Abstract: When otariid females leave the colony to forage at sea, pups stay in the rookery and gather in groups in which they rest and play. The major selective benefits of these groups are to develop social skills and physical abilities, as well as to reduce the risk of aggression by adults. The aim of this research was to study the aggregation behaviour in South American sea lion (Otaria flavescens) pups at Isla de Lobos, Uruguay, during the first 2 mo of life. During the breeding season of 2007 (January to March), from 0800 to 1800 h, instantaneous scan-samples were conducted every 2 h to record the number of groups in the area, number of pups per group, behavioral state, and location (land or sea). The number of groups increased during the first month, being positively correlated with the total number of pups in the area. A group size of two pups was most frequent (60.2%), followed by three pups (20.1%). Rest was the most frequent activity during most of the study period, and pup group activity did not vary over the weeks. The type of activity varied according to the time of day, with pups most active early in the morning, and also according to group size (the larger the group size, the higher the proportion of individuals resting in the group). The proportion of groups at sea increased with pup age, and interactions in a large group were more frequent at sea than on land. This research represents one of the first detailed analyses about aggregation behaviour in otariid pups.

Key Words: South American sea lion, Otaria flavescens, pinnipeds, pups, aggregation

Document Type: Research article

DOI: 10.1578/AM.35.1.2009.55

Page Numbers: 55-61