern synthesis based on the results of researches supported by the latest technologies such as Stuart’s review,
shows the complexity of the succession of faunas, and the differences in fauna with the alternation of cold and warm, glacial and interglacial stages. The following summary of events is based in part on this important work.
The deposits of the lower Pleistocene are the strata of the Red Crag, with the Norwich Crag lying above them, that cover much of East Anglia. The oldest part of the Red Crag is the Nodule Bed found at its base in several places. All are marine deposits laid down when the sea level was considerably higher than at present, sometimes as much as forty feet. The fossil bones of land mammals found in them must therefore represent animal carcases that were washed into the sea, especially by rivers in flood, and consequently may not be a fair sample of the contemporary fauna. The Red Crag Nodule Bed, however, is derived partly from the breakdown of older rocks and contains the remains of their fossils in addition to its own contemporary ones; some are derived from Pliocene or older formations and are much worn and polished by wave action.
The alternating temperate and cold stages of the pre-glacial Lower Pleistocene occupied about the first three-quarters of the epoch, some one and a half million years, leaving only half or at most three quarters of a million years for the more spectacular events of the Middle and Upper Pleistocene. The flora of the different stages, and consequently the nature of the contemporary climate, are inferred from a study of pollen analyses and the invertebrate and vertebrate faunas. Throughout this immense period of time the fauna appears to have changed little in composition. The mammalian fossils known from the deposits laid down in the British Isles during the Lower Pleistocene include giant beavers, voles, bears, a panda, hyaenas, sabre-toothed and other cats, elephants and mastodons, horses and zebras, a tapir, rhinoceros, deer and oxen, all of extinct species, together with the still existing beaver and red fox.
This list does not represent a large fauna for so long a period of time but when we remember that, with the exception of a few species known from the cave deposits in Dove Holes, Derbyshire, all are from marine deposits, it is not surprising that it is short. The carcases of animals washed into the sea soon decay and disintegrate so that the bones are scattered and the most durable parts, the teeth, are those more likely to be preserved in marine deposits. The Nodule Bed of the Red Crag, as mentioned above, contains a mixture of fossils. We can well imagine the sea eroding the cliffs of Pliocene or earlier epochs, and then rolling and polishing the released fossils on the beach until they were again buried in new deposits, just as today the fossils of the Crag can be found lying loose on the beach. Some of the fossils thus represent animals that were not members of the Lower Pleistocene fauna, for example the tapir, three-toed horse, and the panda.
The Middle Pleistocene began with a temperate stage, the Pastonian, which was followed by a cold subarctic stage, the Beestonian; this gave way to another temperate stage, the Cromerian, which preceeded the onset of widespread glaciation. The deposits of the Pastonian are marine sands and gravels known as the Weybourne Crag, the lower part of which was laid down in the Baventian stage of the Lower Pleistocene. The stages that follow are represented by the Cromer Forest Bed series which includes both marine and freshwater sediments and contains many mammalian fossils. A comparatively large mammalian fauna has been recorded from these beds; some species can be assigned to the cooler or to the temperate stages, but the exact position of many remains doubtful.
The fauna of the temperate Pastonian stage included extinct species of ground squirrel, beaver, voles, mammoth, horse, rhinoceros, deer and bison, as well as the still existing wolf, otter, wild boar and hippopotamus. Some of these species may belong to the succeeding cold Beestonian stage when the ground was frozen with permafrost in places, but it has not been possible to reconstruct the mammalian fauna of the stage; it was probably reduced in variety and confined to arctic species.
The rich fauna of the temperate Cromerian stage has yielded a great quantity of fossils that have been collected and studied for nearly two hundred years. Many of them, however, cannot be assigned to the various zones into which modern research has divided the stage because, as already mentioned, the early collectors did not appreciate the importance of recording the exact horizons from which they took their specimens. The mammals living during this stage included a monkey, many different species of rodent large and small, many carnivores from wolf and red fox to hyaenas, lion and sabre-tooth. The ‘big game’ were well represented with elephants and mammoth, horses and zebras, rhinoceros, wild boar and hippopotamus, giant and smaller deer, bison, aurochs, musk ox and sheep.
Some of the species of this extensive list are typical of colder climates such as the ground squirrel, pine vole, glutton, and musk ox; and others of warmer ones such as the monkey, spotted hyaena and hippopotamus. The majority, on the other hand, are species that might live under a temperate climate like that of the present day in the British Isles. When the Cromerian stage drew towards its end the climate became cooler, and mixed oak forest was replaced by boreal forest with pines and birch, and with open heaths, until the Anglian glacial stage wiped out most of the flora and probably all of the mammalian fauna. The history of the present mammalian fauna of the British Isles must therefore start at the end of the Anglian glaciation, which wiped the slate clean for a new start, leaving us only a few tons of fossil bones from which to infer what had gone before.
It is not surprising that hardly any mammalian fossils are known from the Anglian glaciation, for at its severest the southern part of the country, the only part that was not covered by the deep ice sheet, was an arctic desert. The few that have been found are assigned to the early or late parts of the stage when glaciation was developing or retreating – a ground squirrel to the former and the red deer to the latter. As, furthermore, no vertebrate fossils of other classes are known from the Anglian the conclusion that the glaciation exterminated the entire mammalian fauna is inescapable. The deposits of the Anglian stage are a complicated series of tills, including the Boulder Clay, produced by the ice moving in different directions at different times as the glaciation proceeded.
When the ice at last retreated the temperate flora and fauna of the Hoxnian stage gradually moved in from the continent as the desert gave way to tundra, then to boreal forest followed by mixed oak forest. The fossils of this interglacial stage are preserved mainly in freshwater deposits, though some marine and estuarine deposits exist from its later part. It was during this stage, too, that man first made his way into the British Isles, for his palaeolithic flint artifacts have been found in several places. The former claim that man had been present at a much earlier time is now discredited – the ‘eoliths’ from the Crag that were supposed to be primitive tools are no more than fortuitously broken stones. The only skeletal remains of alleged palaeolithic man living in the Hoxnian stage that have been found in the British Isles are some fragments of a skull from the Thames terrace gravel at Swanscombe, Kent. One bit of the skull was found in 1935, another in 1936, and a third in 1955. Although Oakley in 1969
tabulated the Swanscombe skull, among the ‘early Neanderthaloids’ dating from about a quarter of a million years ago, the fragments, the occipital and two parietal bones, are indistinguishable from those of modern man. Since then there has been some controversy about the dating of the Hoxnian interglacial
’
; but a dating of material from ‘a few centimetres below’ the horizon of the Swanscombe skull gave ages of up to more than 272,000 years.
This, unfortunately, does not give irrefutable proof of the age of the skull, and still leaves open the possibility advocated by some that the skull fragments may have become included in the gravel as intrusions at a later date. With the possible exception of the Swanscombe skull, the earliest remains of man in the British Isles, apart from his artifacts, date from the middle of the Devensian glaciation, at least some two hundred thousand years later.
The Hoxnian mammalian fauna that moved in from the continent differed from that of the Cromerian, although many species were the same, or similar, such as the beaver, some voles, the wolf, marten, lion, boar, the straight-tusked elephant Palaeoloxodon antiquus, and the red, fallow, and roe deer. New arrivals included the arctic lemming, several voles, the cave bear, two species of rhinoceros replacing Diceros etruscus, Megaceros giganteus replacing several other species of giant deer, and the aurochs. Those that did not return, or were by then extinct, included the vole genus Mimomys, the sabre-tooth, the southern elephant, etruscuan rhinoceros, hippopotamus, zebrine horses, several species of deer, giant deer, and elks, the bison and musk ox.
When the climate became colder with the onset of the Wolstonian glaciation which reached its peak about 140,000 years ago, the fauna became more typically arctic, and those parts of the country not covered with ice were inhabited by hamsters, the arctic, Norway and steppe lemmings, the woolly mammoth, Mammuthus primigeneus, the woolly rhinoceros, Coelodonta antiquitatis, and the reindeer Rangifer tarandus.
At the end of the Wolstonian stage, about 120,000 years ago, the temperate Ipswichian interglacial stage began and lasted about 50,000 years. The climate and flora followed the usual sequence of an interglacial stage, the temperature reaching a peak higher, however, than that of the present day, and the flora progressing from arctic tundra to boreal forest, mixed oak forest and then regressing by similar steps to the onset of the next glaciation. Mammalian remains of the Ipswichian occur in river and lake gravels, muds, and brick earths, and in the deposits of some caves. Many of the mammals are species that form part of our present day fauna, and include the bank, water and field voles, the wood mouse, the red fox, badger, and wild cat, the red, fallow and roe deer; and some extinct only in historic times such as the beaver, wolf, brown bear, wild boar and aurochs. The cooler parts of the stage were also marked by the presence of ground squirrels, the woolly mammoth and the musk ox, whereas the warmer parts supported the spotted hyaena, the lion, the straight-tusked elephant, two kinds of rhinoceros, the giant deer, and the hippopotamus, the last indicating a comparatively high temperature as does the presence of the European pond-tortoise Emys orbicularis. Palaeolithic man, as shown solely by his artifacts, was present throughout the stage.
The following Devensian glaciation began about 70,000 years ago and lasted nearly sixty thousand years until it came to an end rather quickly about 10,000 years ago. It was the least severe of the three great glaciations as it left southern England and the midlands free of ice and thus a possible habitat for many species that can withstand a cold climate. During this stage the sea fell some three hundred feet below its present level so that England was widely connected with the continent over the site of the southern part of the North Sea, and northern Ireland was narrowly connected with southern Scotland. Stuart
remarks that the vast majority of Pleistocene vertebrate remains found in the British Isles, excluding post-glacial material, is probably of Devensian age. Most of the remains are found in river gravels and caves, some of the later ones in lake sediments. The flora of the ice-free regions was mostly tundra or open grassland, with some patches of boreal forest during short interstadial recessions of glaciation.
The fauna is typical of cold regions, though it includes some species of our present fauna such as the common shrew, the bank, water and field voles, the mountain hare, the fox, stoat, polecat, and red deer. Some of the species are not now associated with severely cold climates but nevertheless can withstand more cold than might be supposed; these are the leopard, lion, and spotted hyaena. On the other hand there are many species typical of colder habitats: a pika Ochotona, ground squirrel, the arctic lemming, several voles including the northern and tundra voles Microtus oeconomus and M. gregalis, the arctic fox Alopex, polar bear, glutton, woolly mammoth which became extinct at the peak of the glaciation about 18,000 years ago, woolly rhinoceros, reindeer, and musk ox. Several other large mammals left abundant remains in gravel and cave deposits; they include the wolf, the brown and cave bears Ursus arctos and U. spelaeus, a sabre-tooth Homotherium, the horse, giant deer, elk, a bison Bison priscus, and the aurochs.
Man returned after the peak of the Devensian glaciation as shown by his artifacts and by a few skeletal remains.
Some human teeth of middle Devensian age from Picken’s Hole cave in Somerset are the earliest human remains known in the British Isles apart from the Swanscombe skull whose alleged age has been challenged by some people. The largest find of palaeolithic man belongs to the late Devensian deposits of Aveline’s Hole in the Mendip Hills of Somerset, where bones representing thirty-one skeletons were excavated.
As the ice melted during the late glacial stage of the Devensian the climate became milder and reached a peak after about a thousand years in the Allerød interstadial or ‘amelioration’ as it is sometimes called, though amelioration could have a different meaning for a reindeer than for a red deer. Thereafter the climate again became colder until about 10,000 years ago when the ice finally disappeared inaugurating the Flandrian interglacial which has lasted until the present. By the end of the late glacial many of the large mammals had become extinct, although there appears to be no reason why they should not have survived into the Flandrian. Perhaps the change of climate and the resulting changes in vegetation deprived them of their ecological niches, but it is also possible that improved hunting skills of upper palaeolithic man may have overcropped and thus exterminated them. The few species not part of our present mammalian fauna that survived from the late glacial disappeared in the early part of the Flandrian, which is discussed in the next chapter.
CHAPTER 3 (#ulink_ea1453db-fb36-58b8-82a6-6bd629377c6b)
THE EVOLUTION OF THE ENVIRONMENT (#ulink_ea1453db-fb36-58b8-82a6-6bd629377c6b)
AT the beginning of the Flandrian stage, when the glaciation started to recede, the climate became warmer and thereafter varied between warmer and cooler so that it is convenient to subdivide the stage according to the prevailing climate of the time. In the first, Preboreal, phase the frost tundra of the country south of the ice began to be covered with growths of the dwarf or arctic birch, a shrub with stems and branches generally spreading over the ground and making a bush only a couple of feet or so high in sheltered places; it is a characteristic plant of the arctic and high mountains. It was followed by the tree birches spreading to make a forest so that in the following Boreal phase, when they were joined by pine and hazel, the forest cover was complete. During the Boreal phase the melting of the ice brought a rapid rise in the level of the sea which finally cut through the Strait of Dover about 7,000 years ago, whereas the southern part of the North Sea and eastern end of the English Channel had been dry at the beginning of the Pre-boreal. At the same time the climate became several degrees warmer than at present, producing the Atlantic phase, during which the forest cover was enriched by the addition of oak, and alder. Thereafter the climate became cooler about 4,500 years ago, introducing the Sub-boreal phase, and the forest was further enriched by ash, elm and lime. A minor rise in sea level marked the end of the Sub-boreal phase about 2,250 years ago, and the climate entered the Sub-atlantic phase that we endure at the present day.
At about the end of the Devensian glaciation the upper palaeolithic culture that man had evolved through many grades during the middle Pleistocene, was succeeded by the mesolithic culture characterised by the small flint artifacts called ‘microliths’. Of the several known mesolithic occupational sites, that at Starr Carr near Scarborough in Yorkshire has been meticulously excavated by Professor J. Clark and his colleagues, who have been able to draw a picture of the life of the inhabitants, and of the fauna and flora.
The site was occupied about 9,500 years ago as a winter hunting camp by three or four families of nomadic people; the settlement lay at the edge of a lake in the Vale of Pickering, with closed birch forest on the hill rising behind and willows along the reedy shore. The people lived on a platform of birch brushwood and were occupied not only in hunting and gathering roots of reeds and bog-bean, but also in knapping flint to make tools, some of which were used for making barbed spearheads from slivers cut from the antlers of red deer. The bones and antlers they left on the site show that they lived mostly on the flesh of red deer, but that they also killed roe deer, elk, aurochs and wild boar in lesser numbers. They had no domestic animals, and did not cultivate any crops. The remains of other mammals show that the fauna included the pine marten, fox, wolf, badger, hedgehog, hare and beaver.
Fig. 5. The Flandrian succession in the British Isles after the ice of the Devensian glaciation melted.
This late Pre-boreal fauna shows that forest animals, the deer and aurochs, had replaced the tundra-living mammals such as the reindeer, bison and wild horse while the birch forest increased with the rise in temperature. Until the rise in sea level at the end of the Preboreal phase, although Ireland had long been separated from Great Britain, the site of the southern part of the North Sea was dry land with the coast line extending from Flamborough Head to Jutland with a northern loop including the Dogger Bank. At the same time the English Channel extended no further east than Beachy Head.
The mesolithic people remained in occupation for over five thousand years, during which the sea level rose and cut off the British Isles from the continent. About 4,500 years ago the neolithic people arrived, migrating across the sea from the east, and soon completely replaced the mesolithic culture with their own. Throughout the many hundreds of thousands of years of the preceding part of the Pleistocene the palaeolithic and later the mesolithic people were no more than part of the fauna, and produced no appreciable alteration in the environment. They were plant gatherers and hunters and, though they may have contributed towards the extinction of some of the large mammals such as the mammoth, their influence on the composition of the fauna was in general negligible. They probably had to work hard to earn their living in the British Isles, but further south on the continent, where the climate was milder and food abundant, they appear to have satisfied their wants more easily so that they had enough leisure to make paintings on the walls of caves, to make sculptures and carvings, and to engrave stones and bone artifacts with abstract and representational designs.
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- Жанр: Зарубежные любовные романы, Природа и животные, Современная зарубежная литература
- Язык: Книги на английском языке
- Объём: 340 стр. 47 иллюстраций
- ISBN: 9780007406562
- Дата выхода книги: 30 сентября 2019
- Версия: 📚 Электронная книга
Mammals in the British Isles looks at the influences on their numbers and distribution, both now and in the past, examines aspects of their biology with emphasis on function and physiology, and concludes with an account of relationships with man.This book by Dr Harrison Matthews will be warmly welcomed by all those for whom his British Mammals, in this series, was a standard work for nearly 30 years. In recent years our understanding of the British species has expanded greatly. This volume offers a synthesis of modern knowledge derived from living animals studied in the field and covering all facets of mammalian life in the British Isles. It will be as important to a new generation of naturalists as the previous book was to an older one.The book is full of fascinating detail – of the shrews which scream in defence of territory to avoid fighting; of young rats that play to learn while adult otters play for fun; of vole 'plague' populations which crash as a result of stress; of monogamy and parental care of the dog fox – but it also paints a broader picture of interdependence, conservation and the part played by man.As much a part of nature as any other member of the fauna, it is man who has created the character of the environment – by clearing, draining, building and developing agriculture – and made available the wide variety of habitats occupied by indigenous, introduced and feral populations.Dr Harrison Matthews gives a general account of British mammals and the things influencing their numbers and distribution both now and in the past, examines aspects of their biology with emphasis on function and physiology, and concludes with an account of relationships with man and the measures he has taken for their control and conservation.
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