tion to an individual animal, housing situation, and possible antecedent conditions that are at the root of the behavior. Alleviation of self-injurious behavior is frequently achieved through enrichment of the environment (Chamove and others 1984; see also the other discussions and references on this topic throughout this report) or introduction of the animal to compatible cagemates or social groups (Bernstein 1991; Line and others 1990b; Vermeer 1997; Williams and Abee 1988). If well-being cannot be achieved, euthanasia is a compassionate final option (AVMA 1993, AWIC 1990).

Group Housing. Group housing generally promotes behavioral health; primates typically exhibit a broad range of species-typical behavior when housed with other primates. But group housing increases risks of disease transmission, aggression, wounding, and food deprivation because of competition.

Various steps can be taken to minimize the risks. Food and water should be available from several locations to prevent individual animals from dominating a single source (Bloomsmith and others 1994; Maki and others 1989) and the food and water should be available in quantities sufficient to ensure that all animals receive an adequate ration. Also, shade, ancillary heat sources, and shelter should be provided so that some animals do not prohibit others from gaining access to critical resources. Likewise, environmental enrichment techniques should not incite aggressive competition over a device intended to enhance well-being (Maki and others 1989).

Disease transmission can be minimized by keeping social groups intact and introducing new animals only when necessary. (Some introductions of new animals are required in almost every colony for genetic diversity and replacement; it is critical that such introductions be handled carefully.) (See Chapter 2, "Social Companionship.") Equipment, such as transport cages, should either be dedicated to particular groups or be sanitized after use with a particular group of animals.

The risk of serious injuries caused by aggression to other animals is considerably greater in socially housed animals than in those living alone (Erwin 1979; Rolland 1991). No matter how carefully animals are selected for group living and no matter how well they have gotten along in the past, sudden outbreaks of aggression can occur and result in serious injuries (Ehardt and Bernstein 1986). Such spontaneous occurrences might be an important source of scientific information about the causes and consequences of social aggression. In any case, the facility staff has the obligation to monitor these events closely and to intervene in order to prevent serious injury to the participants. Decisions as to when and how to intervene require a considerable knowledge of the species, the particular social group, and effective techniques for dealing with serious aggression. Premature separation (e.g., before the social structure and dominance hierarchy are established) can invite renewed aggression when an animal is reintroduced.

Close observation of animals will often detect the onset of social instability long before aggression leads to injuries. For example, chasing, threatening, and



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