Aye-aye

Appearance

It is the world's largest nocturnal primate, and is characterized by its unusual method of finding food: it taps on trees to find grubs, then gnaws holes in the wood using its forward slanting incisors to create a small hole in which it inserts its narrow middle finger to pull the grubs out. This foraging method is called percussive foraging, and takes up 5–41% of foraging time. The only other animal species known to find food in this way is the striped possum.[8] From an ecological point of view, the aye-aye fills the niche of a woodpecker, as it is capable of penetrating wood to extract the invertebrates within.

A full-grown aye-aye is typically about three feet long with a tail longer than its body. The species has an average head and body length of 14–17 inches (36–43 cm) plus a tail of 22–24 inches (56–61 cm), and weighs around 4 pounds (1.8 kg).

Young aye-ayes typically are silver colored on their front and have a stripe down their back. However, as the aye-ayes begin to reach maturity, their bodies will be completely covered in thick fur and are typically not one solid color. On the head and back, the ends of the hair are typically tipped with white while the rest of the body will ordinarily be a yellow and/or brown color.

Among the aye-aye's signature traits are its fingers. The third finger, which is thinner than the others, is used for tapping, while the fourth finger, the longest, is used for pulling bugs out of trees, using the hooked nail. The middle finger is unique in that it possesses a ball-and-socket metacarpophalangeal joint.[21] The aye-aye has also evolved a sixth digit, a pseudothumb, to aid in gripping.

The complex geometry of ridges on the inner surface of aye-aye ears helps to sharply focus not only echolocation signals from the tapping of its finger, but also to passively listen for any other sound produced by the prey. These ridges can be regarded as the acoustic equivalent of a Fresnel lens, and may be seen in a large variety of unrelated animals, such as lesser galago, bat-eared fox, mouse lemur, and others.

Females have two nipples located in the region of the groin.

Naming

The genus Daubentonia was named after the French naturalist Louis-Jean-Marie Daubenton by his student, Étienne Geoffroy Saint-Hilaire, in 1795. Initially, Geoffroy considered using the Greek name Scolecophagus ("worm-eater") in reference to its eating habits, but he decided against it because he was uncertain about the aye-aye's habits and whether other related species might eventually be discovered. In 1863, British zoologist John Edward Gray coined the family name Daubentoniidae.

The French naturalist Pierre Sonnerat was the first to use the vernacular name "aye-aye" in 1782 when he described and illustrated the lemur, though it was also called the "long-fingered lemur" by English zoologist George Shaw in 1800—a name that did not stick. According to Sonnerat, the name "aye-aye" was a "cri d'exclamation & d'étonnement" (cry of exclamation and astonishment). However, American paleoanthropologist Ian Tattersall noted in 1982 that the name resembles the Malagasy name "hai hai" or "hay hay", which is used around the island. According to Dunkel et al. (2012), the widespread use of the Malagasy name indicates that the name could not have come from Sonnerat. Another hypothesis proposed by Simons and Meyers (2001) is that it derives from "heh heh", which is Malagasy for "I don't know". If correct, then the name might have originated from Malagasy people saying "heh heh" to avoid saying the name of a feared, magical animal.

Distribution

The aye-aye lives primarily on the east coast of Madagascar. Its natural habitat is rainforest or deciduous forest, but many live in cultivated areas due to deforestation. Rainforest aye-ayes, the most common, dwell in canopy areas, and are usually sighted above 70 meters altitude. They sleep during the day in nests built in the forks of trees.

Status

The aye-aye is the only extant member of the genus Daubentonia and family Daubentoniidae. It is currently classified as Endangered by the IUCN; and a second species, Daubentonia robusta, appears to have become extinct at some point within the last 1000 years.

Behavior

The aye-aye is a nocturnal and arboreal animal meaning that it spends most of its life high in the trees. Although they are known to come down to the ground on occasion, aye-ayes sleep, eat, travel and mate in the trees and are most commonly found close to the canopy where there is plenty of cover from the dense foliage. During the day, aye-ayes sleep in spherical nests in the forks of tree branches that are constructed out of leaves, branches and vines before emerging after dark to begin their hunt for food. Aye-aye are solitary animals that mark their large home range with scent. The smaller territories of females often overlap those of at least a couple of males. Male aye-ayes tend to share their territories with other males and are even known to share the same nests (although not at the same time), and can seemingly tolerate each other until they hear the call of a female that is looking for a mate.

Food

The aye-aye is an omnivore and commonly eats seeds, fruits, nectar and fungi, but also insect larvae and honey. Aye-ayes tap on the trunks and branches of trees at a rate of up to eight times per second, and listen to the echo produced to find hollow chambers. Studies have suggested that the acoustic properties associated with the foraging cavity have no effect on excavation behavior. Once a chamber is found, they chew a hole into the wood and get grubs out of that hole with their highly adapted narrow and bony middle fingers. The aye-aye begins foraging between 30 minutes before and three hours after sunset. Up to 80% of the night is spent foraging in the canopy, separated by occasional rest periods. It climbs trees by making successive vertical leaps, much like a squirrel. Horizontal movement is more difficult, but the aye-aye rarely descends to jump to another tree, and can often travel up to 4 km (2.5 mi) a night.

Though foraging is usually solitary, they occasionally forage in groups. Individual movements within the group are coordinated using both vocalisations and scent signals.

Cultural

The aye-aye is often viewed as a harbinger of evil and killed on sight. Others believe, if one points its narrowest finger at someone, they are marked for death. Some say that the appearance of an aye-aye in a village predicts the death of a villager, and the only way to prevent this is to kill it. The Sakalava people go so far as to claim aye-ayes sneak into houses through the thatched roofs and murder the sleeping occupants by using their middle finger to puncture the victim's aorta.