Indris are active during the day and are most at home in the trees, where they feed on leaves, flowers and fruit, but they do occasionally descend to the forest floor to cross small treeless areas or to eat soil (4) (6). On the ground they cannot walk on all fours and so move around on their back legs, standing upright and holding their arms outstretched for balance, skipping in a unique fashion through the forest (6).
These primates are social animals, living in family groups of two to five individuals, consisting of two adults and their offspring (6) (7). The adult female is dominant to the male. Females are often larger in size as they need to forage for more food than the male to feed themselves and their young (6). The male’s role is to defend the territory, and mark the boundaries with urine and secretions from its glands in the muzzle (5) (7). The indri has a characteristic call, consisting of a series of howls, which serve to unite groups, express territoriality, and convey information about age, sex and reproductive ability (6).
Breeding is seasonal, followed by a gestation period of more than five months. The female only gives birth to single offspring at a time, which develop more rapidly than the young of comparable sized primates (4). The young are born with the same colouration and features as the adult indris and are carried across the belly and later on the females back (6). Infant mortality is high, with 50 percent of infants dying before they are two years old from falls, injuries or illnesses, and sexual maturity comes late, after nine years for females (4). The fact that females only reproduce once every two to three years and that there are high infant mortality rates, adds to their population problem; their relatively slow breeding cycles cannot compete with their declining numbers (6).