Because of their natural social organization (see "Social Behavior," below), it is recommended that callitrichids and Goeldi's monkeys be maintained in stable male-female pairs or small family groups. Nonrelated adults of the same sex should not be housed together unless they are very familiar with each other and no adult of the other sex is present. If breeding is not desired, same-sex siblings can live together. In cases where a conspecific companion is not available, the monkeys can be housed with a companion from a related species of callitrichid. Captive animals engage in many normal social activities with companions belonging to related species.
If single-cage housing is unavoidable, it might be possible to house pairs in adjacent cages and provide either full visual contact or a "contact window" that allows some social interactions between familiar individuals. If singly housed animals are given temporary access to a companion, the same animals should always be placed together. Colony managers have found that some animals cannot be successfully paired with a social companion, because of either extreme aggression or extreme submissiveness. Therefore, the type and degree of social stimulation provided to animals should be carefully monitored.
Wild marmosets, tamarins, and Goeldi's monkeys consume a varied diet that includes tree exudates (sap or gum), fruits, buds and flowers, nectar, insects, and small vertebrates. Much of their time is spent in foraging. Marmosets and pygmy marmosets have specialized dentition for gouging holes in trees from which exudate can be extracted and in the wild obtain much of their food that way. Foraging for tree gums takes up most of the time of wild pygmy marmosets (Soini 1988), and the contribution of gum to the diet of the more frugivorous-insectivorous marmosets varies among species (Stevenson and Rylands 1988). Captive Cebuella and Callithrix species produce gouge holes in every material that they can manage to chew. Natural branches in the cage will not only provide the normal substrate for this important activity, but also direct the animals' attention away from materials that might damage their teeth. McGrew and others (1986) designed a sap feeder made of wooden doweling with holes drilled inside that was filled with gum arabic. Common marmosets quickly learned to excavate holes in this feeder to obtain gum. Tamarins lack the dentition to create exudate flows themselves, but they use exudate flows created by other animals.
Young monkeys, at about 4 weeks of age, begin to beg for solid food from animals that carry them. They obtain most of their food from other group members, which share food with them for several months. During this time, the youngsters seem to learn to recognize the group's food spectrum and to distinguish between wholesome and unwholesome foods. That experience might influence food selection and preferences later in life.
The natural diet marmosets and tamarins contains high concentrations of