Collins New Naturalist Library. L. Matthews Harrison

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СКАЧАТЬ 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.³⁹

      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 1945.¹³¹ 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 СКАЧАТЬ