The diademed sifaka is active during the daytime, when it moves around in groups of eight or more individuals (1), which consist of a number of both adult males and adult females. It was once thought that females remain within the group they were born, whilst males move into neighbouring groups; however, more recent studies show that females may also move between groups (2). Together they defend a home range of 25 to 60 hectares by scent marking (2). The group can travel several hundred metres each day, moving between high in the forest canopy and low in the understorey (2), in their search for leaves, buds, flowers, seeds and fruits on which they feed (6). Occasionally, the diademed sifaka may also descend to the forest floor to search for fallen fruits (2), or to sniff out certain strong smelling plants that parasitize the roots of trees or vines (7).
Mating takes place between January and March, and the diademed sifaka gives birth to a single offspring, after a gestation of 170 to 180 days. The infant initially clings tightly to its mother’s belly, but as it grows, it will instead ride on its mother’s back as she moves through the trees (2). A young sifaka is vulnerable to predation, such as by the carnivorous fosa (Cryptoprocta ferox) (2). To help avoid such dangers, the sifaka will call to warn the others in its group; the presence of a predator on the ground is signalled by a sneeze-like zzuss call, while a honk-honk-honk means a large raptor may be circling overhead (2)