Ecological niche segregation among five toothed whale species off the NW Iberian Peninsula using ecological tracers as multi-approach

This study aims to assess niche segregation among the five main toothed whales that frequent the NW Iberian Peninsula waters: the common dolphin, the harbour porpoise, the bottlenose dolphin, the striped dolphin and the long-finned pilot whale. We used cadmium (Cd) and stable isotope ratios (delta C-13 and delta N-15) as ecological tracers to assess degree of segregation in diet/trophic level and in foraging habitat, over various time-scales. delta C-13 values highlighted different habitats, while Cd concentrations highlighted feeding differences between oceanic and neritic species. Moreover, delta N-15 values suggest different trophic levels of prey targeted within oceanic and neritic species. Hence, results revealed long-term ecological segregation among five toothed whales that coexist in the NWIP and demonstrated the ability of ecological tracers to discriminate ecological niches among closely related species.