This family contains a single species, the highly distinctive aye-aye. These animals are around 400 mm long excluding the bushy tail, which more than doubles the body length. The fur is long, woolly, and dark brown in color. The combination of bushy tail and woolly fur gives the animal a sort of unkempt, shaggy appearance. Aye-ayes have large, naked, mobile ears, a muzzle that is shorter than that of most lemurs but longer than lorises, and large eyes with yellowish brown irises.

The forefeet of aye-ayes are unique. All foretoes are long and thin, but the third is extraordinarily so due to an especially elongated metacarpal. It and all other toes except the hallux bear claws; the hallux has a nail.

Aye-ayes also have an unmistakeable skull and teeth. Unlike all other strepsirhines, they lack a toothcomb. The adult dental formula is 1/1, 0/0, 1/0, 3/3 = 18 (the deciduous dentition includes extra upper and lower incisors, premolars, and an upper canine). The adult incisors are tremendously enlarged and evergrowing. Only their anterior surface bears enamel, so they self-sharpen as they wear in the same manner as rodent incisors. Posterior to the incisors is a diastema. The cheekteeth are flattened and have indistinct cusps. The skulls are rounded and the facial region is reduced. An interparietal is present. The postorbital bar is complete, and the foramen magnum is shifted well beneath the skull. The bullae are large and enclose the tympanic ring. The dentary is also distinctively shaped, broad, with a relatively small coronoid process but a large articular process and condyle. The condyle is shifted ventrally relative to the dentary toothrow.

Aye-ayes eat insect larvae, which they retrieve from bark and wood by gnawing holes with their rodent-like incisors, then hooking the larvae out with their enlarged third forefingers. They locate wood-boring larvae by tapping on branches with the third finger and listening for movement. They also feed on fruit, eggs, and bamboo shoots.

These animals are quadrupedal. They do not use the "vertical clinging and leaping" style of locomotion common to many other strepsirhines. Little is known about their social behavior; aye-ayes are usually seen singly or in pairs. They occasionally emit brief cries but are usually silent.

The fossil record of aye-ayes extends to the Pleistocene.

Literature and references cited

Feldhamer, G. A., L. C. Drickamer, S. H. Vessey, and J. F. Merritt. 1999. Mammalogy. Adaptation, Diversity, and Ecology. WCB McGraw-Hill, Boston. xii+563pp.

Groves, C. P. 1989. A Theory of Human and Primate Evolution. Oxford Science Publications, Clarendon Press, Oxford. xii+375 pp.

Napier, J. R., and P. H. Napier. 1985. The Natural History of Primates. British Museum (Natural History), London. 200pp.

Nowak, R.M. and J.L. Paradiso. 1983. Walker's Mammals of the World, Fourth edition. John Hopkins University Press, Baltimore, London.

Szalay, F. S., and E. Dodson. 1979. Evolutionary History of the Primates. Academic Press, New York. xiv+580 pp.

Thorington, R. W., Jr., and S. Anderson. 1984. Primates. Pp. 187-216 in Anderson, S. and J. K. Jones, Jr. (eds). Orders and Families of Recent Mammals of the World. John Wiley and Sons, N.Y. xii+686 pp.

Vaughan, T. A. 1986. Mammalogy. 3rd Edition. Saunders College Publishing.vii+576 pp.

Vaughan, T. A., J. M. Ryan, N. J. Czaplewski. 2000. Mammalogy. Fourth Edition. Saunders College Publishing, Philadelphia. vii+565pp.

Wilson, D. E., and D. M. Reeder. 1993. Mammal Species of the World, A Taxonomic and Geographic Reference. 2nd edition. Smithsonian Institution Press, Washington. xviii+1206 pp.


Phil Myers (author), Museum of Zoology, University of Michigan-Ann Arbor.


bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.


uses smells or other chemicals to communicate


animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.


having the capacity to move from one place to another.


reproduction that includes combining the genetic contribution of two individuals, a male and a female


uses touch to communicate