Abstract: The false killer whale (Pseudorca crassidens) is a widely distributed odontocete, and some aspects of its basic biology, such as feeding patterns at different time scales, are not well known. Stable isotope values (δ15N and δ13C) from the skin of ten false killer whales belonging to two distinct groups (A and B) sampled in October 2012 in the Mexican Central Pacific (MCP) were analyzed. Isotopic analyses were also run on muscle tissue from ten potential fish and squid prey species, some of which were extracted from billfish stomachs. Isotopic results for false killer whales showed mean values of 16.3‰ (Group A) and 17.0‰ (Group B) for δ15N, and -14.8‰ for δ13C (both Groups A and B). Fish and squid isotopic values showed a trophic discrimination factor in relation to those of false killer whales of +3.3 to 4.0‰ for δ15N and +2.9‰ for δ13C. This suggests that these whales probably fed within the study area on these prey species or on other species with similar isotopic values. Through photographic data, we identified individuals of Group B in the same area 2 mo later (December 2012) when they were observed feeding on fishes. One false killer whale from Group A had a fragment of billfish beak embedded in its body, indicating an interaction between these two species. Results suggest that false killer whales may share the same type of food resource with billfish species such as the sailfish, an abundant species in the MCP area.
Key Words: false killer whale, Mexican Central Pacific, stable isotopes, potential prey, trophic similarity, billfish
Document Type: Research article
DOI: 10.1578/AM.40.4.2014.386
Page Numbers: 386-393

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