The diademed sifaka forms groups typically of two to ten individuals, which may include multiple male and female adults. Each troop defends an exclusive home territory of 25 to 50 hectares (62 to 125 acres) using perimeter
scent territorial marking by both the males and females. Although the diademed sifaka defends the group's territory strongly against other members of their same species, it will share territory with other species such as the
red-bellied lemur and the
common brown lemur.
P. diadema is thought to traverse the greatest daily path distance relative to other members of its family in its patrolling and foraging, attaining a typical travel distance in excess of 1.6 kilometres (one mile) per day. To accomplish this it consumes a diet high in energy content and diverse in plant content, each day consuming over 25 different vegetative species. This
diurnal lemur further diversifies its diet by consuming not only fruits, but certain flowers, seeds and verdant leaves, in proportions that vary by season. For a large lemur, the diademed sifaka is rather athletic, being capable of lateral aerial propulsion of up to 30 kilometers per hour, a result of muscular leg thrusting action pushing off from a vertical tree trunk. It is possible, although not proven, that its vigorous health characteristics are enhanced from high consumption of two plants which contain high concentrations of
alkaloids. This species is
arboreal, and only rarely are seen on the ground; moreover, it is a vertical clinger and lateral leaper. The diademed sifaka makes a warning call resembling the sound "kiss-sneeze" when a
terrestrial predator is perceived; the sole terrestrial predators of
P. diadema are the
fossa and
Nile crocodile. Sexual maturity occurs after age two or three, with the male maturing somewhat more slowly than the female. Little is known of mating behaviour; however, it is believed that the female is
receptive to mating only a few days per year. Being dominant, the female has the greatest input to mate selection. Copulation occurs in the summer (around December), and the expected number of births is one offspring per female per annum. ==Conservation issues==