The aye-aye is a lemur, a strepsirrhine primate native to Madagascar that combines rodent-like
teeth and a special thin middle finger to fill the same ecological niche as a woodpecker.
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.
The only other animal species known to find food in this way is the striped possum. 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.
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.
Etymology The genera, Daubentonia, was named after the
French naturalist Louis-Jean-Marie Daubenton by his student,Étienne Geoffroy Saint-Hilaire,
in 1795. Initially Geoffroy considering using the Greek name, Scolecophagus in refer 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". 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 in 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 in 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. Evolutionary history and taxonomy
Due to its derived morphological features, the classification of the aye-aye has been
debated since its discovery. The possession of continually growing incisors parallels
those of rodents, leading early naturalists to mistakenly classify the aye-aye within
the mammalian order Rodentia and as a squirrel, due to its toes, hair coloring, and tail.
However, the aye-aye is also similar to felines in its head shape, eyes, ears and nostrils.
The aye-aye's classification with the order Primates has been just as uncertain. It has
been considered a highly derived member of the family Indridae, a basal branch of the
strepsirrhine suborder, and of indeterminate relation to all living primates. In 1931,
Anthony and Coupin classified the aye-aye under infraorder Chiromyiformes, a sister
group to the other strepsirrhines. Colin Groves upheld this classification in 2005 because
he was not entirely convinced the aye-aye formed a clade with the rest of the Malagasy
lemurs, despite molecular tests that had shown Daubentoniidae was basal to all Lemuriformes,
deriving from the same lemur ancestor that rafted to Madagascar during the Paleocene
or Eocene. In 2008, Russell Mittermeier, Colin Groves, and others ignored addressing higher-level
taxonomy by defining lemurs as monophyletic and containing five living families, including
Daubentoniidae. Further evidence indicating that the aye-aye
belongs in the superfamily Lemuroidea can be inferred from the presence of a petrosal
bullae encasing the ossicles of the ear. However, interestingly, the bones themselves may have
some resemblance to those of rodents. The aye-ayes are also similar to lemurs in their
shorter back legs. Anatomy and morphology
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. In length, a full-grown aye-aye is typically
about three feet long with a tail as long as its body. Among the aye-aye's signature
traits are its fingers. The third finger, which is thinner than the others, is used
for tapping and grooming, while the fourth finger, the longest, is used for pulling bugs
out of trees. 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 the aye-aye, lesser galago, bat-eared fox,
mouse lemur, and others. Females have two nipples located in the region
of the groin. Behaviour and lifestyle
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. The Aye Aye is a solitary animal
that marks its large home range with scent with the smaller territory of a female often
overlapping 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, and can seemingly tolerate
each other until they hear the call of a female that is looking for a mate.
Diet The aye-aye commonly eats seeds, insect larvae,
fruits, nectar, and fungi, classifying it as an omnivore.
Foraging
Aye-ayes tap on the trunks and branches of the trees they visit up to eight times per
second, and listen to the echo produced to find hollow chambers inside. Once a chamber
is found, they chew a hole into the wood and get grubs out of that hole with their narrow
and bony middle fingers. The aye-aye begins foraging anywhere 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 cross up to 4 km a night.
Though foraging is mostly solitary, they will occasionally forage in groups. Individual
movements within the group are coordinated using both sound and scent signals.
Social systems The aye-aye is classically considered 'solitary'
as they have not been observed to groom each other. However, recent research suggests it
is more social than once thought. It usually sticks to foraging in its own personal home
range, or territory. The home ranges of males often overlap, and the males can be very social
with each other. Female home ranges never overlap, though a male's home range often
overlaps that of several females. The male aye-ayes live in large areas up to 80 acres,
while females have smaller living spaces that goes up to 20 acres. Regular scent marking
with their cheeks and neck is how aye-ayes let others know of their presence and repel
intruders from their territory. Like many other prosimians, the female aye-aye
is dominant to the male. They are not typically monogamous, and will often challenge each
other for mates. Male aye-ayes are very assertive in this way, and sometimes even pull other
males away from a female during mating. Males are normally locked to females during mating
in sessions that may last up to an hour. Outside of mating, males and females interact only
occasionally, usually while foraging. The aye-aye is thought to be the only primate
which uses echolocation to find its prey. Distribution and habitat
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 upwards of 700 meters
altitude. They sleep during the day in nests built in the forks of trees.
Conservation The aye-aye was thought to be extinct in 1933,
but was rediscovered in 1957. Nine individuals were transported to Nosy Mangabe, an island
near Maroantsetra off eastern Madagascar, in 1966. Recent research shows the aye-aye
is more widespread than was previously thought, and its conservation status was changed to
Endangered in 2014. This is for four main reasons: the aye-aye is considered evil, the
forests of Madagascar are being destroyed, the farmers will kill aye-ayes to protect
their crops and for poaching. However, there is no simple solution for the two latter problems.
Madagascar is a very impoverished nation, and without the farmland the Malagasy may
not be able to survive, because while there is poverty there is also overpopulation. Moreover,
the farmers cannot afford to lose crops to aye-ayes and many poachers kill and sell the
aye-ayes simply to survive. As many as 50 aye-ayes can be found in zoological
facilities worldwide. Superstition
The aye-aye is a near-threatened species not only because its habitat is being destroyed,
but also due to native superstition. Besides being a general nuisance in villages, ancient
Malagasy legend said the Aye-aye was a symbol of death.
Researchers in Madagascar report remarkable fearlessness in the aye-aye; some accounts
tell of individual animals strolling nonchalantly in village streets or even walking right up
to naturalists in the rainforest and sniffing their shoes.
However, public contempt goes beyond this. 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 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.
Incidents of aye-aye killings increase every year as its forest habitats are destroyed
and it is forced to raid plantations and villages. Because of the superstition surrounding it,
this often ends in death. Captive breeding
The conservation of this species has been aided by captive breeding, primarily at the
Duke Lemur Center in Durham, North Carolina. This center has been influential in keeping,
researching and breeding aye-ayes and other lemurs. They have sent multiple teams to capture
lemurs in Madagascar and have since created captive breeding groups for their lemurs.
Specifically, they were responsible for the first aye-aye born into captivity, Blue Devil,
and studied how he and the other aye-aye infants born at the center develop through infancy.
They have also revolutionized the understanding of the aye-aye diet.
References
Literature cited