Saving species from extinction

Aye-Aye

Scientific name – Daubentonia madagascariensis

Background: This weird and wonderful lemur is without doubt the world’s most unusual and unique primate. Long persecuted in its native Madagascar as an omen of death and evil, the aye-aye, like most of its lemur relatives, faces imminent extinction because of the added pressure of deforestation. This elusive species is the largest nocturnal primate and is the island’s answer to the woodpecker as its specially adapted, elongated, flexible and skeletal third finger is used to find nutritious grubs and winkle them out from their woody burrows, much in the same way as a woodpecker’s beak.

Due to the aye-aye’s precarious situation in the wild, Durrell has been working with the Government of Madagascar since Gerald Durrell’s 1990 expedition to collect 6 of the species to provide an assurance population in Jersey. This breeding programme has to date successfully bred 8 new animals at our Jersey site and there has been subsequent collaboration with other institutions to ensure genetic diversity amongst the captive population.

The Trust has well-established links with the Malagasy people and government, especially involving the conservation of lemurs, and is part of the Madagascar Fauna Group. Since 1964, a great deal of expertise has been gained both at Durrell in Jersey and in the wild with various species. As well as captive breeding, vitally important habitat protection, research, education and training programmes are
ongoing. A number of Madagascan students have completed the course at Durrell’s International Training Centre and returned home with the skills they need to carry out such work and help save their native wildlife.

Species Classification: Lemurs are primates found only on the island of Madagascar, which has been separated from East Africa for over 100 million years. Without competition from other primates, the lemurs evolved into many different kinds, from the size of a mouse to that of a panda. Humans arrived on the island just 1500 years ago, and since then about a third of the different lemurs that existed (mostly large, relatively slow-moving ones) have become extinct, and about 80% of those remaining are threatened with the same fate. The aye-aye is very different from any other species of lemur and is the only member of the family Daubentoniidae. A second member of this family was the giant aye-aye, Daubentonia robusta, which no longer exists and was probably driven to extinction by humans. In Malagasy, aye-aye can mean something that someone does not want to talk about. So, because of local superstition, this lemur is thought to have got its name because people do not like talking about it!  

Description: This unique primate is strictly nocturnal, and its huge, staring orange eyes are well adapted for night vision. The aye-aye’s fur is mainly dark brown to black, with long, white-tipped hairs scattered throughout. It has a long, bushy tail and sparse fur on the face, making it pinkish. Its massive naked ears are highly mobile and give the aye-aye incredibly sensitive hearing. Once mistakenly classified as a rodent, the aye-aye’s front teeth never stop growing and are incredibly efficient at gnawing, just like a rodent’s. They can even bite their way through concrete and aluminium! Aye-ayes, like all other lemurs, have claws, rather than nails. Another special characteristic of the aye-aye is the position of its nipples; they are near the genitals, rather than in the armpit and chest area like those of other primates. However, the most specialist feature of all is the third digit of their hands, which is thinner, longer and more flexible than the others (the increased flexibility is enabled by ball-and socket joints, like those of shoulders and hips).

This finger-tool is used for probing in crevices for invertebrate prey. Male and female aye-ayes are similar in size and appearance; adults have a body about 40cm (15½in) long (without tail, which is around the same length) and weigh around 2½kg (5½lb).

Distribution and habitat: The aye-aye is one of the most widely distributed Madagascan primates, where forests still remain. It appears to only be completely absent from the southwestern part of the island, where subfossils of its close relative, the giant Black & white lemur species factsheet. © Durrell Wildlife Conservation Trust, July 2006, photograph credit: James Morgan aye-aye, have been found. Aye-ayes live in primary and secondary rainforest, deciduous forest and dry scrub forest, as well as areas of cultivated trees, particularly coconut and lychee.

Nocturnal in its habits, the aye-aye sleeps during the day in a nest built in the top of large trees out of twigs and dead leaves. An individual may make a nest to use once or on several consecutive days. In one study, over 2 years, just 8 adults used over 100 nests, and different individuals used the same nest on different days. Large trees may contain as many as 6 aye-aye nests amongst their branches and vine tangles. Most aye-aye activity takes place high up in the canopy, but if it has to cross areas of ground between trees, it does so on all fours.

Feeding habits: Up to 80% of the night is spent foraging and travelling high in the trees, with distances of 2-4km able to be covered in a single night. Like diurnal mammals, nocturnal ones rest during their active period, and an aye-aye’s foraging sessions are punctuated by inactive periods of up to 2 hours. The aye-aye’s diet is quite specialised and seasonally variable – it depends on what is available at a certain time of year. Its most important natural foods are the ramy nut, the hard shell of which the aye-aye is able to crack open with its chisel-like front teeth; nectar from the traveller’s tree, some fungi and insect grubs. Cultivated crops are also raided opportunistically, such as sugar cane, lychees, mangoes and coconut, which brings the aye-aye and local people into conflict.  

The aye-aye spends much of its foraging time hunting for nutritious and energy-rich insect larvae. It does this by locating cavities under bark and inside branches and rotting wood by tapping with its long middle finger. Once it hears the movement of its prey within, the aye-aye gnaws an access hole and uses its special finger again to winkle out the juicy grub. Despite its preference for invertebrate finger-food, the aye-aye has diverse tastes, but captive animals are fussy eaters; individuals have certain preferences and dietary variety is much appreciated.

Breeding and social behaviour: Aye-ayes are largely solitary and male aye-ayes move through large home ranges, between 100 and 200ha (40-80acres), which often overlap to a substantial degree. When males meet, their interactions are often aggressive, as they are in competition for resources and females. Females have much smaller home ranges of 30-50ha (12-20acres), which do not overlap with one another, so they very rarely interact, but are very aggressive when they do. Males and females occasionally come together and interact for brief periods, usually while foraging. Regular scent marking with their cheeks, neck and genitals is a way that aye-ayes let others know of their presence and repel intruders from their territory.

Aye-ayes do not have a fixed breeding season, but at the onset of their 3-day receptive period, females move quickly around their home range, advertising their condition to nearby males with distinctive calls. These calls attract the attention of several males, who gather around a female and fight each other for a chance to mate with her. Mating last for about an hour and takes place in an upside-down position underneath a branch, and rivals try to dislodge the male who won the scramble. Afterwards the female moves to another location and repeats her call, which means that both males and females may get to mate with several partners. Females build a particularly dense nest to give birth in. A single baby, which weighs about 100g, is usually produced after a pregnancy of 23-24 weeks, and stays in the nest for about 8 weeks. Aye-aye infants develop slowly compared to other lemurs and have a long period of pendence on their mother, perhaps over two years in the wild.

Females are thought to have a 2-3 year interval between births and sexual maturity is reached at about 3½ years. Aye-ayes are thought to have a lifespan of around 20 years, like most other lemurs. The oldest aye-aye in captivity reached 23 years, but longevity in the wild has not been recorded.

Conservation status: The World Conservation Union (IUCN) currently classifies the aye-aye as Endangered on the Red Data List, which means that it faces a very high risk of extinction in the near future. Since 1975 it has also been listed under Appendix I of CITES (the Convention on International Trade in Endangered Species of Wild Fauna and Flora).

This affords the species the highest degree of protection against any international trade. The current size of the aye-aye population level is unknown, but the species only occurs at low densities and appears to be rare throughout its range. They are found in 16 of Madagascar’s protected areas. It has so far proved impossible to estimate the number of aye-ayes remaining in Madagascar. Further fieldwork is needed to assess the status and distribution of this enigmatic species of lemur. The main threat to the aye-aye’s survival is habitat loss – large tracts of forest are needed to sustain viable populations, because of the relatively low density of animals. The treatment of aye-ayes by humans does vary between areas, depending Black & white lemur species factsheet. © Durrell Wildlife Conservation Trust, July 2006, photograph credit: James Morgan on religious beliefs and folklore. Although they are often killed on sight as harbingers of evil, some people regard them as ancestral spirits that bring good luck and leave them alone.

The future: Continued research in captivity and the expansion of the aye-aye breeding programme is important to maintain and strengthen the safety net population. In addition, the implementation of further programmes to research and monitor the wild aye-aye population, as well as to protect what remains of their habitat and educate their human coinhabitants, is vital.  Without such measures this unique and fascinating species of primate may soon be lost from the forests of Madagascar forever.

June 2006

Posted 26 October 2006

 
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