What is it about?
Why are California sea lions thriving in some places but declining in others? Our research found that differences in diet quality—the nutritional value and diversity of their prey—don’t fully explain these contrasting trends. Instead, population dynamics in the Channel Islands and the Gulf of California are shaped by distinct local ecological conditions, it's like comparing apples and oranges. Even within the Gulf of California, each region is so unique that sea lions experience different population patterns depending on where they live.
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Photo by Samuel Scrimshaw on Unsplash
Why is it important?
Although California sea lions (Zalophus californianus) as a species show an increasing trend and are of "Least Concern" according to the IUCN, sea lion populations in Mexico are under "special protection" due to their declining population trends. Our findings show that these regional population trends are driven by complex ecological factors beyond diet, underscoring the importance of considering environmental heterogeneity when investigating sea lion population dynamics in the Gulf of California, especially under a changing climate.
Perspectives
Sea lions in the Channel Islands are influenced by broad-scale dynamics, such as climate and prey availability in the California Current System. In contrast, the Gulf of California presents a more complex picture, where environmental heterogeneity at regional and local scales can strongly shape population dynamics. For instance, the trends at each rookery may be driven by a combination of factors, including prey availability, bathymetry, foraging strategies, human impacts, and even the size of the local sea lion population. Recognizing the appropriate scale of study—focusing on smaller, regional populations rather than treating the Gulf as a single system—is crucial for understanding the drivers of population dynamics in the Northern, Central, and Southern Gulf of California.
Ana Lucia Pozas Franco
University of British Columbia
Read the Original
This page is a summary of: Environmental heterogeneity plays a bigger role than diet quality in driving divergent California sea lion population trends, PLOS One, November 2025, PLOS,
DOI: 10.1371/journal.pone.0324108.
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