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Keywords:

  • Aggression;
  • coping;
  • crowding;
  • chimpanzees;
  • Pan;
  • social behavior;
  • stress

Abstract

Among mammals there is usually an increased frequency of aggressive interactions when population density increases. Conducted at the Arnhem Zoo, the present study examined the effects of spatial crowding on social behavior. Observations were carried out during three winter and two summer periods, using six distinct behavioral categories as dependent variables. The hypothesis that the behavior of individual chimpanzees would be intensified under crowded conditions was examined. Only absolute grooming changes supported the “density-intensity” hypothesis. Aggression data exhibited only a slight increase. Apparently, advanced mammalian forms, such as chimpanzees and human beings, are able to cope with crowding-induced stress by engaging in alternatives to overt aggression.