- lemur, most New World monkeys (cebids), many Old World monkeys, and the African apes—and has been used as a captive breeding strategy in some cases (Conlee and others 1996). But the details of the social organization of multimale groups vary widely. For example, in many groups, males disperse (e.g., rhesus monkeys); in others, the females transfer to other groups (e.g., chimpanzees); in some cases, both sexes disperse.
- Hand rearing. As a general rule, primates are good parents; however, as with other animals, including humans, some primates either reject their infants or encounter conditions that prevent proper infant care. Fostering or hand rearing is then possible, but providing for an infant's physical needs is far easier than providing for its social needs (Fritz and Fritz 1982, 1985). Substantial efforts will be require to provide the level of social stimulation necessary for the development of social skills in hand-reared animals. Frequent periods of interaction between young animals of similar age facilitate normal development, but continuous housing of hand-reared infants together is undesirable because it prolongs infantile behavior (Mason 1991) and might make the animals more susceptible to disease through alterations of the immune system (Gust and others 1992). Although some animals can be successfully placed with foster mothers of their own or closely-related species, many rejected infants are raised by humans. It is seldom possible under these circumstances to produce an infant with the same frequency and intensity of social contact and stimulation as provided by the natural mother and group, but every effort should be made to maximize the time that such infants are held, carried, and allowed to engage in social interactions. Inanimate surrogates and occasional contact with others will not ensure normal social development. (For additional reading on hand rearing, see Fritz and Howell 1993a; Fritz and others 1992a; Maki and others 1993; Meder 1985; O'Neill and others 1991; Reisen 1971.)
Appropriately trained and observant personnel are essential to maintaining primates in captivity. The caregivers should be knowledgeable not only about general husbandry procedures but also about the specific behavioral characteristics of the primate species for which they are responsible. Because of their contact with the animals in their care, they are often in the best position to note signs of illness, injury, or distress. Human interactions with primates can al have a profound impact on both physical and behavioral well-being (Baker 1997; Bayne and others 1993a; Miller and others 1986). For example, personnel can engage in activity that communicates negative messages to the animals, such as macaques and baboons, which can interpret a direct stare as a threat. Conversely, personnel can communicate messages that reduce animal stress, such as lip-smacking at chimpanzees or macaques.
For an enhancement program to succeed, those responsible for implementing