The common squirrel monkey is captured for the pet trade and for medical research but it is not threatened. Two squirrel monkey species are threatened: the Central American squirrel monkey and the black squirrel monkey are listed as Vulnerable by the IUCN.
Squirrel monkey fur is short and close, colored black at the shoulders and yellowish orange on its back and extremities. Their throat and the ears are white and their mouths are black. The upper part of their head is hairy. This black-and-white face gives them the name "death's head monkey" in several Germanic languages (e.g., German Totenkopfaffen, Swedish dödskalleapor, Dutchdoodshoofdaapjes) and Slovenian (smrtoglavka).
Squirrel monkeys grow from 25 to 35 cm long, plus a 35 to 42 cm tail. Male squirrel monkeys weigh 750 to 1100 g. Females weigh 500 to 750 g. They are equipped with a long and hairy tail, flat nail, curved small hallux and, pointed claws. Female squirrel monkeys have a pseudo-penis that they use to display dominance over smaller monkeys, in much the same way that the male squirrel monkeys display their dominance.
Behavior and Ecology Edit
Like most of their New World monkey relatives, squirrel monkeys are diurnal and arboreal. Unlike other New World monkeys, their tail is not used for climbing, but as a kind of "balancing pole" and also as a tool. Their movements in the branches can be very rapid. They live together in multi-male/multi-female groups with up to 500 members. These large groups can, however, occasionally break into smaller troops. They have a number of vocal calls, including warning sounds to protect themselves from large falcons, which are a natural threat to them. Their small body size also makes them susceptible to predators such as snakes and felids. For marking territory, squirrel monkeys rub their tail and their skin with their own urine.
Squirrel monkeys are omnivores, eating primarily fruits and insects. Occasionally, they also eat seeds, leaves, flowers, buds, nuts, and eggs. Squirrel monkey mating is subject to seasonal influences. Females give birth to young during the rainy season, after a 150- to 170-day gestation. Only the mothers care for the young. Saimiri oerstedti are weaned by 4 months of age, while S. boliviensis are not fully weaned until 18 months old. Female squirrel monkeys reach sexual maturity at age 2–2.5 years, while males take until age 3.5–4 years. They live to about 15 years old in the wild, and over 20 years in captivity. Menopause in females probably occurs in the mid-teens.