behavior could be harmful. In cases documented to result from early rearing conditions, the atypical behavior cannot be taken to mean that the animal is not being well cared for, given its early rearing experience.
Reducing stress is often considered the best way to promote the psychological well-being of captive primates, the assumption being that stress is the antithesis of well-being (Moberg 1985). However, stress occurs in many forms, both positive and negative, as noted by Selye (1974), who divided stressful stimuli into "eustress" and distress. It might be more useful to look for signs of distress in captive primates, such as chronic or excessive fear, grimacing, withdrawal, altered breathing, distress vocalizations, anorexia, or unusual postures (Morton and Griffiths 1985; NRC 1992).
The manner in which an animal adapts to environmental changes or brief environmental disruptions (e.g., cage-cleaning) can provide information about its psychological state (Mineka and Kihlstrom 1978; Mineka and others 1986). At issue are the appropriateness of the reaction, given the particular kind of disruption, and the time that it takes an animal to adjust to the temporary or new situation. One can examine adaptation in monkeys by evaluating their reactions to temporary but routine husbandry events, such as being removed from their home cage, or to more permanent events, such as a change in cage location.
The ability to adapt to change is a manifestation of a broader capability: to exhibit behavior appropriate to the environmental context. For example, it is expected that socially reared nonhuman primates will display a broad range of species-typical behavior and express the behavior patterns in relevant contexts. Such animals should interact in a socially competent, species-characteristic manner with cagemates (if present). They should not limit their movement through space to a small part of the environment or to a single repetitive pattern, such as pacing, but rather should display a variety of species-typical locomotor patterns.
Identification of species-typical patterns of behavior has depended heavily on studies of behavior in the natural environment. Some of the characteristics of wild populations that are thought to be relevant to captive primate well-being are the nature of social organization, mating system (e.g., monogamous), group size, group composition, spacing patterns, patterns of emigration and immigration, nature of habitat (e.g., open grassland or dense foliage), range of locomotor patterns (e.g., terrestrial or arboreal), food availability and dietary selection, sleeping places, nocturnality or diurnality, sedentary or mobile activity, feeding patterns, reproduction, age at sexual maturity, seasonality of breeding, parental care, communication, movement patterns, and normal postures of resting and sleeping. A plan for psychological well-being should take such characteristics into account. It should be noted, however, that there is a tremendous disparity in the amount of information available on the various species of primates held in captivity.
Even very closely related species (i.e., members of a genus) can differ substantially in behavior. For example, bonnet macaques (Macaca radiata) typically exhibit little intragroup aggression and show considerable group cohesion.