EFFECT OF GROUP-SIZE ON VIGILANCE WHILE DRINKING IN THE COATI, NASUA-NARICA IN COSTA-RICA

Vigilance and the duration of drinking bouts at a waterhole in Palo Verde, Costa Rica were examined in coatis, Nasua narica. Coatis came to drink in groups of one to 13. Only males came alone to the waterhole. Mean length of drinking bouts decreased with successive bouts, and most coatis had one to four drinking bouts per visit to the waterhole. Length of all drinking bouts increased with group size, and vigilance decreased as group size increased. Larger groups remained at the waterhole longer than smaller groups. The results of this study suggest that waterholes are particularly dangerous places because their location is known to predators and coati are required to come to them. Thus, being in a large group is advantageous at a waterhole where vigilance time per individual can be less in larger compared with smaller groups, and there are more eyes to watch for predators. © 1992 The Association for the Study of Animal Behaviour.