Central American Squirrel Monkey

The Central American Squirrel Monkey differs in coloration from South American squirrel monkeys. While South American squirrel monkeys tend to be primarily greenish in color, the Central American species has an orange back with olive shoulders, hips and tail and white undersides. The hands and feet are also orange. There is a black cap at the top of the head, and a black tip at the end of the tail. Males generally have lighter caps than females. The face is white with black rims around the eyes and black around the nose and mouth.

There are two subspecies which are similar in coloration, but differ in the shade of the cap. The northern subspecies, living in Central Pacific Costa Rica, has a lighter cap than the southern subspecies, which lives in Panama and in parts of Costa Rica near Panama. The southern subspecies also has more yellowish limbs and underparts.

Adults reach a length of between 266 and 291 millimetres (10.5 and 11.5 in), excluding tail, and a weight between 600 and 950 grams (21 and 34 oz). The tail is longer than the body, and between 362 and 389 mm (14.3 and 15.3 in) in length. As with other squirrel monkeys, there is considerable sexual dimorphism. On average, males weigh 16% more than females. Males have an average body weight of 829 g (29.2 oz) and females average 695 g (24.5 oz). Squirrel monkeys have the largest brains of all primates relative to their body size; the Central American Squirrel Monkey's brain weighs about 25.7 g (0.91 oz), or about 4% of its body weight. Unlike larger relatives, such as the capuchin, spider and howler monkeys, adult Central American Squirrel Monkeys do not have a fully prehensile tail, except as newborn infants, and the tail is primarily used to help with balance.

Diet

The Central American Squirrel Monkey is omnivorous. Its diet includes insects and insect larvae (especially grasshoppers and caterpillars), spiders, fruit, leaves, bark, flowers and nectar. It also eats small vertebrates, including bats, birds, lizards and tree frogs. It finds its food foraging through the lower and middle levels of the forest, typically between fifteen and thirty feet high. Two-thirds to three-quarters of each day is spent foraging for food. It has difficulty finding its desired food late in the wet season, when fewer arthropods are available.

It has a unique method of capturing Tent-making Bats. It looks for roosting bats by looking for their tents (which are made of a folded leaf). When it finds a bat it climbs to a higher level and jumps onto the tent from above, attempting to dislodge the bat. If the fallen bat doesn't fly away in time, the monkey pounces on it on the ground and eats it.

The Central American Squirrel Monkey is an important seed disperser and a pollinator of certain flowers, including the passion flower. While it is not a significant agricultural pest, it does sometimes eat corn, coffee, bananas and mangos. Other fruits eaten include cecropias, legumes, figs, palms, cerillo, quiubra, yayo flaco and wild cashew fruits.

Reproduction

The breeding season for the Central American Squirrel Monkey is in September. All females come into estrus at virtually the same time. A month or two before the breeding season begins, males become larger. This is not due to extra muscle, but to altered water balance within the male's body. This is caused by conversion of the male hormone testosterone into estrogen; thus the more testosterone a male produces, the more he grows in advance of the breeding season. Since males within a group have not been observed fighting over access to females during breeding season, nor attempting to force females to copulate with them, it is believed that female choice determines which males get to breed with females. Females tend to prefer the males that expand the most in advance of breeding season. This may be because the most enlarged males are generally the oldest and the most effective at detecting predators, or it may be a case of runaway intersexual selection.

Males sometimes leave their group for short periods of time during the breeding season in order to try to mate with females from neighboring groups. Females are receptive to males from other groups, although resident males attempt to repel the intruders. The gestation period is six months, and the infants are born within a single week during February and March. Typically, a single infant is born.

Only 50% of infants survive more than six months, largely due to predation by birds. The infant remains dependent on its mother for about one year. Females give birth every 12 months, so the prior infant becomes independent at about the same time the new infant is born. Females become sexually mature at 2½ years old, while males become sexually mature at between 4 and 5 years old. The females leave their natal group upon reaching sexual maturity, while males usually remain with their group for their entire lives. This is different from South American squirrel monkey species, where either males disperse from their natal group or both sexes disperse. Males of the same age tend to associate with each other in age cohorts. Upon reaching sexual maturity, an age cohort may choose to leave the group and attempt to oust the males from another group in order to attain increased reproductive opportunities.

The lifespan of the Central American Squirrel Monkey in the wild is unknown, but captive specimens have been known to live more than 15 years. Other squirrel monkey species are known to be able to live more than 20 years.