Foraging ecology of the olive ridley sea turtle (Lepidochelys olivacea) from the Mexican Central Pacific based on stable isotopes

Knowledge regarding the trophic ecology, including the feeding habits of olive ridley sea turtles (Lepidochelys olivacea), is scarce. Although few investigations have been carried out, some results are contradictory. We described several foraging aspects of this sea turtle species in the Mexican Central Pacific (MCP) using stable isotopes of carbon (delta C-13) and nitrogen (delta N-15). Data were analyzed by sex, size classes (adult/subadult), season (rainy/dry), and location (coastal/oceanic). Surveys were conducted during February 2012-June 2014. A total of 120 olive ridley sea turtles were captured, of which 86 were adults and 32 subadults; 40 were females and 46 males, while the sex of two adult individuals was unidentified. Descriptive statistics and Bayesian analyses of delta C-13 and delta N-15 values were performed. A similar isotopic niche width (delta N-15) between males and females was found; while it was wider in adults compared to subadults. A wide delta C-13 range by sex (females) and by size (adults) was evidenced. Values of delta N-15 differed significantly, with lower values observed during rainy seasons. There were no significant differences in delta C-13 or delta N-15 between turtles captured in the coastal and oceanic areas. We infer that olive ridley sea turtle feeding areas occur in coastal areas due to the occurrence of upwellings that increases primary productivity; and during the rainy season, most sea turtles fed in coastal and intermediate areas, as oligotrophic characteristics resulted in turtles increasing their feeding range. The isotopic difference between olive ridley sea turtles and the items that were sampled in the region, suggests that crustaceans, cnidarians, and small pelagic fishes are potential prey of these turtles, which support the argument that these are opportunistic foragers. The present study highlights the importance of the MCP region for the ecology and conservation of olive ridley sea turtles, which seem to feed in the region. (C)& nbsp;2022 Elsevier B.V. All rights reserved.

Automated summary

This study investigated the foraging aspects of olive ridley sea turtles in the Mexican Central Pacific using stable isotopes of carbon and nitrogen. The results showed a wider isotopic niche width in adult turtles compared to subadults and an expanded feeding range during the rainy season. The study highlights the ecological importance of the MCP region for olive ridley sea turtles and emphasizes the need for conservation efforts.