Adoption of infant howling monkeys (Alouatta palliata).

During 3 years of continuous field observations on mantled howlers (Alouatta palliata Gray) in Costa Rica we observed five infants without mothers in the main study group. Four of these infants solicited care and two were adopted (one permanently, one temporarily) by lactating females. The other two were carried but not adopted. The fifth neither solicited nor received care. An infant must solicit care to receive care, and female howlers apparently can suckle more than one infant at a time.