aye-aye
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. |
