Source: and
Marmosets are species of New World monkeys belonging to several genera of the Callitrichidae family. An extensive website devoted to the common marmoset reveals plenty of information on how the animals live in the wild and how they should be managed in captivity.
The common marmoset (Callithrix jacchus) is often featured in zoos. It is a small species of monkey; the body measures 19-25 cm and the tail is 27-35 cm long. Females weigh about 300 grams, while males are heavier: 450 grams. Their coat is brown-grey with stripes on the back, a darker head and a white spot on the forehead. The tail is striped in rings. Their most striking feature is white tufts of hair on the sides of the head.

Common marmosets are social animals who live in groups in the wild. In captivity, these animals must also be kept in large or small groups. In the wild, marmosets feed on fruits, insects, lizards, eggs, small birds and tree gum. Feeding them in captivity involves offering a varied diet rich in animal protein several times a day. Because a good deal of each day in the wild is spent looking for food, a number of forms of environmental enrichment can be used to simulate this in a zoo.

The marmoset site (see link) is an initiative of the University of Stirling (Scotland), the Primate Society of Great Britain, and the National Centre for the Replacement, Refinement and Reduction of Animals in Research. An extensive section of the site provides descriptions of the animals’ behaviour, illustrated with films and photographs. A quiz is available so that site visitors can test their knowledge of common marmoset behaviour. There is also a clear explanation of why common marmosets are unsuitable as pets.