The aye-aye (¹/₉ nat. size)

An antique wood-engraved print of a pair of aye-ayes (Daubentonia madagascariensis), which appeared in The Royal Natural History, edited by Richard Lydekker.

• This engraving appeared in The Royal Natural History to illustrate the following article:
  
  The last of the lemur-like animals, and, at the same time, of the whole order of Primates, is the aye-aye of Madagascar, which has teeth so utterly different from all other members of the order that it was long considered to belong to the Rodent order (rats, rabbits, etc.).
  The most peculiar feature about the teeth of the fully adult aye-aye is that the front, or incisor teeth, are reduced to a single pair in each jaw, which are curved, and have their extremities brought to a sharp chisel-like edge, admirably adapted for gnawing and rasping hard substances. The structure of these teeth is in fact precisely the same as in the front teeth of rats and beavers; their sharp cutting-edge being produced by the circumstance that while the body of the tooth is formed of the comparatively soft ivory, the front surface is faced with a layer of hard flinty enamel. And it will be obvious that the result of wear in a tooth of this type will be to produce a chisel-like edge. It will further be apparent that such a tooth, if continually employed in rasping away hard substances, would be very quickly worn away altogether, if it were of the same length as ordinary teeth, and not provided with some kind of renewal. This difficulty is obviated by the front teeth of the aye-aye remaining open at their lower ends, and undergoing a continual process of growth; so that as their summits are worn away they are pushed further up from below. In all these points their teeth are precisely similar to those of the Rodent Mammals. A further resemblance to Rodents is shown by the absence of tusks in the aye-aye; and also by the cheek-teeth being separated by a long gap from the incisors, as well as by being reduced in number, and having their crowns with nearly flat surfaces, instead of being surmounted with the sharp cusps found in those of the true lemur. Indeed, the total number of teeth in the adult aye-aye is only eighteen; these being expressed by the formula i¹/₁, c⁰/₀, m³/₃, or exactly the same as in many Rodents.
  If, then, the teeth of the adult aye-aye are so exactly like those of a Rodent, the reader may well ask why it is not placed among the rats and beavers, instead of among the lemurs. To this it may be replied that in the young aye-aye the milk- or baby-teeth are very much more like those of the true lemurs; while the anatomy of the skeleton and the soft parts is essentially that of a lemur, and not that of a Rodent. The resemblance of the skull and teeth of the aye-aye to those of a Rodent, is, indeed, an excellent instance of what zoologists term an adaptive or parallel resemblance. When two animals belonging to totally different groups have more or less nearly similar habits, it frequently results that they will closely resemble one another in at least some part of their structure; such particular structure being the one best adapted for a particular mode of life. In all such cases a superficial examination of the animals in question will frequently lead to their being referred to one and the same group; while further minute investigations will reveal the fact that their deep-seated internal structure—which alone reveals their true affinities—is very different. Such was the case with the aye-aye, which was at first referred to the Rodents; its affinities to the lemurs not having been discovered till a fuller examination.
  The aye-aye agrees with the true lemurs in having the great toe of the foot furnished with a flattened nail, and capable of being opposed to the other toes; this feature being alone sufficient to prove that the creature has nothing to do with the Rodents. With the exception of this great toe, however, all the toes and fingers, which are very long and narrow, are furnished with narrow and sharply-pointed claws. Although both the hands and the feet are large in proportion to the size of the animal, yet the great peculiarity is concentrated in the hands, in which the fingers are much longer than are the toes of the feet. One finger—namely, that corresponding to our middle finger—is more remarkable than the others, being of great length and extreme slenderness. It is probable that this ghostly middle finger is employed in extracting from their burrows the larvae which, as we shall shortly learn, appear to form a portion of the creature's natural diet.
  In size the aye-aye may be compared to a cat; its total length being about 3 feet, of which the larger moiety is formed by the bushy tail. The comparison with a cat may be further extended to the short and rounded head and cat-like face of the animal. The rounded ears are, however, relatively larger than those of a cat, and have the peculiarity of being nearly naked. The fur is long, and composed of a mixture of longer stiffish hairs, with an under-coat of more bushy and shorter ones. The prevailing colour is dark brown, tending to black; the throat being yellowish-grey, and the under-parts showing a rufous tinge. Some of the longer hairs on the back are whitish, thus producing a somewhat mottled appearance in the fur.
  The aye-aye was discovered by the French traveller Sonnerat—who likewise first obtained the indri—as far back as the year 1780; and it was described in the first year of the present century by Baron Cuvier, who regarded it as a kind of squirrel. Nothing more was heard of the creature from Sonnerat's time till 1860, when specimens were sent to this country, and described by Sir Richard Owen. The following account of the habits of the aye-aye in its native land was published in 1882 by Mr. L. Baron, a missionary in Madagascar. "The aye-aye," writes Mr. Baron, "lives in the dense parts of the great forest that runs along the eastern border of the central plateau of the island, but only in that part of it which separates the Sihanaka province from that of the Betsimisaraka, and which is about twenty-five miles from the east coast, in latitude 17° 22" S., or thereabouts. Possibly there are other parts of the country where the aye-aye is found; but so far as my knowledge extends (and I have made inquiries in different parts of the island), this is the only region where the creature finds its home... From what I have gathered from the natives, it seems to be pretty common, its nocturnal habits, and the superstitious awe with which it is regarded (and of which I shall speak presently) accounting for its apparent rarity.
  "The native name of the animal is Haihay (Hihi); but this is not derived from the exclamations of surprise which the natives exhibited at the sight of an unknown animal, but is simply onomatopoetic, the creature's call being haihay, haihay. The animal, as is well known, is nocturnal in its habits, prowling about in pairs—male and female. It has but one young one at birth. It builds a nest about 2 feet in diameter, of twigs and dried leaves, in the dense foliage of the upper branches of trees. In this it spends the day in sleep. The nest is entered by a hole at the side. The teeth are used in scratching away the bark of trees in search of insects, and the long claw in digging out the prey when found. A white insect called Andraitra (possibly the larva of some beetle), seems to form its chief food. I was told that it frequently taps the bark with its fore-feet, and then listens for the movement of its prey beneath, thus saving itself useless labour. It does not flee at the sight of man, showing that for generations it has not been molested by him; which is indeed true, as the following will show. The natives have a superstitious fear of the creature, believing that it possesses some supernatural power by which it can destroy those who seek to capture it or to do it harm. The consequence of this is that it is with the greatest difficulty one can obtain a specimen. With most of the people no amount of money would be a sufficient inducement to go in pursuit of the creature, 'because,' say they, ' we value our own lives more than money.' It is only a few of the more daring spirits among them, who knowing the odiny, that is the secret by which they can disarm it of its dreaded power, have the courage to attempt its capture. Occasionally it is brought to Tamatave for sale, where it realises a good sum. Now and then it is accidentally caught in the traps which the natives set for lemurs; but the owner of the trap, unless one of those versed in the aye-aye mysteries, who know the charm by which to counteract its evil power, smears fat over it, thus securing its forgiveness and goodwill, and sets it free."
  Another account was published in the following year by the Rev. G. A. Shaw, also a resident in Madagascar, and since it differs somewhat from the preceding, which it supplements in some other respects, it may be likewise quoted. Mr. Shaw starts by stating, in opposition to Mr. Baron, that the name of the creature is derived from hay! hay! the Malagasy exclamation of surprise; the animal being known to the natives as the Haikay (pronounced Hayekaye). Be its origin what it may, there is thus full testimony that the name by which we know the creature is substantially the same as that by which it is known in its native land.
  "Being a nocturnal animal," Mr. Shaw continues, "it is very difficult to get any reliable information concerning its habits in the wild state, and native reports are altogether contradictory with respect to these matters. Even with reference to its natural food no satisfactory explanation can be obtained from the people. Many assert positively that it lives on honey; but one I had in captivity would not eat honey in any form, either strained or in the comb, or mixed with various things I thought he might have a fancy for. Others say it lives on fruits and leaves; others that birds and eggs are its natural food. I fancy from what I saw of my captive that both these conjectures are nearer the truth; for after a few days, during which it would eat nothing, and it was thought that the proper food had not been offered (but it was in reality pining or sulking), it took several fruits which I was able to procure for it. It liked bananas; but it made sorry efforts at eating them, its teeth being so placed that its mouth was clogged with them. The small fruits of various native shrubs it also devoured, as also rice boiled in milk and sweetened with sugar; but meat, larvae, moths, beetles, and eggs it would not touch. But I noticed that when I came near its cage with a light, it almost invariably started and went for a little distance in chase of the shadows of the pieces of bananas attached to the wirework in front of its cage; and I think that if I could have procured some small birds it would have, if not devoured them, at any rate killed them for their blood, as some lemurs are known to do. It drank water occasionally, but in such a way as to make it highly probable that it does not drink from streams or pools in the ordinary way. It did not hold its food in its hands as the lemurs which I have had in captivity have done, but merely used its hands to steady it on the bottom of the cage. But whenever it had eaten, although it did not always clean its hands, it invariably drew each of its long claws through its mouth, as though, in the natural state, these had taken a chief part in procuring its food.
  "In some accounts, given by different writers, the haikay is said to be easily tamed, and to be inoffensive. ... In each of these qualities, I have found, both from native accounts, and from the specimen I have kept, that exactly the reverse is the case. It is very savage, and, when attacking, strikes with its hands with anything but a slow movement. As might be imagined in a nocturnal animal, its movements in the daytime are slow and uncertain; and it may be said to be inoffensive then. When it bit at the wire-netting in the front of its cage, I noticed that each of the pair of incisors in either jaw could separate sufficiently to admit the thick wire even down to the gum, the tips of the teeth then standing a considerable distance apart, leading to the supposition that, by some arrangement of the sockets of the teeth, they could be moved so far without breaking. The haikay brings forth one at a birth, in which the long claw is fully developed."
  It has been observed that captive aye-ayes are very partial to the juice of the sugar-cane, which they obtain by ripping up the canes with their front teeth; and since sugar-cane grows wild in Madagascar, we may infer that its juice forms a part of the food of these animals in their wild state. It is, therefore, probable that the diet of the aye-aye is a mixed one, consisting partly of grubs, partly of the juices of plants, partly of fruit; but whether birds or their eggs also form a part of the bill of fare must be left for future observers to determine. The favourite haunts of these animals appear to be the bamboo-brakes, which form such a large portion of the forests in some regions of the island.

• Fauna > Madagascar > Mammals > Daubentonia madagascariensis