The tree-dwelling Milne-Edwards’ sifaka lives in groups of 3 to 9 individuals, with each group containing mature members of each sex. These groups, in which females are the dominant sex, occupy large home ranges covering 45 to 55 hectares (2). Both male and female sifakas regularly mark their territory with scent, a behaviour that also communicates information about the scent-marker to other members of the group (2).
Milne-Edwards’ sifaka infants are generally born in June and July, after a gestation period of 180 days, resulting in lactation coinciding with the peak fruiting season. The infant, which weighs just 150 grams at birth, spends the first month of life clinging to its mother’s belly, after which it will ride on her back when moving through the forest (2). Females breed every other year, although the loss of an infant causes the female to breed again the following year. Unfortunately this is a frequent occurrence; 40 percent of infants die within their first year and 65 percent do not survive to sexual maturity. These high mortality rates are due to predation by the fossa (Cryptoprocta ferox), large raptors, and occasional infanticide by males and females entering a new group (2).
If they survive infancy, females reach sexual maturity at four years of age, and males at five years. Females may either remain in the group into which they were born or move to a nearby group, while males move out of their birth group to join another group between five and ten years of age (2). Milne-Edwards’ sifaka lives for up to 35 years (5).
The diet of Milne-Edwards’ sifaka contains a variety of seeds and new leaves, from which it obtains most of the necessary fat and protein (5), as well as fruits and flowers (2). Milne-Edwards’ sifaka moves through the forest canopy to forage for this varied diet (up to 25 species are consumed in just one day), and occasionally, it will descend to the ground to feed on soil. This rather bizarre food item is thought to provide the sifaka with important nutrients, or help neutralise poisons that accumulate from its regular diet (2). The upper parts of the forest are also preferred for sleeping; typically a branch situated eight to ten metres off the ground is selected, probably to avoid any nocturnal predators stalking the ground (2).