Responding to Human Influence: Southern Sea Lion Males Adapt to Harbor Habitats

Male-only hauling grounds occur in close association to breeding colonies in several otariids. The occasional use of human-built infrastructure by these groups is also common. We observed permanent male aggregations of southern sea lions, Otaria flavescens, in urban contexts, such as two of the main fishing harbors in Argentina and investigated how they changed over 35 years. These haul-outs are located approximately 700 km from Uruguayan and northern Patagonian breeding grounds. Males in urban colonies have functional connections with both populations. A predictable pattern of dispersion during the breeding season, returning for winter, indicate site fidelity. Harbor habitats present ever changing stimuli, threats and challenges to habituated sea lions. Sequential, rapid and spontaneous changes in the location of the aggregations may be a response to quick learning and socially transmitted knowledge. Food provision via consumption of fish offal—complemented with natural foraging—provide support to these aggregations over prolonged periods. The presence of hundreds of sea lions in harbors represents a management challenge. Fidelity to resting areas and rapid habituation to human presence makes it difficult to design strategies that can deter sea lions from intensive use of critical sectors of port activity. Interaction with fishing gear results in frequent entanglements. The risk of transmission of diseases from and to dogs and other domestic animals is a major potential problem for individuals in unnatural aggregations.