Colony-based foraging segregation by Antarctic fur seals at the Kerguelen Archipelago

The foraging behaviour of conspecific female Antarctic fur seals (AFS) was compared simultaneously at 2 breeding colonies at Îles Kerguelen (S Indian Ocean). A remnant colony at Îles Nuageuses (IN) thought to have escaped sealing is hypothesized to be the source of increasing fur seal numbers at Cap Noir (CN) on the Kerguelen mainland. Inter-annual variability in foraging areas is known to occur in response to local oceanographic changes at CN. Given the distance between the 2 sites (∼160 km), we hypothesize that seals from the 2 colonies may show spatial segregation in foraging due to variability in local prey resource availability, although the transfer of foraging knowledge between sites via emigration may override such behaviour. The foraging zones, diving activity, diet and foraging success of seals were compared between sites using satellite telemetry, dive recorders and faecal analysis. No evidence of spatial foraging overlap was observed, with seals from IN conducting longer foraging trips, typified by a longer initial transit phase, than CN seals, which spent less time diving at night and dived more deeply. Pups nevertheless received higher absolute and daily energy delivery rates at IN. Diet was superficially similar at ∼98 % myctophid consumption; however, IN seals favoured the high-energy Gymnoscopelus nicholsi, indicating that local heterogeneity in marine resources likely influences the foraging zone choice of AFS. Finally, distribution patterns of 54 female AFS tracked during summer months from 1998 to 2006 reveal the importance of both on-shelf (<500 m) and shelf-break regions as foraging habitat. The core foraging area for CN in all years (10 400 km 2) was small (∼10 % of total foraging space); however, time spent in this region alone totaled 38 %. The likelihood of spatial overlap in foraging range is higher on the east coast of Kerguelen. © Inter-Research 2008.