parenteral administration of alpha-tocopherol (vitamin E) to prevent vitamin E-responsive anemia lest clinical signs, including severe anemia and myopathy, develop. This can occur in animals whose baseline serum vitamin E levels appear normal (Meydani and others 1983; Sehgal and others 1980).

Social Behavior

Members of monogamous genera (Aotus, Callicebus, and Pithecia) have been successfully housed in captivity as mated pairs with offspring. Introducing adult strangers of the same sex is not always possible. Adult male night monkeys are aggressive toward one another; females can be housed together, but newly formed pairs should be observed to confirm compatibility. It is not known whether this applies to the other monogamous genera.

In monogamous species, it is sometimes possible to maintain offspring in the natal group until they reach sexual maturity. In cebids of polygamous genera, group size in captivity is limited mainly by space. Capuchins and squirrel monkeys have been maintained in groups containing 35 members or more with multiple adult males present. The introduction of new members to a group is usually problematic, especially if adults of the same sex are already resident. Considerable variation is to be expected. Given adequate space, woolly and spider monkeys can be kept in groups with multiple adult males. Adult male squirrel monkeys generally tolerate each other well in the absence of adult females, but fighting can occur if mixed-sex groups are formed at the start of the breeding season.

Many cebids readily accept an animal returned to the group after a week or more, and capuchins can be safely returned even after several months. Any major social reorganization that occurs in the absence of an individual animal complicates its return. Return of animals to large social groups appears to be easier if it occurs with only a portion of the home group present and if the small group is allowed to return to the main group a few minutes later. Spider monkeys are particularly excited by reintroductions, and such events warrant careful monitoring.

Attacks on infants occur occasionally in capuchins and in woolly, howler, and spider monkeys. The precursors of attacks are generally not evident, and animals behave tolerantly with infants under normal circumstances. It is thought that social instability can trigger attacks on infants.

As with the callitrichids, many cebids form polyspecific associations in the wild and are quite tolerant of extraspecifics. Squirrel monkey and capuchin associations are particularly common in the wild, but squirrel monkeys carry Herpes tamarinus and should be kept isolated from night monkeys and susceptible callitrichid species (Adams and others 1995). Mixed-species assemblages have otherwise been maintained in exhibits without adverse consequences.

Cebids use feces, urine, genital discharge, saliva, and secretions from specialized scent glands in the skin for the purpose of scentmarking. Sniffing and



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