Lemur

Lemurs are primitive monkeys that originally inhabited parts of North America, Eurasia, and Africa, but competition with monkeys and apes resulted in their present distribution, restricted to Madagascar. Humans arrived on Madagascar about two thousand years ago, contributing to extinctions of one third of the island's species through habitat destruction, hunting, climate change, and perhaps new diseases. Most lemurs are highly endangered. Most lemurs are arboreal (tree-dwelling), although ring-tailed lemurs spend more time on the ground. Lemurs subsist primarily on three to four food species, consisting of a mix of leaves, fruit, buds, bark, and shoots, but favored foods can vary monthly or seasonally. The golden bamboo lemur tolerates high levels of cyanide in the bamboo shoots. The smaller, nocturnal lemurs and the ayeaye eat more insects. Several species are cathemeral (active during parts of day and night), and there are also diurnal (day-active) forms, such as ring-tailed lemurs or indris. The diurnal species mayhave a nocturnal past, because they share certain features with nocturnal lemurs, including seasonal breeding, female dominance, and reliance on scent for communication.

Unique Primates
Lemurs exhibit many types of social organization. They are solitary in smaller nocturnal forms, while larger diurnal or cathemeral forms live in pairs that sometimes congregate in larger groups, usually with 1:1 sex ratios. Lemurs lack sexual dimorphism, and if there is a difference, females are larger than males. In social species, females largely dominate males, to the extent that males signal submissiveness to all females independent of context. This unusual primate pattern may be due either to seasonally low food productivity and the resulting reproductive costs, or may be partly a function of extinctions of raptors that preyed on primates. Lemurs range in size from the pygmy mouse lemur at thirty-one grams (about one ounce) to the indri at seven kilograms (sixteen pounds), although many extinct forms were larger. All lemurs have longer posterior than anterior limbs, and their anatomy reflects their ability to practice vertical clinging and leaping. This is most developed in the sifakas and indris, which generally position themselves vertically while in the trees, leap from tree to tree, and exhibit a leaping, kangaroo-like gait when on the ground. Cheirogaleidae include the fat-tailed and greater dwarf lemurs, primates that hibernate forupto six months during the dry season. Many of the females in Cheirogaleidae, Megaladapidae, and Lemuridae carry offspring in their mouths and sometimes park them on branches when active. The aye-aye has a high brain-to-body ratio and also has incisors that grow throughout its life (as in rodents) resulting in a dental formula of 1-0-0-3. The teeth are used to gnaw on dead wood during searches for grubs that are then removed with a lengthy third finger.