physical and behavioral norms for an animal, in addition to evidence of illness or injury. Lethargy in a normally active animal might be the only readily notable indication of a life-threatening condition. Unless a special diet has been prescribed to control excessive weight, caregivers should be certain that at least some food remains each day. Old food should be removed when new food is provided. It is especially important that caregivers ensure daily that all watering systems are functioning. If any animal shows less interest than usual in eating when fresh food is provided, that should be noted. A special effort should be made to check each animal in a social group, although this might not always be possible in some situations, such as in island colonies. The minimal requirements for daily care include the provision of food that is adequate in nutritional value and presented in a form that is easily consumed, the availability of potable water at all times during normal housing, and cleaning of cages in a manner and with a frequency that ensure control of disease (NRC 1996).
A balanced diet is essential to maintain the physical health of primates. The dietary requirements of a few species of primates have been defined (Knapka and others 1995; NRC 1978) and several commercial manufacturers produce dry biscuits or moist products that meet these requirements. Some primates require a diet relatively high in protein, although excessive protein might lead to kidney problems in some night monkeys (Aotus). Diets can be purchased with different percentages of protein (15–25%) as appropriate to the colony. No diet can be considered appropriate for all primates. However, vitamin C is an essential component of the primate diet. Vitamin C added to commercial feed loses potency rather quickly, depending on storage conditions. If feed is refrigerated, the vitamin will be preserved longer, but commercial feed generally should be used within 90 days of milling. Supplementation with fruits that contain vitamin C provides food variety. Primates also require vitamin D in their diets, especially when housed indoors, and New World primates require vitamin D3 supplementation (Bennett and others 1995). Because primates have diverse requirements for nutritional well-being, it might be difficult to form a balanced diet with only unprocessed natural foods. Most primates are omnivorous and cannot exist on a diet consisting only of grains, fruits, and vegetables.
All primates require regular access to water. Open watering pans or bowls can be used, but they are readily contaminated with feces, urine, and debris. If water is piped to primates housed outside, care should be taken to prevent freezing or excessive heating by the sun. Whereas most primates rapidly learn to use automatic watering devices, new animals need to learn how to use them.
Feeding can be used to provide positive behavioral stimulation as a means of enhancing primate well-being (Bayne and others 1992b; Fajzi and others 1989; NIH 1991). Variations in feeding strategies are particularly appealing because