Aye-Aye, Daubentonia madagascariensis
AYE-AYE
Daubentonia madagascariensis
Geographic Distribution and Habitat
Aye-ayes, like all lemurs, are found on the island of Madagascar. They have been recorded along the western region and central to the eastern coast of this island nation. Despite their large geographical range, the aye-aye population density in these areas is surprisingly low, making them a rare and precious species that requires urgent conservation efforts.
They live in various forest types, including rainforests, scrub, mangroves, and plantations where they require high canopies (30-50 feet/10-15m) where they can build nests, and adequate hardwood trees that provide sufficient fruits and insects for food. Some aye-ayes live in or near plantations where they may subsist on coconuts.
Aye-ayes are genuinely one-of-a-kind. They are the only living members of their family, “Daubentoniidae.” Their unique appearance mistakenly led early explorers to classify these primates as rodents or kangaroos.
According to folklore, aye-ayes are considered evil because of their strange appearance. Locals, it is said, do not like finding or talking about them. Some researchers speculate that their common name, possibly derived from the local language word “heh-heh,” which means “I’m not sure,” may hold a deeper, more mysterious meaning, indicating the people’s reluctance to talk about them.
Size, Weight, and Lifespan
Aye-ayes are the largest nocturnal primates in the world, weighing between 5.5 and 6.2 pounds (2.5-2.8 kg). An average adult measures about 15 inches long (38 cm), and there is no sexual dimorphism, which means that the males and females look similar and are about the same size. Their tail is longer than their body, measuring 17-21 inches (44-53 cm), and they use it to balance themselves as they scamper along branches.
Their lifespan in the wild is unclear, but they can live in captivity for more than 20 years.
Appearance
“Bizarre!” is how most people describe the aye-aye’s appearance. They have short snouts, prominent pink noses (like possums), rat-like incisor teeth, large ears, and bushy squirrel-like tails. Their body is covered in dark hair, and their fluffy tails have long hairs measuring about 9 inches (22cm), one of the longest hair lengths found on primates. Their pelage (coat) has an outer layer of wiry white-tipped guard hairs. Guard hairs are coarse, longer hairs that protect aye-ayes from injuries as they climb through canopies. When aye-ayes become startled, they raise their guard hairs to make themselves look larger and more intimidating. This hair-raising, or piloerection, is a defense mechanism to fend off competitors or predators that might want to grapple with them.
Imagine you are in a dark forest and hear a tapping sound from the tree canopy. You look up to see an aye-aye with wide eyes and long bony fingers moving around in the canopy. It would undoubtedly frighten you! Unfortunately, people have misjudged the unusual-looking aye-aye and their nocturnal behaviors as a demonic predictor of bad luck! Aye-ayes do not harm humans and have no mystical powers, but local folklore has taken hold of some cultures in Madagascar, and many people kill aye-ayes on sight.
Aye-ayes may look strange, but they are perfectly built for their environment and lifestyle. They have large yellow-orange eyes with dark eye rings and bat-like ears that help them hunt effectively at night. They have long fingers, the third one being especially long and thin. These fingers may seem alien-looking but they are the best tool for reaching and hooking yummy grubs from tree holes. Opposable thumbs help them grip and hang from branches. Except for their big toes, they have claws on all their fingers and toes, which allow them to break apart bark. The big toes have flat nails. Their second toe has a “toilet claw,” curved to help groom dirt off their bodies.
Aye-ayes are unique primates, indeed, and perfectly outfitted for their habitats and lifestyles!
Diet
Aye-ayes are mainly insectivorous (they feed on insects) but consume fruits, nuts, nectar, and sometimes fungi. Unlike other primates, the aye-aye has large incisors that continuously grow (similar to rodents) and are worn down with constant use. They use these teeth to make holes or tear up tree bark to find insects. Some researchers think that a diet of more hard nuts than insects is why the aye-aye evolved to have these specialized incisors.
Their abnormally long third finger is a vital feeding tool. They use this finger to tap on branches while they cock their ear to listen for vibrations that indicate potential cavities or moving grubs (insect larvae). Once they detect something interesting, they use their teeth and hands to break through the bark and their long fingers to dig out their prey. They also use their fingers to pierce and scoop out fruit. Grubs are a great source of energy, high in fat and protein. These calories help the aye-aye maintain their energetic activities through the cooler nights.
This form of echolocation-type hunting is complex and unique for primates. Young aye-ayes learn this technique by observing their mothers and then practicing, through trial and error, on their own. This gives us insight into how primates use social learning and experimentation to develop survival skills.
Behavior and Lifestyle
Aye-ayes are almost entirely nocturnal (active at night). As the sun sets and the forest grows dark, aye-ayes stir from their nests in the trees and begin the hunt for food.
They are arboreal (tree-dwelling) but sometimes travel short distances on the forest floor. They use their long, clawed fingers and opposable thumbs to climb horizontal branches and vertical tree trunks. They can even cling upside down as they feed and move about head-first and tail-first.
Biting and tearing apart bark is a messy business, often leaving aye-ayes with dirt, wood dust, and pests stuck in their coarse hair. However, their unique self-grooming habits are a sight to behold. Using their long third finger, the toilet claw, and their tongues, they meticulously clean themselves, a fascinating behavior that sets them apart from other primates.
Aye-ayes are mostly solitary and generally do not form or stay in a family group. However, researchers have reported instances of 2-3 individuals foraging together. So, they will tolerate each other but largely prefer to rest and move around as single units. Other social interactions between aye-ayes occur during mating and when mothers are raising offspring.
Aye-ayes make spherical nests with leaves and branches that can be pretty elaborate. They can use a nest for multiple days in a row or leave it and return later while they make new nests elsewhere. Most nests are occupied by only one individual or a mother and her young.
Aye-ayes are the largest nocturnal lemur.
They have a long, thin third finger with which they tap on tree bark to “echo-locate” grubs.
They were once mistakenly thought to be related to rodents or kangaroos.
They use branches and vines to build bowl-shaped nests high in the tree canopy.
About half an hour before the sun sets, aye-ayes stir awake in their nests and prepare for a night of hunting and foraging. They can travel long distances to search for food. The exception is mothers with young who tend to stay close to the nest. Male aye-ayes travel further than females.
A typical aye-aye night consists of bursts of energetic hunting and feeding in between more extended rest periods. About 19% of their night involves resting in the canopy. When they sleep, they usually wrap their tails around themselves for warmth. They feed for about 14% of the night and dedicate 12% of their active time to self-grooming.
As the night draws to a close, aye-ayes begin their journey back to their resting spots, whether familiar nests or newly constructed ones. These bowl-shaped nests are perched as high as 30-50 feet (10-15m) and are continually modified to ensure their nests are as comfortable as possible.
Aye-ayes are usually found high in the tree canopy and active at night, which makes direct observation of their interactions difficult. Vocalizations are their best-known form of communication. This makes sense for nocturnal, solitary species that are not always close enough to see each other in darkness.
Aye-ayes have a few known vocalizations, each serving a specific purpose. One is a long “creeii” scream call that acts as an immediate attention-grabber among aye-ayes. They make this sound in situations of alarm or agitation, such as when an aye-aye is captured or to make another aye-aye move out of the way. In contrast, a quieter “ggnnoff” sound is a peaceful call often heard when aye-ayes come together, particularly during feeding. Other observed sounds include sneezes, snorts, and whimpers, each with unique context and meaning.
They also use olfactory (sense of smell) signals, such as depositing urine around their nests and feeding branches, to let other aye-ayes know of their presence. Aye-ayes have a urogenital gland that secretes chemicals into their urine. These glandular secretions probably indicate the aye-aye’s age, health, sex, and other identifying information. This kind of olfactory communication is like putting up a billboard advertisement in code — the sender can quickly leave a detailed message that only other aye-ayes can understand, and they do not have to wait around to ensure that the receiver reads the message. It is a convenient method of communicating since they are primarily solitary.
Most of what we know about aye-aye reproduction comes from captive individuals. There is no particular season when aye-ayes mate and females mate with multiple males in a multimale-multifemale mating system.
A female reaches sexual maturity at about two years old. After that, her hormonal cycles determine when she will mate or not. Mating occurs when estrogen hormones peak in the female, and this increase is associated with her vulva (her external genital organ) changing from small and gray to swollen and red. This hormonal peak lasts 2-10 days, during which mating will most likely result in a pregnancy.
A female will mate only when she is ready to accept a male. She will often attack an approaching male if she is not receptive. If she is interested in the male, they touch noses and lick each other’s mouths. They may chase each other along the canopy and he will sniff the genital area of the female. If she accepts him then she will allow him to mate her.
The gestation period, or the time she is pregnant, is about 5-5.5 months, after which she gives birth to a single infant (no twins have been reported yet). Infants weigh between 3- 5 ounces (90-140 g), about a baseball’s weight. The development from infant to adult is slow and takes about two years. Mother aye-ayes will not mate and will only become pregnant once their child leaves the nest.
Infants are born with dark fur (sometimes a few shades lighter than their parents) but have green eyes and floppy ears that eventually change to match adult color and shape. They are also born with softer “baby teeth” or “milk teeth” while they are nursing from their mother. Young aye-ayes spend most of their time in their mother’s nest. The mother tends to stay at the nest and feed on fruits and insects that are close by. She will even open nuts for her young to eat in the nest.
The learning process of young aye-ayes is a crucial part of their development. They spend most of their time in their mother’s nest, observing and mimicking her behaviors. They learn many skills and behaviors by observing their mother, often mimicking the adult behavior of self-grooming and hunting. The young aye-aye also has to learn the specialized echo-location hunting technique from their mother, which takes a while to get right.
The young one’s adult teeth come in when they are four months old and, about a month after, they stop depending on their mother’s milk for food but still stick close to her for protection. By the time aye-ayes are nine months old, they are capable of traveling without their mother
Aye-ayes have a unique niche (or job) in their ecosystem. They eat wood-boring insects that can damage trees and, thereby, help control the population of tree pests. They also eat other fruits and nuts, making them adaptable to various food sources and habitats. This flexibility allows them to take advantage of many forest types and help disperse seeds across the forests. This way, these seeds can find open patches of soil to grow without competing against the parent plant. Their feeding habits help maintain a healthy and diverse forest ecosystem.
Fossa, owls, and snakes are potential predators of aye-ayes, making these primates an important link in the Madagascar food web.
The International Union for Conservation of Nature lists aye-aye as Endangered (IUCN, 2018), appearing on the IUCN Red List of Threatened Species.
Their main threat is human-caused habitat destruction. Humans have changed Madagascar’s wild landscape to make space for agricultural lands and human development to fulfill economic needs. Unfortunately, this has fragmented forests and wildlife populations. Aye-ayes may have existed in lower populations to begin with and the added stress of habitat change has decreased the population drastically.
In local lore, aye-ayes are mistakenly considered evil because of their strange appearance and nocturnal behaviors. An aye-aye is said to bring ill fortune to those who see it, and the only way to prevent these bad events is to kill it. Some locals also kill them because they consider them pests that destroy agricultural trees. These targeted killings of aye-ayes make conserving populations that live on the edge of human development more difficult.
They have a “highest priority” conservation status because they are rare, and their population is fragmented across Madagascar. They were listed in the IUCN’s 2016-2020 Primates at Risk: The World’s 25 Most Endangered Primates publication. It is estimated that there are only between 1,000 and 10,000 individuals left in the wild.
The aye-aye is listed in Appendix I of the Convention on International Trade in Endangered Species (CITES), an international agreement between governments whose goal is to ensure that international trade in specimens of wild animals and plants does not threaten their survival. National laws and African Conventions prohibit regional trade and export of any aye-ayes and their by-products (skins or bones).
Numerous national parks and protected areas in Madagascar help curb habitat degradation and provide some measure of safety for aye-ayes. However, local enforcement of laws against killing these unique primates is difficult to implement.
Estimating the population of these nocturnal creatures is challenging, often done using evidence of feeding signs (holes in trees). The accuracy of long-term population estimates is further complicated by the aye-aye’s elusive nature. To overcome this, scientists are employing genetic studies and advanced field techniques to gain a more precise understanding of wild populations and their preferred habitats, thereby aiding in the conservation of the species.
The Duke Lemur Center (DLC) in Durham, North Carolina, plays a prominent role in aye-aye research and conservation. As one of the first modern captive breeding centers for aye-ayes, their research is focused on reintroducing these endangered lemurs into the wild, thereby contributing significantly to the species’ survival.
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Written by Acima Cherian, June 2024