Foraging segregation by sex and age class in the Guadalupe fur seal from Guadalupe Island, Mexico

Abstract

AbstractA proper assessment of the foraging habits of the Guadalupe fur seal (GFS; Arctocephalus townsendi) is a priority to better understand its recovery, in which the potential for intraspecific competition for prey and space resources is expected to lead to segregation. This study aimed to determine the foraging habits of different sex and age classes. A total of 146 GFS fur samples was collected at Guadalupe Island, Mexico (2014–2020) for stable isotopes (δ13C and δ15N) analysis. Isotopic areas were created (SIBER package in R). Significant isotopic differences were observed between classes. Male (3.6‰2) and female (3.0‰2) juveniles had the largest isotopic areas due to a greater foraging dispersion. Adult females showed the lowest mean δ15N value (16.1‰ ± 0.5‰) due to foraging trips that are mostly performed towards high latitudes. Except for pups, adult and subadult males presented the highest mean δ15N (17.4‰ ± 0.4‰) and δ13C values (−17.0‰ ± 0.8‰) due to a possible higher trophic level and coastal foraging habits, whereas pups presented the highest mean δ15N value (17.6‰ ± 0.3‰) because of lactation, which reflects their mothers δ15N signal plus their own enrichment. Our findings suggest a segregation explained by differences in life history, energy requirements, and a possible strategy to avoid competition.