About Pithecia pithecia (Linnaeus, 1766)
Pithecia pithecia, commonly called the white-faced saki, is a species of New World saki monkey. This small-bodied Neotropical primate lives in Brazil, French Guiana, Guyana, Suriname, and Venezuela. This species feeds mainly on fruits, nuts, seeds, and insects. While it is an arboreal species and a specialist at brachiation, it also travels on the ground when foraging. In its natural habitat, the typical life expectancy of this species is around 14 years, though captive individuals have been recorded living up to 36 years. White-faced sakis are diurnal, and sleep at high elevations of 15–20 m (49–66 ft) in leafy trees, which shelter them from bad weather and flying predators. A subspecies formerly recognized as P. p. chrysocephala was elevated to full species status as P. chrysocephala in 2014. White-faced saki pairs only breed once per year, and do not breed seasonally. The estimated typical breeding season falls in August and September, but breeding has also been observed in March, April, and June. Mating is typically not private, and sometimes occurs while other group members watch. No matter the timing or context of reproduction, female white-faced sakis only give birth to one offspring at a time. Peak birth months usually fall between February and June. In captivity, female white-faced sakis have ovarian cycles of approximately 17 days, and a gestation period of 20–21 weeks. After birth, the mother experiences an average of 23 weeks of lactationally-induced infertility. After an infant is born, the father spends a large amount of time near the infant and mother, likely to protect both from predators. During this period, the mother grooms and cares for the offspring until it becomes independent, while males provide no paternal care at all. Once independent, offspring usually remain in and contribute to the group they were born into. Mature females that still live with their parents do not reproduce. White-faced sakis practice both monogamy and polygamy, and are defensive about keeping other groups away from their females. The white-faced saki mating system has two goals: exclude outsider groups from accessing their females, and reduce within-group competition over females. White-faced sakis show noticeable sexual dimorphism in coloration. Females have shorter hair than males, with brownish-grey fur and white or pale brown stripes around the corners of the nose and mouth. Males have darker, blacker fur, with a reddish-white forehead, face, and throat; their faces are much whiter than females' faces. There is little to no size difference between male and female white-faced sakis. Both genders have relatively small bodies: males usually weigh around 1.73 kg (3.8 lb), and females usually weigh around 1.52 kg (3.4 lb). Within the species' social hierarchy and group social bonds, males are clearly dominant, and the oldest male is typically the most dominant individual in a group. Young male sakis are often mistaken for females because they sometimes have grizzled dorsal hair and orangish bellies. Sexual differences begin to appear at approximately 2 months of age, and gradually become more distinct over the course of several years.
