The aye-aye (''Daubentonia madagascariensis'') is a long-fingered
lemur, a
strepsirrhine
Strepsirrhini or Strepsirhini (; ) is a Order (biology), suborder of primates that includes the Lemuriformes, lemuriform primates, which consist of the lemurs of Fauna of Madagascar, Madagascar, galagos ("bushbabies") and pottos from Fauna of A ...
primate
Primates are a diverse order (biology), order of mammals. They are divided into the Strepsirrhini, strepsirrhines, which include the lemurs, galagos, and lorisids, and the Haplorhini, haplorhines, which include the Tarsiiformes, tarsiers and ...
native to
Madagascar
Madagascar (; mg, Madagasikara, ), officially the Republic of Madagascar ( mg, Repoblikan'i Madagasikara, links=no, ; french: République de Madagascar), is an island country in the Indian Ocean, approximately off the coast of East Africa ...
with
rodent
Rodents (from Latin , 'to gnaw') are mammals of the Order (biology), order Rodentia (), which are characterized by a single pair of continuously growing incisors in each of the upper and lower jaws. About 40% of all mammal species are roden ...
-like teeth that perpetually grow and a special thin middle finger.
It is the world's largest
nocturnal
Nocturnality is an ethology, animal behavior characterized by being active during the night and sleeping during the day. The common adjective is "nocturnal", versus diurnality, diurnal meaning the opposite.
Nocturnal creatures generally have ...
primate.
It 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 into 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. 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
Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial n ...
''
Daubentonia'' and
family
Family (from la, familia) is a group of people related either by consanguinity (by recognized birth) or affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its members and of society. Idea ...
Daubentoniidae. It is currently classified as
Endangered
An endangered species is a species that is very likely to become extinct in the near future, either worldwide or in a particular political jurisdiction. Endangered species may be at risk due to factors such as habitat loss, poaching and inv ...
by the
IUCN. A second species, ''
Daubentonia robusta'', appears to have become
extinct at some point within the last 1000 years, and is known from
subfossil
A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved ...
finds.
Etymology
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
John Edward Gray, Fellow of the Royal Society, FRS (12 February 1800 – 7 March 1875) was a British zoology, zoologist. He was the elder brother of zoologist George Robert Gray and son of the pharmacologist and botanist Samuel Frederick 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 "" (cry of exclamation and astonishment). However, American paleoanthropologist
Ian Tattersall
Ian Tattersall (born 1945) is a British-born American paleoanthropologist and a curator emeritus with the American Museum of Natural History in New York City, New York. In addition to human evolution, Tattersall has worked extensively with lemur ...
noted in 1982 that the name resembles the
Malagasy name "hai hai" or "hay hay", (also ''ahay'', ''aiay'', ''haihay''
) which refers to the animal and 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.
Evolutionary history and taxonomy
Due to its
derived morphological features, the classification of the aye-aye was debated following its discovery. The possession of continually growing
incisor
Incisors (from Latin ''incidere'', "to cut") are the front teeth present in most mammals. They are located in the premaxilla above and on the mandible below. Humans have a total of eight (two on each side, top and bottom). Opossums have 18, w ...
s (front teeth) parallels those of
rodent
Rodents (from Latin , 'to gnaw') are mammals of the Order (biology), order Rodentia (), which are characterized by a single pair of continuously growing incisors in each of the upper and lower jaws. About 40% of all mammal species are roden ...
s, leading early naturalists to mistakenly classify the aye-aye within the mammalian order
Rodent
Rodents (from Latin , 'to gnaw') are mammals of the Order (biology), order Rodentia (), which are characterized by a single pair of continuously growing incisors in each of the upper and lower jaws. About 40% of all mammal species are roden ...
ia 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
Basal or basilar is a term meaning ''base'', ''bottom'', or ''minimum''.
Science
* Basal (anatomy), an anatomical term of location for features associated with the base of an organism or structure
* Basal (medicine), a minimal level that is nec ...
branch of the
strepsirrhine
Strepsirrhini or Strepsirhini (; ) is a Order (biology), suborder of primates that includes the Lemuriformes, lemuriform primates, which consist of the lemurs of Fauna of Madagascar, Madagascar, galagos ("bushbabies") and pottos from Fauna of A ...
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.
However, molecular results have consistently placed ''Daubentonia'' as the most
basal
Basal or basilar is a term meaning ''base'', ''bottom'', or ''minimum''.
Science
* Basal (anatomy), an anatomical term of location for features associated with the base of an organism or structure
* Basal (medicine), a minimal level that is nec ...
of
lemurs.
The most parsimonious explanation for this is that all lemurs are derived from a single ancestor that
rafted from Africa to Madagascar during the
Paleogene.
Similarities in dentition between aye-ayes and several African primate fossils (''
Plesiopithecus
''Plesiopithecus '' is an extinct genus of early strepsirrhine primate from the late Eocene.
Anatomy
Originally described from the right mandible (lower jaw), its confusing anatomy resulted in it being classified as an ape—its name tra ...
'' and ''
Propotto'') have led to the alternate theory that the ancestors of aye-ayes colonized Madagascar separately from other lemurs.
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
petrosal bullae encasing the
ossicles of the ear. The aye-ayes are also similar to lemurs in their shorter back legs.
[
]
Anatomy and morphology
A full-grown aye-aye is typically about long with a tail longer than its body. The species has an average head and body length of plus a tail of , and weighs around .[
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 much thinner than the others, is used for tapping, while the fourth finger, the longest, is used for pulling grubs and insects out of trees, using the hooked nail.[ The skinny middle finger is unique in the animal kingdom in that it possesses a ball-and-socket metacarpophalangeal joint, can reach the throat through a ]nostril
A nostril (or naris , plural ''nares'' ) is either of the two orifices of the nose. They enable the entry and exit of air and other gasses through the nasal cavities. In birds and mammals, they contain branched bones or cartilages called t ...
and is used for picking one's nose and eating mucus ( mucophagy) so harvested from inside the nose. 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
Lesser bushbabies, or lesser galagos, are strepsirrhine primates of the genus ''Galago''. They are classified, along with the bushbabies (genus ''Euoticus'') and the rest of the galagos (genera ''Otolemur'', ''Galagoides'', ''Paragalago'', and ''S ...
, 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. 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.
Diet and foraging
The aye-aye is an omnivore
An omnivore () is an animal that has the ability to eat and survive on both plant and animal matter. Obtaining energy and nutrients from plant and animal matter, omnivores digest carbohydrates, protein, fat, and fiber, and metabolize the nut ...
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 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.
]
Social systems
The aye-aye is classically considered 'solitary' as they have not been observed to groom each other. However, recent research suggests that 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 , while females have smaller living spaces that goes up to . It is difficult for the males to defend a singular female because of the large home range. They are seen exhibiting polygyny because of this. 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
Rainforests are characterized by a closed and continuous tree canopy, moisture-dependent vegetation, the presence of epiphytes and lianas and the absence of wildfire. Rainforest can be classified as tropical rainforest or temperate rainfo ...
or dry 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 from interwoven twigs and dead leaves up in the canopy among the vines and branches.
Conservation
The aye-aye was thought to be extinct in 1933, but was rediscovered in 1957. In 1966, nine individuals were transported to Nosy Mangabe, an island near Maroantsetra off eastern Madagascar. Recent research shows the aye-aye is more widespread than was previously thought, but its conservation status was changed to endangered
An endangered species is a species that is very likely to become extinct in the near future, either worldwide or in a particular political jurisdiction. Endangered species may be at risk due to factors such as habitat loss, poaching and inv ...
in 2014. This is for three main reasons: the aye-aye is considered evil, the forests of Madagascar are being destroyed, and the farmers will kill aye-ayes to protect their crops and for poaching. However, there is no direct evidence to suggest aye-ayes pose any legitimate threat to crops and therefore are killed based on superstition.
As many as 50 aye-ayes can be found in zoological facilities worldwide.
Folk belief
The aye-aye is often viewed as a harbinger of evil and death 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 fingers to puncture their victims' aorta.
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 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
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External links
Primate Behavior: Aye-Aye
*ARKive
images and movies of the aye-aye ''(Daubentonia madagascariensis)''
{{Authority control
Mammals described in 1788
EDGE species
Lemurs
Mammals of Madagascar
Taxa named by Johann Friedrich Gmelin
Fauna of the Madagascar lowland forests
Madagascar dry deciduous forests