Developmental and Comparative Aspects of Social Play of Mantled Howling Monkeys in Costa Rica

AbstractThe social play of infant and juvenile mantled howling monkeys in Costa Rica was studied via focal sampling (529.2 h) of known individuals of known age over a 22-month period. Observations of adult males (291.2 h of focal samples), done over portions of 3 calendar years, provided supplemental data for the social play of adults. Developmental patterns of play are presented, and are compared with data available for other mantled howlers, other sites, and other species of howlers. Social play by infants and juveniles occurred at the rate of .56 bouts/h, represented 5.79% of the total focal observation time, and bouts had a mean duration of 6.19 minutes. Play by an adult male occurred at the rate of .03 bouts/h (.007/h for all 4 adult males combined), represented 0.24% of his total focal time, and had a mean duration of 5.0 minutes. Ontogenetically, social play began in the 8th week of life. Infants' rates of play and percentage of time spent in play increased from the I1 stage through the I3 stage, then decreased into the juvenile period (> 1 year of age). Mean durations of play bouts increased through the 3 infant stages, then decreased slightly in the J1 stage. The occurrence ofplay groups (3 or more individuals) increased through the infant and juvenile stages. As infants aged, a larger percentage of bouts occurred further from the infants' and juveniles' mothers. With respect to social variables, no overall developmental pattern was evident for playing with an older or younger partner, or a partner that was the offspring of a mother ranked higher or lower than one's own mother; different age classes showed different patterns. When an older sibling was available as a play partner, no preference for this relative was shown. I3's had the highest number of different play partners. Immature howlers played predominantly with other immatures (93% of their interactions). The behaviours observed during play were similar to those reported for other howlers; the behaviours emitted by an adult male were similar to those of the juvenile partner, as was the style and intensity of play. The social play of these mantled howlers is viewed with respect to social, demographic, and ecological variables. The play of howlers is both facilitated and constrained by these variables.