Resumen del producto

¹ Instituto Politécnico Nacional, Centro Interdisciplinario de Ciencias Marinas

A large amount of knowledge has been gathered in relation to male California sea lions’ (Zalophus californianus) migration from colonies in USA to higher latitudes. However there is scarce information of in this regard for colonies in Mexico. We recorded the abundance of subadult males throughout 37 monthly (2012-2016) counts in the southernmost breeding colony (Los Islotes, La Paz Bay in the southern Gulf of California) of the species, and we analyzed stable isotopes (d15N and d13C) in fur of stranded subadults in La Paz Bay, and resident females from Los Islotes and the San Benito Archipelago, in the Mexican Pacific (2013-2015). We revealed an update on the subadult males’ seasonality, providing a similar pattern as the one found in 1979-1981, but recording a larger number of individuals, as a result of the population growth of the species over the last four decades. Isotopic results suggested a migratory origin of subadult males sampled in our study area, especially in relation to a larger isotopic niche, because of their wider dispersion relative to resident adult females from Los Islotes and San Benito, and 15N depleted values in subadults (relative to females from Los Islotes) that are typical of the Northeastern Pacific instead of the Gulf of California (15N-eriched baseline). Hence, we hypothesized the entrance of subadult males from the Mexican Pacific into the Gulf of California. These findings are a contribution to what is known about Zalophus californianus in its southernmost distribution margin, especially in terms of males’ dispersion.

Palabras clave: sea lion; migration; colonies

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