The Zoologist/4th series, vol 5 (1901)/Issue 721/Notes on the Sciuridæ, Bonhote
No. 721.—July, 1901.
NOTES ON THE SCIURIDÆ.
By J.L. Bonhote, M.A., F.Z.S.
In a civilized and thickly populated country, the first of the wild native fauna to fall before the superior advance of man are the larger mammals; and, although in many cases man has been the loser by the wantonness of his slaughter, yet as a rule, such destruction having been for the general benefit of the human race, one has perforce to lay aside one's sentimental desires and accept the inevitable. Among the smaller mammals, however, no such tale of slaughter exists, and Rats and Mice maintain their existence under the very roofs of man, who is practically powerless to diminish their numbers. That the abundance of these latter is in part due to the scarcity of the larger mammals is to a great extent true; but as my object is not to discuss the protection or otherwise of mammals, let us turn to the one group which does comparatively little harm, and to the species which, although of diurnal and conspicuous habits, still remains in numbers to enliven our woods and forests—the Squirrel (Sciurus vulgaris).
The Squirrel, as most people know, is a rodent of arboreal habits; in shape and size it much resembles a Rat, but its feet are longer and more plastic, enabling it to grasp with greater ease the trees on which it lives. The front feet have only four toes, the thumb being a mere stump, which is much used for holding the nuts while they are being cracked. The tail, which is large and bushy, serves the double purpose of balancing the body whilst leaping through the air, keeping it dry by being folded over its back, and enabling the animal to keep warm when curled around it.
Squirrels are widely dispersed throughout the world, being absent alone from Australia and Madagascar. In the Palæarctic Region, which stretches from England to Japan, only one species is known, although individuals from various localities are constant to themselves, and slightly different from their neighbours. It is, however, in the Indian and Oriental region that the species reaches its maximum development, and the number of species recorded from that region is very large. Putting aside for the moment the question of species, subspecies, races, varieties, &c., and looking as far as possible at the groups as a whole, we find that they give us such abundant opportunities for the study of colour in nature, and the causes by which it is influenced, that they can but form a valuable lesson to the zoologist, whatever may be his particular line.
I will preface my remarks by saying at the outset that our knowledge on the subject is very limited, and that at present we are in the position of only recording facts, which, however, may at some future time bear considerable fruit. In the first place, there is the colour of the animals, which, in the case of our English Squirrel, may be roughly called red. This colour is modified during the course of the year by two moults, in spring and autumn, the change taking place in May and October. In its winter dress it is greyish brown in colour, the hairs being long and soft, the tail is of a similar colour, and the ears are also clothed with long brown hairs; in May all the body-hairs are cast, and are replaced by shorter and coarser hairs of a much redder colour, while the tufts on the ears are not replaced. The hairs of the tail are not moulted at the spring moult. This may seem to be only the natural course of things to an ornithologist, but a moment's thought will at once show us that the causes must be very different. The tail as a balancer must be as much required in summer as in winter, if not more so; but, on the other hand, the tail as a warm covering is not so necessary, and hence probably the reason of its not being renewed. There is, however, a further noticeable point about this tail, which is fully dealt with by Mr. Thomas in the article quoted above, and that is, that as it gets older it becomes lighter in colour, till by autumn it is nearly white. Mr. Thomas further points out that the red hairs of summer show no tendency to this bleaching process, whilst the brown winter hairs slowly bleach throughout the time they are worn, but, being replaced in spring, the process is never so conspicuous on the body as on the tail, where the change goes on throughout the year.
Although we are accustomed to see fur and feathers of all kinds "bleach" under the action of light, we are perhaps too much inclined to take it for granted that the bleaching action on a living animal goes on by the same process. This may be true of a bird's feather, which is considered histologically dead, yet it is hardly conceivable in a mammalian hair, which maintains throughout its life an active connection with the body; and, bearing this in mind, one may notice that the bleaching, which, if the tail were dead, one would expect to go on uniformly, starts at the tip, and gradually spreads downwards towards its base, thereby, to my mind, clearly showing that, although this lightening may, and probably does, take place by a merely mechanical process, yet such a process cannot act on the normal living hair. I may be perhaps allowed to mention on this matter, that when bleaching goes on among birds that bleaching process does not begin and continue slowly throughout the life of any particular feather, but a feather which may show hardly any change during the first six months of its life will suddenly undergo considerable disintegration and bleaching on the seventh. Does it not seem as though vital forces existed in that feather during the earlier part of its life? Taking our remarks on bleaching into a rather wider field, we find that this "fading" is restricted either to certain races, or to certain parts of the animals—for instance, among the large and closely allied Squirrels of the Ratufa bicolor group, as I have already shown in a previous paper, which inhabit the Malay Peninsula and Borneo. This bleaching is entirely absent in a large form (R. gigantea), while being present and a very conspicuous feature in the very closely allied form (R. bicolor), although chiefly confined to the body.
In R. affinis (another species) it is general and uniform both on the body and the limbs, and in R. ephippium is almost entirely absent, or, if present, confined, as in the case of the European Squirrel, to the tail only.
To account for changes of this kind as being due merely to the bleaching or wearing of the hairs seems to me hardly a sufficient explanation, for if that were the sole cause there would be no reason why one portion of the animal should bleach more than another. It might be accounted for in some cases, as Mr. Thomas has pointed out in our European Squirrel, by the absence of a moult; but such a solution would hardly hold good in the case of R. bicolor, where the line of demarcation is irregular, and varies in individuals; or again, in the case of R. affinis, where the bleaching, which is general, follows so quickly on the growth of the new pelage that hardly any specimens in unbleached pelage are known in our museums.
It seems to me that the only way to account for these phenomena is to suppose that these hairs must sever their physiological connection with the body, and that, when disconnected, the destructive action of light and weather is able to act; but to thoroughly elucidate this matter microscopical examination of fresh specimens is necessary. My object in this paper is merely to draw attention to the facts.
Apart from this seasonal change by bleaching, there are two other forms of seasonal pelages to be observed. The one, which may be noticed on S. berdinoni, and doubtless many other forms, in which the pelage worn in summer is a much brighter and more intense edition of that worn during the colder portions of the year. Whether the change takes place by abrasion or by moult, I am unable to say—possibly the former, as the dark lateral stripes can be clearly distinguished in the winter pelage, but very much concealed owing to each hair having a dark brown tip. The other seasonal pelage is that in which the brightest phase takes place in winter, and, instead of being a brighter edition of the duller pelage, is markedly distinct. The only two examples of this pelage with which I am acquainted are Sciurus caniceps and S. atrodorsalis. During the greater part of the year these forms wear a dull grey dress, but in the winter months (from December to February) both sexes assume on the back, by moult, a much more brilliant pelage, which in the case of the former is deep orange, and in the case of the latter a glossy black. It is supposed that the assumption of this dress coincides with the pairing season, but I am not aware that this has been actually proved.
Let us now turn again to our European Squirrel. Many depredations on young trees and birds are laid to his account, and I fear it must be acknowledged these accusations are to some extent true. He is in the main, however, a vegetable feeder, living chiefly on beech-mast and acorns, but little in the way of seeds comes amiss to him; and when in the fir-woods the cones are found very much gnawed by his strong and sharp teeth. With one I had in captivity, whose chief food used to be hazel-nuts, the method of eating them was always the same. The nut would be held by the large end, so that the long axis of the narrow portion was transverse to the mouth, when an incision would be made until there was a hole large enough for the insertion of the incisors between the shell and kernel. Into this hole the lower incisors would be placed, and a piece of the shell broken off by a sharp twist of the head; similar actions would be repeated until the whole of the shell was broken off, and then the kernel would be devoured.
Although, as I have said, their food is chiefly, if not entirely, vegetable, my tame one would frequently use his teeth on the furniture, boots, or anything handy, apparently from mere wanton destruction, and when offered fresh twigs with any bark on would invariably strip them of the bark, although it did not appear to be eaten.
In England pairing takes place early in April, and the young are born about midsummer in large nests or "dreys," composed of sticks, on which is collected a large mass of moss neatly hollowed out inside, the opening lying to the side. Several of these "dreys" are said to be built by each pair, and if the young be discovered they are moved as soon as possible to another nest. The male Squirrel remains with the female most of the summer, and in the autumn family parties may still be seen together.
To see a party of Squirrels at play is a sight which no one can fail to appreciate; their actions are so full of life and activity, running up one tree, jumping to the next, sliding to the ground, a few yards run and up another tree, evidently in full enjoyment of their own powers and activity. Such a sight is still to be seen in any of our woods, and it is still to be hoped may long remain so, safe from the weapons of the casual loafer, or still more dangerous keeper.
- For actual descriptious of various European forms, see G.E.H. Barrett-Hamilton, P.Z.S., 1899, p. 3.
- See O. Thomas, Zool. 1896, p. 401.
- Ann. and Mag. Nat. Hist. ser. vii. vol. v. p. 490 (1900).
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