Patterns of injury in zoo-housed spider monkeys: A problem with males?

Aggression among wild spider monkeys is most frequently reported to occur between the sexes, with adult males directing aggression towards adult females and the aggression is normally non-injurious. After two severe instances of aggression in the group of spider monkeys housed at Chester Zoo, we developed a questionnaire to investigate the frequency, direction and possible reasons for aggression in zoo-housed spider monkeys. We sent our questionnaire to 55 zoos worldwide and obtained records from 26 groups which yielded detailed accounts of 143 aggressive incidents: 56 events for the actors an 127 events for the targets of aggression. We found that zoo-housed spider monkeys are predominantly maintained in small social groups, with a single adult male, two adult females and their offspring. Of the aggression reported, 23.1% of incidents resulted in severe or lethal injuries. Adult males were the most frequent actors of aggression and accounted for 66.7% of incidents. Six cases of male-male aggression were lethal. The most striking pattern was that adult males directed aggression towards non-adult males more than any other age/sex category. The most frequently reported context of aggression was tension between adult and non-adult males. These findings contradict previous reports from wild spider monkeys where female-directed male aggression is most frequently reported. In light of our findings, we recommend that males form the core of the group and that females be relocated among groups to reflect the wild condition of male philopatry and female dispersal. In addition, enclosure design should allow opportunities for the monkeys to segregate themselves from other group members, simulating fission, which is a conflict management strategy for avoiding aggression in wild spider monkeys. (C) 2008 Elsevier B.V. All rights reserved.