When social separation or isolation is proposed as a research manipulation, several issues 
should be considered. These include the species and age of the animal; its ability to maintain 
itself independently; the frequency and duration of the separations to be experienced; and the 
evaluation procedures used by the investigator. The future requirements of the animals 
should also be considered. 
The oversight of research involving social factors is an especially difficult area of 
consideration for IACUCs for several reasons. Opinions differ on the social needs of various 
species. Definitions of terms such as “stress" and "well-being” are vague. And the task of 
balancing research goals against evolving standards of animal care is precarious. A key factor 
in any consideration of social variables is the known predilection of all organisms to adapt 
and cope with changing environmental conditions. Many investigators have documented 
changes in behavior that occur with changes in social or physical stimuli in the caged animal's 
environment (e.g., Evans et al., 1989; Hubrecht, 1995), but there are few instances in which 
the animal's new "behavioral budget" is clearly an advance in health outcome. Although this 
section emphasizes research methods, the influence of social factors in husbandry will be 
described briefly because these factors influence behavior and have become a standard 
component of husbandry practices for some species (ILAR, 1996, pp. 37-38). Bayne and 
Novak (1998) provide an excellent review of variables that influence behavioral pathology in 
captive nonhuman primates. 
BEHAVIORAL IMPLICATIONS OF MANIPULATING 
SOCIAL VARIABLES 
SOCIABILITY OF THE SPECIES 
Early research suggested that some animals (many primates and rodents) may have an innate 
“gregarious" tendency that predisposes them toward social living, whereas others (adult male 
primates and some carnivores) are more inclined to live solitary lives. Human experience and 
further animal studies show, though, that the tendency for or against sociality is influenced 
by early rearing conditions. Group-rearing of rodents or macaques in infancy may foster a 
preference for social housing, whereas the same species may find social living aversive if 
derived from a less social rearing environment. The full extent to which “social needs" can be 
modified by the rearing environment remains an empirical question. 
GROUP FORMATION AND INTRUDER PARADIGMS 
Routine husbandry will at times require the formation of new social relationships, as 
individual animals are retired from the experiment and new animals replace them. 
Incompatible pairs or groups should be separated and more appropriate companions found, 
when available. When aggression is not the focus of the research, it is especially important in 
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