Within-group spatial position in ring-tailed coatis (Nasua nasua): Balancing predation, feeding success, and social competition

Several factors shape the within-group spatial position preferences of animals, most notably; predation, dominance rank, food abundance and depletion time, and prior knowledge of food location. Individuals are predicted to choose spatial positions which maximize their personal fitness, and various factors can affect the costs and benefits of these spatial positions. The total summed spatial position preferences of all group members determines the group geometry which has a major effect on the type and degree of feeding competition and thus impacts social structure. I first present a qualitative model predicting where individuals should locate themselves in groups. To test this model, I studied groups of wild ring-tailed coatis in Iguazu, Argentina.;Survivorship rates for coatis in Iguazu were high, and individuals often lived in groups with many close relatives. These coatis had an odd dominance structure in which small juvenile coatis would regularly attack older individuals and win agonistic interactions during feeding. This system was likely driven by a combination of fast life histories which led juveniles to value food more than older individuals, close genetic relatedness between group members, and adult female support of juveniles. This agonistic behavior of juveniles was likely a form of extreme juvenile tolerance rather than juvenile dominance in the traditional sense.;Coatis almost always discovered food by olfaction. Individuals at the front of the group found far more experimental food plots than individuals in other spatial positions, but were almost always joined by other group members. Juveniles were found at the front edge of the group more than all other age/sex classes. This led to higher fruit foraging success, especially on pindo fruit trees. At the same time, these juveniles were essentially ignoring the increased predation threat from being at front of the group. Subadults were located in areas to best avoid feeding competition and receiving aggression from adult females. The spatial position preferences shown by coatis were different from that predicted, but still conformed to the essential principles discussed in the model.