Infanticide by Adult and Subadult Males in Free-ranging Red Howler Monkeys, Alouatta seniculus, in Venezuela

After 15 males invaded troops of wild red howler monkeys {Alouatta seniculus) present in Venezuela during the period from Apr. 1989 to May 1991, five infant killings and eight infant disappearances occurred. Among the eight groups that were invaded, 10 infants of less than 3 mo old and three of over 5 mo old were killed either by the adult or subadult males, or disappeared. However, on the five occasions of invasion, none of the nine infants were killed. In two other groups, there were no infants present at the time of invasion. It was also noted that no infant of kin of the invading males was killed. At least six of the females that had lost their infant during such invasion subsequently copulated both with the invader as with the original resident male. In one case, a female copulated with the resident male of a neighbouring group. In the four cases of subadult males committing infanticide there was no immediate sexual access to the females. The data presented here are inconsistent with the reproductive sexual-advantage hypothesis, but consistent with the hypothesis concerning food competition. Corresponding author: Govindasamy AGORAMOORTHY, Department of Biology, National Sun Yat-sen University, Kaohsiung 80424, Taiwan (ROC).