But in 1859 Dr. H. Sandwith, the Colonial Secretary from England to the Mauritius, wrote to Professor Owen that he had secured a fine, healthy adult male Aye Aye from Madagascar, which, after having once escaped and been recaptured, was put into spirit and sent to England. This specimen formed the subject of a most complete and suggestive work of the learned Professor. But a long communication from Dr. Sandwith himself is printed in the Society’s Proceedings for 1859, and some observations upon the habits of a female Aye Aye which reached the Society’s collection in August, 1862, are printed in the Society’s Proceedings for that year, and in the Annals of Natural History, vol. xii.
From these various sources we learn the following as to the Aye Aye’s mode of life:—
During the day the Aye Aye sleeps; it then lies upon one side, with the body curved and nearly covered by the great bushy tail. It is sensitive to cold, and sometimes covers itself with a piece of flannel, even in warm weather.
At dusk it awakes and climbs about, securely grasping the branches with its prehensile feet, and often hanging suspended by them, and using its fingers as a comb for its long tail. In this operation the middle digit is especially serviceable, and it is also used in clearing dust from its face and other parts, the other digits being then often partially closed. It was found that the captive Aye Aye in the Zoological Gardens used only the left hand in feeding from a dish, although the right seemed equally at its command.
The fourth digit (annularis), which is the longest and largest, is thrust forward into the food, the slender medius raised upward and backward above the rest, while the pollex is lowered so as to be seen below and behind the chin. In this position (an almost impossible one, by the way, for men or monkeys) the hand is drawn backward and forward rapidly, the inner side of the finger passing between the lips, the head of the animal being held sideways, thus depositing the food in the mouth at each movement; the tongue, jaws, and lips are kept in full motion all the time. Sometimes the animal will lap from the dish like a cat, but this is unusual. During all the hours in which the Superintendent of the Gardens watched it, no sound was made, nor was there any manifestation of anger or shyness.
This specimen seemed to care nothing for insects, but fed freely upon a mixture of milk, honey, eggs, and such sweet and glutinous things, and the observer concluded, therefore, that its natural food is rather fruit than insects; but this only indicated that the Aye Aye did not like British meal-worms, grasshoppers, wasp-larvæ, and the like, and no more proved that it was not insectivorous than a man’s refusal to eat turnips would show that he cared nothing for potatoes. And surely nothing can be more conclusive than the following account which Dr. Sandwith gives of the proceedings of his specimen:—
“I found he would eat bananas and dates; and he drank by dipping a finger into the water and drawing it through his mouth so rapidly that the water seemed to flow in a stream; after a while he lapped like a cat, but the former was the more usual method, and seemed to be his way of reaching water in the clefts of the trees.
“I happened to put into his cage some thick sticks, which were bored in all directions by a large and destructive grub called the ‘Moutouk.’ Just at sunset the Aye Aye crept from under his blanket, yawned, stretched, and betook himself to his tree, where his movements are lively and graceful, though by no means so quick as those of a squirrel. Presently he came to one of the worm-eaten branches, which he began to examine most attentively; and, bending forward his ears and applying his nose close to the bark, he rapidly tapped the surface with the curious middle digit, as a woodpecker taps a tree, though with much less noise, from time to time inserting the end of the slender finger into the wormholes, as a surgeon would a probe. At length he came to a part of the branch which evidently gave out an interesting sound, for he began to tear it with his strong teeth; he rapidly stripped off the bark, cut into the wood, and exposed the nest of a grub, which he daintily picked out of its bed with the slender, tapering finger, and conveyed to his mouth.”
This medius, then, can be used in turn as a pleximeter, a probe, and a scoop; and not the least remarkable circumstance is the coincidence between the diameter of the hole made in the wood by the incisor teeth and the width of this digit; for although we cannot say that the size and power of the head are such as to limit the width of the teeth, yet, granting that their size is so limited, it is evident that none of the ordinary digits would be of the least service as an instrument of either discovery or extraction; and whatever view we may adopt as to the means by which these structures were produced, we must surely, with the great anatomist, recognise not only “the direct adaptation of instruments to functions, of feet to grasp, of teeth to erode, of a digit to feel and to extract, but we discern a correlation of these several modifications with each other, and with modifications of the nervous system and sense-organs—of eyes to catch the least glimmer of light, and of ears to detect the feeblest grating of sound—the whole forming a compound mechanism to the perfect performance of a particular kind of work.” The Aye Aye obviously belongs to the branch of Vertebrates and the class of Mammalia; but some zoologists have placed it with the squirrels in the order Rodentia, and others with the Lemurs, in the order Quadrumana or Cheiropoda; there is also a certain superficial resemblance to a cat; but the real issue has been between those who follow Buffon and Cuvier in giving prominence to the ever-growing incisor teeth, which agree with those of the rodents, and those who, like Schreber and De Blainville, regard the limbs as of more importance, and point out their resemblance to those of monkeys.
It is now generally conceded that Professor Owen’s researches have decided the question in favour of the latter view, for he shows that the only rodent features are the teeth, and similar ever-growing incisors are found in at least one other mammal, the marsupial wombat, which no one has thought of calling a rodent: on the contrary, the hair, the tail, the form of the head and body, the length of the intestines, the heart and blood-vessels, the brain, and the limbs tend to separate the Aye Aye from the rodents, and to join it with the Cheiropoda; and although the extraordinary middle digit has no fellow in the whole animal kingdom, yet this modification of the terminal segment of a limb is another link between the Aye Aye and that lowest family of the Cheiropoda, the Lemuridæ, which, like it, are mostly natives of Madagascar, and, besides being nocturnal in their habits, whence the name Lemures (ghosts), are also distinguished from all other mammals and from each other by peculiar, and, at present, unaccountable modifications of the fingers and the toes. In one species the forefinger is as if amputated; in another a single toe bears a claw, while the others bear nails; and in a third, two toes are thus provided with claws.