Habitat use and diving behaviour of male Australian fur seals

Marine predators play an important role in the structure and function of the ecosystems they inhabit. Knowing where marine predators forage and how individual strategies vary, therefore, has important implications for our understanding of ecosystem processes as well as species management and conservation. However, within fur seals and sea lions, knowledge of foraging ecology is typically biased towards adult females, and data on other critical life history stages are often lacking. This study investigated the habitat use and dive behaviour of 16 male Australian fur seals Arctocephalus pusillus doriferus at Kanowna Island (3° 10' S, 146° 18' E) in northern Bass Strait, southeastern Australia during 2013 and 2014. Winter behaviour (inferred from location and dive data) indicated that male Australian fur seals, like females, were predominantly benthic foragers who had a restricted foraging range limited to the shallow continental shelf of Bass Strait (60 to 80 m). However, in late spring and summer, some males travelled away from central Bass Strait and foraged in deeper waters ( > 200 m) along the edge of the continental shelf. These movements occurred immediately prior to the breeding season, suggesting continental shelf slope waters are also important habitat for male Australian fur seals at a time of great nutritional importance. Strong inter- and intra-individual variation in diel diving patterns were also apparent, with little spatial overlap in the core foraging range of each diel strategy (diurnal, mixed and nocturnal). This variation may reflect individuals using alternate strategies to target specific prey in different areas of Bass Strait, or may be due to competitive exclusion by conspecifics.