licking urine, scent marks, or the bodies of conspecifics are common in all species. Techniques vary, but urine washing and distribution of urine over parts of the body occur in various forms in most genera. Titi, woolly, and spider monkeys distribute saliva over parts of the body, including a sternal gland on the chest. Capuchins and uacaris rub plants and other items in their environment into their fur. Chemical signals might identify an individual animal's sex and play important roles in reproductive behavior, aggressive interactions, and other kinds of behaviors. Sanitation procedures should take into consideration the possible importance of odors for the cage inhabitants. The presence of odors in a monkey run should not be taken to mean that sanitation is inadequate (Williams and Bernstein 1995; see also "Sanitation" in Chapter 3).
Age at reproductive maturity ranges from 2 years in Saimiri, Callicebus, and Pithecia to 5–6 years in Lagothrix, Ateles, and Cebus. Members of some genera breed seasonally (e.g., Saimiri and Cacajao); members of others (such as Cebus) do not. In some genera, females exhibit marked proceptive behavior (i.e., they seek out and actively solicit a male) and mate preferences. Duration of gestation in cebids ranges from about 4.5 months (in Aotus) to 7.5 months (in Ateles) (Napier and Napier 1985).
Single births predominate. Infants can cling unaided from birth but do not locomote independently for several weeks to several months; they ride dorsally soon after birth (the precise age at which dorsal riding begins varies with the genus, from birth to about 2 months). However, in some genera (capuchins, woolly monkeys, and spider monkeys), mothers often cradle infants ventrally for extended periods and assist a newborn infant in clinging to the ventrum if the mother moves while it is in a ventral position.
In the monogamous genera (night monkeys and titis; there is no information on this point for sakis), infants are routinely carried by fathers when they are not nursing. In capuchins and squirrel monkeys, infants can be carried by adults and juveniles other than the mother (Fragaszy and others 1991; Williams and others 1994). The period of infant dependence varies among genera; in the larger forms (e.g., Ateles), infants can remain on the mother and nurse for up to 2 years. Nursing periods among cebids are generally longer than is typical of Old World monkeys.
In species in which both parents are involved in infant care (titi, night, and owl monkeys), rejection of an infant by either parent might require human intervention. A male titi can provide adequate care for an infant rejected by its mother, but the infant will require hand feeding. Male titis can be box-trained and exhibit little protest when an infant is gently removed, fed, and returned. When a father rejects an infant, the mother alone often becomes agitated with the