Sexual segregation in habitat use is smaller than expected in a highly dimorphic marine predator, the southern sea lion

Abstract

Sexual segregation in habitat use is widely reported in many taxa and can profoundly influence the distribution and behaviour of animals. However, our knowledge of the mechanisms driving sexual segregation is still in its infancy (particularly in marine taxa) and the influence of extrinsic factors in mediating the expression of sex differences in foraging behaviour is underdeveloped. Here, we combine data from biologging tags, with stable isotope analysis of vibrissae, to assess sexual segregation in southern sea lions (SSL) (Otaria flavescens) breeding at the Falkland Islands in the South Atlantic. We found evidence to support segregation, most notably in δ13C and δ15N values. However, in spite of extreme sexual size dimorphism and differing constraints related to female-only parental care, adult male and adult female SSL overlapped considerably in isotopic niches and foraging area, and shared similar foraging trip characteristics (such as distance and duration). This is in contrast to SSL breeding in Argentina, where prior studies report sexual differences in foraging locations and foraging trip characteristics. We posit that sexual segregation in SSL is influenced by habitat availability (defined here as the width of the Patagonian Shelf) and individual foraging preferences, rather than commonly invoked individual-based limiting factors per se.