Squirrel Monkey (Bolivian black-capped)

A squirrel monkey at ZSL London Zoo

Black capped or Bolivian squirrel monkeys are a South American squirrel monkey species. Find out more about them: 

What they look like

Squirrel monkey fur is short and close, coloured olive 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 their German name, 'skull monkeys'.

Animal facts

  • The squirrel monkeys are the New World monkeys of the genus Saimiri. They are the only genus in the subfamily Saimirinae.
  • Squirrel monkeys grow to 25 to 35 cm, plus a 35 to 42 cm tail. They weigh 750 to 1100g. Remarkably, the brain mass to body mass ratio for squirrel monkeys is 1:17, which gives them the largest brain, proportionately, of all the primates.
  • Unlike the 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 are extremely speedy.
  • 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.
  • The mating of the squirrel monkeys is subject to seasonal influences. Females give birth to young during the rainy season, after a 150- to 170-day gestation.

What they eat

Mainly insects, topped up with fruit and seeds.


Rainforest, spending the majority of their time in the canopy occasionally scavenging on the forest floor.

Where they live

The upper Amazon in Peru, Brazil and Bolivia.


Small monkeys like these are a tasty treat for larger carnivores, so they seek safety by living in troops. The squirrel monkey’s status in the wild is threatened from use in biomedical research and as pets, bait and food.

Currently ZSL London Zoo, along with other zoos in England, is involved in breeding programmes aimed at increasing numbers of this primate species. Our squirrel monkeys are part of the European Endangered Species Programme.

Visit our squirrel monkeys