The aye-aye (Daubentonia madagascariensis) is a rare tree-dwelling animal that is found only at a few localities along the eastern half of Madagascar, off eastern Africa. It is a member of a group of primitive primates known as Prosimians, most of which are lemurs. The aye-aye is the only surviving member of the family Daubentoniidae; a slightly larger relative (D. robusta) became extinct about 1,000 years ago.
Only a handful of aye-ayes survive in the wild, and it is a critically endangered species. It has suffered from extensive loss of its natural habitat of humid tropical forest, which now exists only in fragmented remnants, including 16 protected areas. The aye-aye is also killed by local people, who believe that it is an evil omen.
Because of its strange appearance and behavior, the aye-aye is sometimes referred to as the most bizarre of all primates. When it was first encountered by Europeans, it was incorrectly classified as a rodent. This was because of its large ears, squirrel-like bushy tail, and large, continuously growing incisor teeth. This primate has large eyes set in a cat-like face, which give it good night vision, and dark brown to black fur with long guard-hairs. Adults are approximately 3.3 ft (1 m) long and weigh up to 6.5 lb (3 kg).
The aye-aye's digits end in claws, except for the big toe and thumb, which have flat nails. The middle finger of each hand is extremely long and thin, and has a long claw that is used to dig insect larvae out of tree bark and crevices. When an aye-aye hears the movement of a beetle larva under the bark of a tree, it gnaws through the wood to uncover the tunnel of the grub, and then inserts its long finger to catch it. Research indicates that by tapping a branch, aye-ayes can locate grubs using a sort of echolocation. Aye-ayes also eat fruit, bamboo shoots, and free-ranging insects.
Aye-ayes forage at night, mostly in trees. They sleep during the day in a globe-shaped nest woven of leaves and twigs. They may spend several days in one nest before moving on to another. Several animals may share the same home range, but they are solitary animals, except for mothers with young. They have lived for as long 26 years in captivity.
The nocturnal habits of aye-ayes make it difficult to observe them in the wild, so little is known about their breeding and behavior. They are thought to breed every two or three years. A single infant is born after a gestation period of about 158 days (according to observations in captivity). In April 1992, an aye-aye named "Blue Devil" was born at Duke University's primate center (it was named after the university mascot). It was the first aye-aye born in captivity in the Western Hemisphere.