Abstract:
Stable isotope analysis is a useful method to assess the spatial and temporal parameters integral to the niche ecology of marine mammals. Here, we implemented stable isotope values of sub-sampled regrowth whiskers and telemetry data from GPS/TDR loggers to investigate interspecific variation in the foraging ecology and of two congeneric fur seal species. Combining these methods enabled us to (1. deduce interspecific variation in isotopic niche widths (proxy for dietary niche width., and (2. establish interspecific variation in spatial niche utilization between Antarctic (Arctocephalus gazella. and Subantarctic (A. tropicalis. fur seals at three rookeries of different densities, with seasonal comparisons. We used 10 individuals from each of the three rookeries, with at least ten, ?12 mm whisker subsamples per individual. Isotopic values were calculated via the Standard Ellipse Area hence providing a measure of the isotopic niche utilized by each individual. We adapt an existing methodology, but this study will integrate temporal comparisons. Both fur seal species are income breeding marine mammals from Marion Island, in the southern Indian Ocean, although they invest differently in their annual breeding biology. Fur seals from high density rookeries exhibited broader isotopic niche widths due to competition. Variation of isotopic niche widths with respect to season was low. Variation in spatial and temporal niche utilisation persisted between rookeries of high and low densities which could be a sign of resource partitioning or other factors, hence requiring further analysis. - Abstract as displayed in the - Abstract booklet. The presentation on the day may differ from the - Abstract.
