page_title: Black-capped squirrel monkey
section_title: Reproduction
hierarchical_section_title: Black-capped squirrel monkey / Biology / Reproduction
caption_attribution_description: English: Bolivian Squirrel Monkey (Saimiri boliviensis) family. Notice how tight the grip of the baby is even at this young and tender age of a couple of weeks old. Mum was literally flying through the trees, with Dad, yet baby, despite being asleep, still held on tightly. Taken at Apenheul, Apeldoorn, Netherlands
context_page_description: The black-capped squirrel monkey is a species of New-World monkey native to the upper Amazon basin in Bolivia, western Brazil and eastern Peru. They weigh between 365 and 1135 grams and measure, from the head to the base of the tail, between 225 and 370mm. Black-capped squirrel monkeys are primarily tree-dwelling and are found in both native and plantation forests as well as some farmed areas near running water. Their diet is omnivorous and mostly consists of flowers, fruit, leaves, nuts, seeds, insects, arachnids, eggs and small vertebrates. They mostly live in female-dominated troops of around 40 to 75 monkeys, with males having been observed to disperse to live in all-male troops after reaching sexual maturation. Their current conservation status according to the IUCN is 'Least Concern'. The species belongs to the genus Saimiri and has two subspecies, S. b. boliviensis and S. b. peruviensis.
context_section_description: A Black-capped squirrel monkey will typically reach sexual maturation at around 3 years of age for females and 5 years of age for males. The yearly reproductive cycle of mature Saimiri has been observed by several researchers to be affected by a number of environmental factors, including the cycles of rainfall and levels of illumination in their habitat. The mating season coincides with the dry season, and will typically result in a single infant being born to each mother. It has been suggested that adult female monkeys are more receptive to environmental cues for the mating season to begin, and the response in males is in part attributed to behavioural and scent cues from the females.  During the mating season, males of the species will gain a large amount of subcutaneous upper body fat, leading to what is known as a ‘fatted’ appearance. It has also been observed that the testosterone levels of monkeys of the Bolivian and Peruvian species are noticeably higher during the mating season than those of other species of male Saimiri from Guayana. Males will become more irritable and aggressive, fight more frequently for the purpose of achieving dominance within the troop, and engage in genital display towards less dominant males. It has been observed in both natural and laboratory settings that the hierarchy of the troop may change up to as often as three times in a month, and this will often result in highly aggressive fights which may lead to the complete exclusion of younger adult males from the troop. The scent and behavioural cues of a female monkey assist a male in his judgement of whether or not she will be receptive to his approach and attempt at mating with her. If she is not receptive, the female, sometimes with the aid of other nearby females, will usually chase the male away. Consorting and copulation between a male and female monkey may last between one minute and over an hour depending on the presence of other monkeys and the environment in which it takes place. The gestation period of the monkey has been estimated to last between 160 and 170 days. During the first week following its birth, an infant monkey will cling to its mother’s back and will seldom move or be attended to by the mother unless it is in some way in need of assistance.
caption: A family of Saimiri boliviensis
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