Natural and anthropogenic factors associated with the distribution of South American sea lion along the Atlantic coast

Abstract

The aim of this work was to analyse those characteristics of the Atlantic coast that are associated with distribution, abundance and breeding activity of Otaria flavescens at three ecological scales. We followed a research strategy that consists in looking at the variables that are associated with the pattern of distribution at regional and landscape scales, instead of following local population in time. We used bibliographic data of censuses carried out between 1946 and 1997 and a Geographic Information System to integrate information proceeding from censuses and different environmental variables. At a regional scale we found that the distribution of breeding colonies did not vary in the period of time analysed and was associated with the pattern of occupation of the coast and the tide width. There was a significant decrease in abundance between 1946 and 1997. In ‘north-central Patagonia’, the segment of coast with the highest number of sea lions in Argentina, distribution of colonies was associated with islands availability and negatively correlated with places were anthropogenic disturbance was high. At a local scale, breeding colonies were positive associated with slight slope coasts and negatively associated to rocky beaches. We identify those characteristics of the coast associated with distribution of breeding colonies of O. flavescens, which operate at different ecological and temporal scales.