The fingers are long and narrow, the third finger extremely so. The thumb is flexible but not truly opposable, though the first toe is opposable. All the digits have pointed, clawlike nails, except the first toe, which has a flat nail. Females have two mammae located abdominally, and males have a penis bone. The incisors are large, curved, and similar to those in rodents, i.e., chisel-like, with enamel on only the front surface, and ever growing.
Canines are absent in the permanent dentition but present in the deciduous dentition.
In the adult aye-aye there is a large space between the incisors and the premolars. The modified cheek teeth have flattened crowns with indistinct cusps. The modern aye-aye lives in forests, mangroves, and bamboo thickets. It is arboreal and nocturnal. During the day it sleeps in a nest constructed amidst dense foliage in a strong fork of a large tree, about 10-15 meters above the ground.