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    Distribution of foraging by female Antarctic fur seals

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    I.L. Boyd, I.J. Staniland and A.R. Martin (United Kingdom)
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    The study examined the distribution of critical habitat for foraging by female Antarctic fur seals breeding at the island of South Georgia. Bathymetric features of the continental shelf around the island of South Georgia were an important indicator for the localisation of foraging. This pattern was consistent among years of different prey availability. Lactating females were constrained to forage mainly within 100 km of the location at which the offspring was being raised. When this constraint was removed at the end of lactation, females foraged to much greater ranges and dispersed to specific regions of the continental shelf east of Patagonia (>1000 km) and to the northern edge of the Antarctic pack ice (500 km). The empirical distribution of foraging during the breeding season was used to develop a function that described the foraging distribution for the whole breeding population of females. The result was consistent with past observations from ship-based surveys and it allowed estimation of the spatial impact of breeding female fur seals on krill at South Georgia. This suggested that, in extreme cases and assuming that krill influx is limited, female fur seals could eat most of the krill present in some regions where they forage intensively. However, mean consumption was about one-tenth of the mean density of krill.