Nonhuman primates in captivity have been maintained in varied housing conditions. Animals have been housed for many years in research facilities in individual cages that can be easily sanitized and placed in climate-controlled rooms. Indoor-outdoor runs have been used as primary housing, usually with the indoor portion engineered to protect the animals from environmental extremes (NRC 1996). Heavy-wire units originally built to store corn and often referred to as corn cribs and corrals with areas of 0.1–3.0 hectares (0.2–7.4 acres) have been used as outdoor housing. Some corrals contain structures to protect the animals from the elements; others are connected to structures that provide shelter and are used to capture the animals. Nonhuman primates have also been maintained on islands, some with areas of over 175 hectares (430 acres). Each form of housing has advantages and disadvantages.
The acceptable temperature range for primates adapted to the outdoors varies greatly. Some species, such as savanna baboons, when properly acclimated can tolerate temperatures from near freezing to over 39°C (102.2°F), whereas other species, such as pygmy marmosets, can survive only in relatively narrow temperature ranges. Regardless, primates housed outdoors should be protected from environmental extremes in ways that are appropriate to their species, age, disease status, and acclimatization. Indoor-housing temperature fluctuations should be kept within the range of 18–29°C (64–84°F) (NRC 1996; see Chapters 5–9 for species-specific information).
Efforts to provide cage size recommendations according to animal size have been frustrated by the enormous diversity of nonhuman primate lifestyles and locomotor activities. No single factor, such as body weight or size, is sufficient to specify cage designs for captive primates. A matrix of factors should be considered, including species-typical behavior, postures, locomotor activity, age of the animals, required duration of caging, and number and sex of animals to be housed in each cage. However, housing should allow the animals to exist in a state of physical and psychological well-being.
Cages should be designed to permit normal postures and locomotor activity. When not stressful (e.g., with breeding pairs of marmosets), walls should be as open as possible—e.g., consisting of mesh, glass or clear plastic, or bars—because the ability to monitor their environment visually is very important to some primates. A nest box or shelter with opaque walls will allow an animal to "hide" when it wants to be out of direct view. Cage design should minimize discomfort and risk of injury to the animals. For example, some species have anatomical features, such as long tails, that might require a taller cage than other species of the same body weight. An animal maintained for an extended period might require a larger cage so that it can partake of its normal locomotor activity. Smaller quarters might be justified case by case for quarantine, veterinary, or experimental requirements.