Due to its bizarre appearance and unusual feeding habits, the aye-aye 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.
Additional information about the DLC’s aye-ayes — from our first imports to the present — can be found in our WINTER 2017 newsletter, devoted exclusively to these rare and amazing lemurs. Our newest infant, Agatha, is the subject of the article “Rare aye-aye born at the Duke Lemur Center,” published September 21, 2017. See video footage, too, of month-old Agatha during her routine weigh-ins.
The aye-aye’s diet is highly 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.
HERE is a video of two aye-ayes, Ardrey and her daughter Elphaba, using the same process to eat eggs as they would to locate and eat insect larvae that dwell inside trees. First they tap, then they chew, and finally they use their long flexible middle fingers to dip into and remove the yolks of the eggs. When they finish, the delicate eggshells remain fully intact, except for the small hole created by the aye-ayes’ strong front teeth!
Click HERE to see Agatha, a five-month-old infant aye-aye, learning how to tap-forage from her mom, Medusa.
Video: Aye-Aye Tap-Foraging at the DLC
HERE is another video: Watch two aye-ayes, Ardrey and her daughter Elphaba, using the same process to eat eggs as they would to locate and eat insect larvae that dwell inside trees. First they tap, then they chew, and finally they use their long flexible middle fingers to dip into and remove the yolks of the eggs. When they finish, the delicate eggshells remain fully intact, except for the small hole created by the aye-ayes’ strong front teeth!
Aye-aye breeding can occur at any time of year. In April of 1992 an infant, Blue Devil, was born at the Duke Lemur Center whose mother, Endora, was captured in Madagascar while pregnant. This was the first recorded captive birth of an aye-aye. Angelique, born at Duke in 2005, was the first aye-aye ever born to parents who themselves were born in captivity. Merlin, “who as clueless and knew nothing about breeding,” had to be coached for two years by Duke staff before breeding successfully with Ardrey to produce Angelique. The experience “taught the center’s primatologists an invaluable lesson — that the complex creatures need socialization to mate.” (See “Angelique the Aye-Aye, A Primate Center Triumph,” published in Duke Today in 2006.)
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. Learn more about Ardrey’s pregnancy with Elphaba in Jason Bittel’s “What I learned from hanging out with lemurs” (2014).
Of the 16 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.
When aye-ayes get excited or agitated, their long, mostly white guard hairs stand on end and give the poofed-up lemur the appearance of an animal twice its actual size! This adaptation perhaps evolved as a strategy to make the aye-aye look more threatening to would-be predators, but it can also be seen at times when the animal is not being threatened. For example, our techs have reported seeing it during play behavior between a mom and an infant or juvenile, and it can also be observed in instances similar to those of Grendel (pictured below): he just got moved to a brand new room and, although the size and shape of the new room were exactly the same as the old, the layout of branches and many of the smells were totally different. At first Grendel just wasn't sure what to make of it.
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. As of December 2016, there were 23 captive aye-ayes in the United States: 10 males and 13 females. Of these, nine reside at the Duke Lemur Center and 14 are held at six additional AZA institutions. All but one of these 23 are descendants of the DLC’s original eight wild caught founder animals. An aye-aye pedigree chart can be viewed HERE.
Aye-aye breeding has also occurred at the Durrell Wildlife Park (Jersey Islands). Overseas, the Bristol Zoo, London Zoo, Paris Zoo, Tokyo Zoo, and Frankfurt Zoo house aye-ayes that descend from the DLC’s founding eight.
How You Can Help
Adopt an aye-aye: Want to learn more about aye-ayes AND help support their care, not only here but in Madagascar? Consider symbolically adopting Agatha, a young female aye-aye, through the DLC's Adopt-A-Lemur program! Adoption packages start at just $50 -- see below for options.
Send an aye-aye a present: You can send special treats like coconuts to the DLC's aye-ayes, as well as raw materials for us to construct special enrichment activities to keep them happy and healthy. Simply visit our amazon wishlist! Aye-ayes in particular love coconuts, coconut milk, peanut butter, and any of the fun treats labelled "aye-aye enrichment item."
Spread the word: This spring, 7-year-old Hailey wrote to us asking if we’d consider posting her best drawing of an aye-aye – her favorite animal in the world – so others could learn more about these amazing lemurs and why it’s important for us to save them.
Thank you so much, Hailey, for helping the DLC save lemurs! Your love for aye-ayes and your desire to teach people about them is inspiring, and it means so much to us. You’ve already made a positive difference, and you’re just getting started!