Insights into the feeding habits of false killer whales (Pseudorca crassidens) in the Mexican Central Pacific

AbstractThe 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 ana-lyzed. Isotopic analyses were also run on muscle tissue from ten potential fish and squid prey spe-cies, 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 d13C (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 interac-tion 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.