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The aye-aye (''Daubentonia madagascariensis'') is a long-fingered
lemur Lemurs ( ) (from Latin ''lemures'' – ghosts or spirits) are Strepsirrhini, wet-nosed primates of the Superfamily (biology), superfamily Lemuroidea (), divided into 8 Family (biology), families and consisting of 15 genera and around 100 exist ...
, a
strepsirrhine Strepsirrhini or Strepsirhini (; ) is a suborder of primates that includes the lemuriform primates, which consist of the lemurs of Madagascar, galagos ("bushbabies") and pottos from Africa, and the lorises from India and southeast Asia. Colle ...
primate Primates are a diverse order of mammals. They are divided into the strepsirrhines, which include the lemurs, galagos, and lorisids, and the haplorhines, which include the tarsiers and the simians (monkeys and apes, the latter including huma ...
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 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 rodents. They are na ...
-like teeth that perpetually grow and a special thin middle finger. It is the world's largest
nocturnal Nocturnality is an animal behavior characterized by being active during the night and sleeping during the day. The common adjective is "nocturnal", versus diurnal meaning the opposite. Nocturnal creatures generally have highly developed sens ...
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 The striped possum or common striped possum (''Dactylopsila trivirgata'') is a member of the marsupial family Petauridae. it is found mainly in New Guinea. The species is black with three white stripes running head to tail, and its head has whi ...
. From an ecological point of view, the aye-aye fills the niche of a
woodpecker Woodpeckers are part of the bird family Picidae, which also includes the piculets, wrynecks, and sapsuckers. Members of this family are found worldwide, except for Australia, New Guinea, New Zealand, Madagascar, and the extreme polar regions. ...
, 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 extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...
''
Daubentonia ''Daubentonia'' is the sole genus of the Daubentoniidae, a family of lemuroid primate native to much of Madagascar. The aye-aye ''(Daubentonia madagascariensis)'' is the only extant member. However, a second species known as the giant aye-aye ...
'' and
family Family (from la, familia) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its ...
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 inva ...
by the
IUCN The International Union for Conservation of Nature (IUCN; officially International Union for Conservation of Nature and Natural Resources) is an international organization working in the field of nature conservation and sustainable use of natu ...
. A second species, ''
Daubentonia robusta The giant aye-aye (''Daubentonia robusta'') is an extinct relative of the aye-aye, the only other species in the genus ''Daubentonia''. It lived in Madagascar, appears to have disappeared less than 1,000 years ago, is entirely unknown in life, a ...
'', appears to have become
extinct Extinction is the termination of a kind of organism or of a group of kinds (taxon), usually a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and ...
at some point within the last 1000 years, and is known from subfossil finds.


Etymology

The genus ''Daubentonia'' was named after the French naturalist
Louis-Jean-Marie Daubenton Louis Jean-Marie Daubenton (29 May 1716 – 1 January 1800) was a French naturalist and contributor to the ''Encyclopédie ou Dictionnaire raisonné des sciences, des arts et des métiers''. Biography Daubenton was born at Montbard, Côte-d' ...
by his student,
Étienne Geoffroy Saint-Hilaire Étienne Geoffroy Saint-Hilaire (15 April 177219 June 1844) was a French naturalist who established the principle of "unity of composition". He was a colleague of Jean-Baptiste Lamarck and expanded and defended Lamarck's evolutionary theories ...
, 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, FRS (12 February 1800 – 7 March 1875) was a British zoologist. He was the elder brother of zoologist George Robert Gray and son of the pharmacologist and botanist Samuel Frederick Gray (1766–1828). The same is used for ...
coined the family name Daubentoniidae. The French naturalist
Pierre Sonnerat Pierre Sonnerat (18 August 1748 – 31 March 1814) was a French naturalist, colonial administrator, writer and explorer. He described numerous species of plants and animals on his travels and is honoured in the genus ''Sonneratia'' and in other ...
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 George Shaw may refer to: * George Shaw (biologist) (1751–1813), English botanist and zoologist * George B. Shaw (1854–1894), U.S. Representative from Wisconsin * George Bernard Shaw (1856–1950), Irish playwright * George C. Shaw (1866–196 ...
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 Derive may refer to: * Derive (computer algebra system), a commercial system made by Texas Instruments * ''Dérive'' (magazine), an Austrian science magazine on urbanism *Dérive, a psychogeographical concept See also * *Derivation (disambiguatio ...
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, whe ...
s (front teeth) parallels those of
rodent Rodents (from Latin , 'to gnaw') are mammals of the 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 rodents. They are na ...
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 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 rodents. They are na ...
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 The Indriidae (sometimes incorrectly spelled Indridae) are a family of strepsirrhine primates. They are medium- to large-sized lemurs, with only four teeth in the toothcomb instead of the usual six. Indriids, like all lemurs, live exclusively on t ...
, a basal branch of the
strepsirrhine Strepsirrhini or Strepsirhini (; ) is a suborder of primates that includes the lemuriform primates, which consist of the lemurs of Madagascar, galagos ("bushbabies") and pottos from Africa, and the lorises from India and southeast Asia. Colle ...
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 Colin Peter Groves (24 June 1942 – 30 November 2017) was a British-Australian biologist and anthropologist. Groves was Professor of Biological Anthropology at the Australian National University in Canberra, Australia. Education Born in Englan ...
upheld this classification in 2005 because he was not entirely convinced the aye-aye formed a
clade A clade (), also known as a monophyletic group or natural group, is a group of organisms that are monophyletic – that is, composed of a common ancestor and all its lineal descendants – on a phylogenetic tree. Rather than the English term, ...
with the rest of the Malagasy lemurs. However, molecular results have consistently placed ''Daubentonia'' as the most basal of
lemurs Lemurs ( ) (from Latin ''lemures'' – ghosts or spirits) are wet-nosed primates of the superfamily Lemuroidea (), divided into 8 families and consisting of 15 genera and around 100 existing species. They are endemic to the island of Madaga ...
. 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 The Paleogene ( ; British English, also spelled Palaeogene or Palæogene; informally Lower Tertiary or Early Tertiary) is a geologic period, geologic period and system that spans 43 million years from the end of the Cretaceous Period million yea ...
. 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 translate ...
'' and ''
Propotto ''Propotto'' is an extinct, monotypic genus of early strepsirrhine primate from the early Miocene of Kenya. It contains one described species, ''Propotto leakeyi''. Although long considered a pteropodid fruit-eating bat after spending a brief soj ...
'') have led to the alternate theory that the ancestors of aye-ayes colonized Madagascar separately from other lemurs. In 2008,
Russell Mittermeier Russell Alan Mittermeier (born November 8, 1949) is a primatologist and herpetologist. He has written several books for both popular and scientist audiences, and has authored more than 300 scientific papers. Biography Russell A. Mittermeier is ...
, 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 The metacarpophalangeal joints (MCP) are situated between the metacarpal bones and the proximal phalanges of the fingers. These joints are of the condyloid kind, formed by the reception of the rounded heads of the metacarpal bones into shallow cav ...
, 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 turbi ...
and is used for picking one's nose and
eating mucus Eating mucus is the act of extracting dried nasal mucus with one's finger (rhinotillexis) and the succeeding action of ingesting the mucus from the nose-picking (mucophagy). Health Mucophagy comes with some health risks due to the potential phys ...
(
mucophagy Mucophagy (literally "mucus feeding") is defined as the act of feeding on mucus of fishes or invertebrates. Also, it may refer to consumption of mucus or dried mucus in primates. There are mucophagous parasites, such as some types of sea lice tha ...
) 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 A Fresnel lens ( ; ; or ) is a type of composite compact lens developed by the French physicist Augustin-Jean Fresnel (1788–1827) for use in lighthouses. It has been called "the invention that saved a million ships." The design allows the c ...
, and may be seen in a large variety of unrelated animals, such as lesser galago, bat-eared fox,
mouse lemur The mouse lemurs are nocturnal lemurs of the genus ''Microcebus''. Like all lemurs, mouse lemurs are native to Madagascar. Mouse lemurs have a combined head, body and tail length of less than , making them the smallest primates (the smallest spe ...
, 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 nutr ...
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 Foraging is searching for wild food resources. It affects an animal's Fitness (biology), fitness because it plays an important role in an animal's ability to survive and reproduce. Optimal foraging theory, Foraging theory is a branch of behaviora ...
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 rainfores ...
or
dry deciduous forest The tropical and subtropical dry broadleaf forest is a habitat type defined by the World Wide Fund for Nature and is located at tropical and subtropical latitudes. Though these forests occur in climates that are warm year-round, and may receive ...
, 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 Nosy Mangabe is a small island reserve located in Antongil Bay about 2 km offshore from the town of Maroantsetra in north-east Madagascar. it is accessible by small boat and is part of the larger Masoala National Park complex. It is a tropi ...
, an island near
Maroantsetra Maroantsetra , formerly Louisbourg, is a market town and domestic seaport in Analanjirofo Region, Madagascar, at the northern end of the Bay of Antongil. In 2005 it had a population of 42,529 people. History Maurice Benyovszky arrived in Maroant ...
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 inva ...
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 The Sakalava are an ethnic group of Madagascar. They are found on the western and northwest region of the island, in a band along the coast. The Sakalava are one of the smaller ethnic groups, constituting about 6.2 percent of the total populatio ...
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 The aorta ( ) is the main and largest artery in the human body, originating from the left ventricle of the heart and extending down to the abdomen, where it splits into two smaller arteries (the common iliac arteries). The aorta distributes o ...
.


Captive breeding

The conservation of this species has been aided by captive breeding, primarily at the
Duke Lemur Center The Duke Lemur Center is an sanctuary for rare and endangered strepsirrhine primates, located at Duke University in Durham, North Carolina. It is the largest sanctuary for strepsirrhine primates in the world. The center is open to the public ...
in
Durham, North Carolina Durham ( ) is a city in the U.S. state of North Carolina and the county seat of Durham County, North Carolina, Durham County. Small portions of the city limits extend into Orange County, North Carolina, Orange County and Wake County, North Carol ...
. 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

* * * * * * * *


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