Male California Sea Lions are Becoming Bigger and Better Fighters as Their Population Rebounds
Published:09 May2023    Source:Cell Press

California sea lions have managed to maintain -- and, in the case of males, increase -- their average body size as their population grows and competition for food becomes fiercer. This is in contrast to other marine mammals, whose average body size tends to decrease as their numbers increase.

Researchers report April 27 in the journal Current Biology that sexual selection was a strong driving force for males to grow bigger and to strengthen muscles in their neck and jaw that help them fight for mates. Both male and female sea lions evaded food shortages by diversifying their diets and, in some cases, foraging further from the shore.
Overall, the researchers found that male sea lions have increased in size, while female sea lion size has remained stable. This sex difference is probably due to the fact that size matters for male, but not female, mating success.Female sea lions consistently had a more diverse diet compared to male sea lions. The authors suggest that this flexibility in food choice is what allowed females to maintain their average body size without foraging further away.However, this flexibility in diet can only take the sea lions so far, and the authors warn that the sea lions' future may not be so rosy.