Foraging Resource Partitioning in the California Sea Lion (<i>Zalophus californianus</i>) from the Southwestern Gulf of California
California sea lion (CSL, <i>Zalophus californianus</i>) abundance has declined in different localities across this species’ Mexican distribution. However, Los Islotes rookery in the southwestern Gulf of California (GoC) deviates from this pattern. It is vital to gather ecological knowle...
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| Main Authors: | , , |
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| Format: | Article |
| Language: | English |
| Published: |
MDPI AG
2025-02-01
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| Series: | Diversity |
| Subjects: | |
| Online Access: | https://www.mdpi.com/1424-2818/17/3/166 |
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| Summary: | California sea lion (CSL, <i>Zalophus californianus</i>) abundance has declined in different localities across this species’ Mexican distribution. However, Los Islotes rookery in the southwestern Gulf of California (GoC) deviates from this pattern. It is vital to gather ecological knowledge of this CSL settlement and its surroundings to better understand its population in the GoC. This study aimed to determine the foraging habits of different CSL sex and age classes. Sixty-five CSL samples were collected in Los Islotes and its surroundings for stable isotope analysis (δ<sup>13</sup>C and δ<sup>15</sup>N). The data were analyzed using a hierarchical Bayesian model, and isotopic areas were estimated using the SIBER package in R. Our findings evidenced resource partitioning. Adult females had lower δ<sup>15</sup>N values than most classes, reflecting the regional <sup>15</sup>N-enrichment of the GoC. Conversely, subadult males showed low δ<sup>15</sup>N values, carrying foraging information from the <sup>15</sup>N-depleted Pacific Ocean into the GoC. Adult males presented the highest δ<sup>15</sup>N values (after pups), suggesting a higher trophic position than adult females and values corresponding to the GoC. Moreover, juveniles had the most negative δ<sup>13</sup>C values and the largest isotopic areas, indicating offshore foraging habits and a mixed consumption of maternal milk and their first prey. Pups showed the highest mean δ<sup>15</sup>N value due to maternal milk consumption, reflecting the mother’s δ<sup>15</sup>N value and their enrichment. Our findings suggest that segregation is explained by unique life history traits and a possible strategy to avoid potential competition |
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| ISSN: | 1424-2818 |