Lemur , The family has three genera and nine species, which are confined to Madagascar and the Comoro Islands. Ongoing habitat loss endangers most lemur species. Lemurs resemble advanced primates chiefly in the structure of their hands and feet. The thumb and great toe are well developed and prehensile, and the digits have nails; the second toe of the hind foot of many species has a long claw, which the lemur uses to scratch its soft, luxurious fur. Most lemurs have sharp, pointed muzzles and large eyes. The long tail is never prehensile. Almost all the animals are arboreal and active during the day; they feed primarily on flowers, leaves, and fruit, supplemented by birds' eggs, birds, and insects. Lemurs usually walk on all fours. They are gregarious and usually bear one or two young a year. The ruffed lemur is a common species about 51 to 60 cm (about 20 to 24 in) long. Its thick fur, hanging in fringes on the cheeks and chin and covering its long, bushy tail, is usually black and white. The ring-tailed lemur is active during the day and is partly terrestrial. The gentle lemurs are characterized by a rounded head. A new species, the golden bamboo lemur, was described in 1987. The small, sportive lemurs are now usually placed in their own family. The weasel lemur is chestnut above and lighter brown below and has a white throat. The aye-aye, the only member of its family, is now considered a true lemur. The mouse lemurs, dwarf lemurs, and the fork-marked mouse lemur are closely related to the lorises. The hairy-eared dwarf lemur was first observed alive in the wild in 1989. The colugo, an unrelated mammal, is frequently called the flying lemur .