Habitat selection and influence on foraging success in female Australian fur seals

Abstract

Determining the factors influencing habitat selection and foraging success in top predators is crucial for understanding how these species may respond to environmental perturbations. For marine top predators, such factors have been documented in pelagic foragers, with habitat use and foraging success being linked to chlorophyll-a concentrations, sea surface temperature and light conditions. In contrast, little is known of the determinants in benthic marine predators. The Australian fur seal (Arctocephalus pusillus doriferus) has a breeding and foraging distribution largely restricted to Bass Strait, the shallow (max. depth 80 m) continental shelf region between the Australian mainland and Tasmania. The species forages almost exclusively on benthic prey and represents the greatest resident marine predator biomass in south-eastern Australia. The region is also one of the world’s fastest-warming marine areas and oceanographic changes are influencing shifts in prey distribution and abundance. In the present study, GPS-derived locations of benthic dives (n = 288,449) and dive behaviour metrics were used to determine seafloor habitat selection and factors influencing foraging success in 113 lactating adult females from Kanowna Island during the winters of 2006–2021. Individuals non-randomly selected foraging habitats comprised of deeper, steeper sloped, muddy-sandy areas with less gravel (P < 0.01). Foraging success was greatest in shallower rocky reefs (< 30 m) and deep areas (> 40 m) characterized by moderate presence of gravel (25–50%) and substantial rock composition (50–75%) on the seabed. These findings suggest that habitat use and foraging success in adult female Australian fur seals could be impacted by oceanographic changes that alter sea-floor characteristics and benthic communities.