In the gloom it came along the branches towards me, its round, hypnotic eyes blazing, its spoon-like ears turning to and fro like radar dishes, its white whiskers twitching and moving like sensors; its black hands, with their thin fingers, the third seeming terribly elongated, tapping delicately on the branches as it moved along.
- from The Aye-aye and I by Gerald Durrell
The aye-aye is the only living representative of its family, Daubentoniidae1. Other names among the Malagasy (the people of Madagascar) include Hay-Hay, Ahay and Aiay. Due to confusion over its appearance it was classified as a rodent in the 18th Century. The aye-aye is so unusual that it is not only strange within the context of primates; it is one of the most distinctive mammals on earth (Mittermeier et al, 1994).
It is, unfortunately, also extremely endangered. It was featured in the Douglas Adams radio show and book Last Chance to See. On 7 April, 2005, the Primate Specialist Group of IUCN - The World Conservation Union's Species Survival Commission (SSC) and the International Primatological Society (IPS), in collaboration with Conservation International (CI) released a report from Madagascar titled, Primates in Peril: The World's 25 Most Endangered Primates - 2004-2006.
More and more, mankind's closest living relatives are being cornered into shrinking areas of tropical forest. This is especially true of Madagascar, one of the planet's biodiversity hotspots that has lost most of its original forest cover. More than half its lemurs are threatened with extinction, none of which are found anywhere else in the world. Without immediate steps to protect these unique creatures and their habitat, we will lose more of our planet's natural heritage forever.
- CI President Russell A Mittermeier, who also chairs the IUCN/SSC Primate Specialist Group
The aye-aye is between 86 and 104cm (30 to 40 inches) in length from the tip of its nose to the end of its long bushy tail, about the size of an average house cat. They have a pale face and coarse, shaggy black fur with a mantle of white. They weigh about two to three kilograms (seven pounds).
The aye-aye has a highly specialised third finger. While most of its digits end in claws, this one has a nail. It uses this extremely long third finger to remove grubs from rotting wood and to find the level of milk in coconuts. It has teeth that continuously grow much like those of rodents do, which are ground down by gnawing. The ears of the aye-aye are large and round; making its face look a bit like a psychotic Mickey Mouse.
Diet and Lifestyle
The aye-aye is a very adaptable creature. Its habitat includes primary and secondary rain forest, deciduous forest, secondary growth, and dry scrub forest. It has also been seen living in cultivated areas, particularly coconut groves (Harcourt and Thornback, 1990). The aye-aye formerly inhabited much of the coastal area of eastern and north-western Madagascar. By 1983, only a few scattered individuals remained on the north-east and north-west coasts. However, sightings increased, and by 1994 it had been reported from a much larger number of locations, including along the entire east coast as well as Antsiranana and Mahajanga provinces, although always at low densities.
The aye-aye reaches sexual maturity around two years of age and mates all year long. Their gestation period is about 160 days. It gives birth to one offspring at a time and will not have another for two to three years. The mother will wean the offspring at around seven months in the wild. Its lifespan in the wild is unknown, but one captive specimen lived for 23 years and three months (Jones, 1982).
The aye-aye is a nocturnal forager. Up to 80 per cent of its night is spent travelling in the upper canopy. The foraging activities are broken up by rest periods that may last up to two hours. The aye-aye is able to leap and climb vertically with ease; horizontal movements are more deliberate, but it does descend to the ground and sometimes covers large distances. Males are capable of travelling between two and four km (1.2 to 2.4 miles) in a single night. The day is spent sleeping in a nest constructed in a tree from interwoven twigs and dead leaves, also in the canopy, in a dense tangle of vines or branches. In one study, eight aye-ayes used over 100 nests in a two year period, with different aye-ayes using the same nest on different occasions. Large trees may contain as many as six nests (Garbutt, 1999). Locations where it is sighted are often below 700m (2,300 feet). However, it has been observed at an altitude of 800m (2,600 feet) and evidence of its feeding has been observed at 1,250m (4,100 feet) (Goodman and Schütz 2000).
The aye-aye is specialised as a night-time primate 'woodpecker'. It taps trees with its long middle finger, listens for wood-boring grubs under the bark, exposes them by gnawing with its rodent-like front teeth, and extracts them with its middle finger. The aye-aye also eats fruits, nuts, nectar, seeds and fungi. It is known to raid coconut plantations and has been seen eating lychee nuts and mangoes (Garbutt, 1999, Macdonald, 2001). In captivity, the aye-aye will eat sugar, mangoes, bananas and eggs.
The aye-aye is a relatively solitary animal, almost all sightings being of a single animal. Eleanor Sterling studied the aye-aye in Madagascar for two years, where she observed them scouting in pairs. The pair of aye-ayes would feed in trees next to one another. One aye-aye would then call to the other one before it moved to another tree, and then the second one would follow. Home ranges of males can overlap considerably with one another, and the common area may be occupied by both males simultaneously. Interactions are sometimes antagonistic, but not always. Female home ranges do not overlap with one another and they rarely interact. When they do, they are invariably aggressive towards one another. Female home ranges do overlap with the home range of at least one male, and both sexes may mate with several partners. Outside of mating, males and females occasionally come together and interact briefly, often when foraging. Aye-ayes scent-mark regularly through urination and also by rubbing their ano-genital region, neck and cheeks on branches. Male aye-ayes have large home ranges, between 100 and 200 hectares (250 to 500 acres). Females' home ranges are much smaller, generally between 30 and 50 hectares (75 to 125 acres) (Garbutt, 1999).
The exact number of aye-ayes is unknown, but it is thought to be between 1,000 and 2,000. In a few villages, it was thought among the Malagasy that anyone who harmed an aye-aye would die within a year; mostly, the aye-aye is thought to be not only vermin, but a bad omen. The potential reasons why are numerous; in most places it was believed that the appearance of an aye-aye signalled the death of one of the villagers, unless it was killed itself. To this day, they are usually shot on sight. Destruction of habitat through logging and conversion to agricultural use is also helping to reduce the number of aye-ayes, forcing them into the farmer's fields to feed.
To help protect the aye-aye, at least 16 reserve areas have been set up throughout Madagascar2, and it was introduced to Nosy Mangabe Special Reserve in 1966. There are six different captive aye-aye programs in the United States, including the Duke Primate Center and the San Francisco Zoo. Elsewhere, captive breeding programs can be found at the Vincennes Zoo in Paris, the Jersey Wildlife Preservation Trust, the Zoo Ivoloina and Parc Tsimbazaza in Madagascar. Other things that have been suggested are conservation education and development programmes among the local people, and compensation for damage to crops caused by aye-ayes. Laws against killing aye-ayes could use better enforcement, too.
Harcourt, C and Thornback, J 1990. Lemurs of Madagascar and the Comoros The IUCN Red DataBook. IUCN, Gland, Switzerland and Cambridge, UK.
Jones, ML 1982. Longevity of captive mammals Zool. Garten. 52:113-28 (original not seen, Nowak, 1991).
Mittermeier, RA, Konstant, WR, Nicholl, ME and Langrand, O (eds), 1992. Lemurs of Madagascar: An action plan for their conservation 1993 - 1999 IUCN, Gland. 58pp.
Garbutt, N 1999. Mammals of Madagascar Yale Univ. Press, New Haven and London.
Macdonald, D 1984. The Encyclopedia of Mammals. Facts On File Publications New York, NY, USA.
Goodman and Schütz, 2000. The lemurs of the northeastern slopes of the Réserve Spéciale de Manongarivo Lemur News 5:32.