Widely considered as the most beautiful of Madagascan primates, the Diademed sifaka has a bare, black or dark gray face framed with white hair, with a patch of black on the top of its head. Its head resembles a ‘diadem’ or ornamental headband worn by royalty, and is the source of its English name. In addition to its unmistakable appearance, this lemur is also known for its large size, being the second largest lemur alive today after the indri.
Diademed sifakas are almost totally arboreal, but may forage or play on the ground. These animals are diurnal and social, and live in groups numbering 2 to 9 animals. These groups may have several breeding females and several breeding males, along with sub-adults and infants. Members of the group may be related, especially the females. It used to be believed that females remained within their birth group, whereas males move into groups nearby, but more recent studies report that females may move between groups as well. Vocalizations are mainly used to maintain group cohesion. Groups have distinct territories of 20 to 30 ha, and mark them by the use of scent. Males do scent marking twice as often as the females, and the frequency doubles near the territorial boundaries.
Diademed sifakas are polygynous and have a hierarchy system for mating, whereby only the dominant male seems to mate with the females. Subdominant males may act aggressively toward the dominant male and try to stop him from mating. The season for mating occurs in the summer months of December and January. The gestation period is about six months, and one or two offspring are born in the winter. The young may nurse for as long as until the age of 2, however, by this time their mother's milk is not a substantial part of their nutrition. The mother also provides protection, grooming, and socialization for her young. Diademed sifakas reach maturity when they are four years old for females, whereas males are mature at five years old.
Diademed sifakas are under threat by habitat destruction, which occurs mainly through slash-and-burn agriculture but also because of logging. They are also hunted as a food source, even in the protected areas. Diademed sifakas are subject to predation by avian predators and probably fossas.
According to the Wikipedia resource, the total Diademed sifaka population size is 6,000 - 10,000 individuals. Today this species’ numbers are decreasing and it is classified as Critically Endangered (CR) on the IUCN Red List.
As frugivores, Diademed sifakas have a role in dispersing seeds, and, as prey items, they may have an impact on predator populations.