Sociality and asociality in white-nosed coatis (Nasua narica): foraging costs and benefits

Abstract

White-nosed coatis maintain a social structure of female-bonded groups (called bands) and solitary males. I examined the foraging success of social and solitary individuals and the possible importance of intraspecific foraging competition in maintaining the social system, particularly in the associated context of sexual dimorphism. The study population was almost entirely frugivorous-insectivorous. Invertebrate foraging success did not differ between solitary males and band members, although solitary adult females were more successful than those in bands. Fruit foraging success of solitary adult males was generally greater than that of band members, although this result varied with patch size and depended on the age class of examined band members. Small food patches showed the greatest differential between the foraging success of solitary males and band members. Agonistic interactions between males and bands often occurred at fruiting trees, and foraging group size was important in determining the outcome of these events. Larger males were able to displace solitary females and small foraging groups from fruit patches. In turn, larger groups of smaller females displaced solitary males. Male-male agonism at fruit patches was also common, with larger, older males usually winning agonistic interactions. These findings suggest that coati social structure directly influences foraging, and I therefore hypothesize that the coati social system is maintained (in part) by body size sexual dimorphism interacting with reliance on patchy defendable foods. Female group living allows increased access to patchy resources that are otherwise unavailable due to small body size relative to competing males. In contrast, larger males are able to access food patches without living in groups that might increase foraging competition.[Behav Ecol 7: 254-263 (1996)]