allow for use of the full volume of a cage (Watson 1991). Species differ in the extent of manipulative curiosity, but all should be considered as potentially destructive. This should be taken into account in the design of cages, swings, puzzles, toys, and other enrichment devices. Cage height should consider the length of the animal's tail so that it will not touch the floor when the animal is sitting on a perch (NRC 1996). Cage furnishings should be routinely inspected for broken and hazardous items that need to be repaired or replaced. Some of the first demonstrations of visual curiosity in nonhuman primates were carried out in Old World monkeys (Butler 1954). Most enrichment devices described in Chapter 2 were designed with Old World monkeys in mind and serve well for enriching singly-housed rhesus monkeys (see also Line and others 1990a).

The dietary requirements for cercopithecine monkeys have been defined sufficiently to allow for successful breeding, growth and development, and maintenance (NRC 1978, 1996). If nutritional problems occur, they usually result from mismanagement of the diet, such as in its manufacture or storage. Appropriate handling of feed is described in the Guide for the Care and Use of Laboratory Animals (NRC 1996).

Cercopithecines can be successfully maintained solely on a fresh commercial feed, even though this is not recommended. Offering a variety of foods contributes to their psychological well-being (see discussion in Chapter 3). They will eat a wide variety of fruits, vegetables, and grains. Peanuts, popcorn, unsalted pretzels, dry cereal, shelled dry corn, millet seeds, and sunflower seeds can be used as treats; but potential contamination of natural food items should be considered, and reasonable caution is in order. Whereas adequate diets of wholesome foods obtained from the market can be achieved, it is far more convenient to ensure nutritional balance by using one of the many specially formulated commercial diets. Commercially available, nutritionally balanced food treats come in a variety of sizes, shapes, colors, flavors, and textures.

The colobines are more difficult to provide for nutritionally. Their diet should be heavily supplemented with green leafy vegetables. Some institutions have found that alfalfa is of benefit in caring for some colobines. A good commercially available diet is best to start with, but it will require considerable supplementation to maintain colobine monkeys.

Most species of macaques and baboons live in large troops consisting of numerous adults of both sexes. These social groups are often divided into smaller units called matrilines, which consist of mothers and their female offspring. Adult males are immigrants, unrelated to the females, that leave their natal troop