others 1993). The cage sizes for particular species are currently determined by the typical weight of species members. Such an approach fails to provide for performance standards based on typical postures or locomotor expression, such as stride length. The extent to which performance standards can be translated into appropriate cages and housing depends on thorough study of species, age, and sex differences. It is important to specify cage configurations, in addition to absolute size. Other kinds of information will also be needed. Perch height should be examined in the context of both body conformation and tail length. Information on species-typical resting patterns can be relevant, inasmuch as some animals sit and others sprawl with arms and legs extended. Various stride characteristics should be identified. For example, if an animal travels horizontally with a quadrupedal gait, how long is each normal stride? For arm swinging species, what is the arm span in travel (as opposed to maximal reach), and what height is necessary for the feet to clear the ground? How far apart should supports be for vertical clingers and leapers? Those basic measures should be characterized during development for both sexes of each species.

According to the experience of many primate-colony managers, the vertical dimensions of housing affect the well-being of some species. Under natural conditions, many primates spend much of their lives aboveground and escape upward to avoid terrestrial threats. Therefore, these animals might perceive the presence of humans above them as particularly threatening. In addition, such environmental variables as lighting, temperature, and airflow are likely to be affected by height, and these in turn could influence an animal's physiological state. Clarification of the contribution of such factors to well-being is needed. New cage designs should be developed to foster the humane capture of primates that are maintained singly or in groups. Cages should facilitate the regrouping of animals, their transfer between cages, and their access to different cages. Different kinds of materials should be examined that might provide for optimal use of limited intracage space by particular species and accommodate species-typical behaviors, such as marking, leaping, and chewing. Optimal use of available cage space might well depend more on the placement of perches, platforms, moving and stationary supports, and refuges than on cage size itself.

Social Groups

Primates are noted for their social behavior and proclivities. Although individual caging of primates might be required by protocols of approved studies or by reason of the social incompetence or health of a given animal, group caging is often more appropriate in light of the social needs of a species. Field data from various species have revealed long-term bonding relationships between parent and offspring, siblings, and others. Several factors should be studied to understand more fully the impact of social housing on psychological well-being. These include group formation, group composition, group size, and group stability. It is

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