Due to its bizarre appearance and unusual feeding habits, it is considered by many to be the strangest primate in the world. It is the world’s largest nocturnal primate. Unusual physical characteristics include incisors that are continually growing (unique among primates), extremely large ears, and a middle finger which is skeletal in appearance, and is used by the animal as a primary sensory organ.
The aye-aye’s diet is very specialized, consisting mainly of the interior of Ramy nuts, nectar from the Traveller’s Palm tree, some fungi and insect grubs. The animals are also known to raid coconut plantations, and have been seen eating lychees and mangoes, which are also plantation crops. Most of what we know about the diet and social behavior of wild aye-aye populations is based on a two year study in the early nineties by Yale University Undergraduate, Eleanor Sterling.
Since a significant percentage of an aye-aye’s diet consists of insect larvae that dwell inside dead or living trees, the animals have evolved a specialized method for locating the larvae. As they walk along a branch, the animals continuously and rapidly tap it with their middle finger. Cupping their huge ears forward, the aye-aye listens intently to the echoing sounds coming from the tapped tree. When the sound indicates they are above an insect tunnel, the animals begin to tear off enormous chunks of the outer bark with their impressive teeth, until the insect tunnel is revealed. Then the aye-aye inserts its slender and highly flexible third finger into the hole, and when the prey is located, it is hooked with the tip of the finger and removed.
Aye-aye breeding can occur at any time of year. In April of 1992 an infant was born at the Duke Lemur Center whose mother was captured while pregnant. This was the first recorded captive birth of an aye-aye. In the wild, infants are weaned as early as 7 months, but they will continue nursing in captivity as long as they remain housed with their mothers– infants might still be nursing even at 1.5 years of age. In captivity, females give birth every 2 – 3 years. At the DLC, a captive born female bred at age 3.5 years, indicating that this is the age of sexual maturity in this species. Gestation period is around 170 days.
Of the sixteen captive births that have occurred at the DLC since 1992, four have occurred in October, two each in December, June, April, and January and one each in August, February, July and September.
Aye-ayes are nocturnal, solitary foragers who spend up to 80% of the night feeding and traveling through the forest canopy. The majority of their time is spent in the trees although traveling on the ground is reasonably common. Males have huge home ranges, between 100 and 200 ha, while the home ranges of females are much smaller, usually between 30 and 50ha. A male’s territory may overlap with that of several different males, and although encounters between neighboring males are rare, they might be hostile. Female ranges do not overlap with those of other females, but they always overlap that of at least one male. Aye-ayes sleep in elaborate tree nests during the day, with different animals possibly using the same nest on different days. Wild aye-ayes spend most of their lives alone. The only social interactions occur during courtship and when an infant is dependent on its mother. During these interactions, females are considered to be dominant over males, giving them preferential access to food. (Female dominance in primates is unique to prosimians.) In captivity, however, a male/female pair and their single infant might coexist peacefully for years.
Habitat & Conservation
Once considered one of the most endangered mammals in the world, the aye-aye has in recent years been shown to be much more widely distributed than originally thought. This is due to the fact that recent years have seen an influx of researchers into Madagascar, including those specifically looking for this rare and elusive animal. Current findings indicate that the aye-aye is sparsely distributed along the east coast and in the northwestern forests of Madagascar.
The main threats to the survival of the aye-aye are loss of habitat and hunting pressure. Unlike many lemur species that are hunted for food, aye-ayes are sometimes killed as crop-threatening pests in agricultural areas, and also because their bizarre appearance has traditionally led many villagers to regard the animal as an evil omen which must be killed on sight to avoid bringing bad luck onto an entire village. Aye-ayes are found in at least 16 protected areas, and several of these locations appear to have healthy populations of this lemur.
Worldwide, the captive population of aye-ayes stands at about 50. Thirty-three aye-ayes live in the United States, all managed by Duke, with 17 of those living on-site at DLC. Breeding has also occurred at the Jersey Wildlife Preservation Trust which holds 6 (4.2). In addition, the Bristol Zoo, London Zoo, Paris Zoo and Tokyo Zoo each holds one pair of aye-ayes.