Food and Predation

Photo courtesy of The Busch Entertainment Corporation

California Sea Lions are opportunistic carnivores and feed on more than fifty species of fishes and cephalopods (B.E.C. 2005). Food includes cephalopods, anchovies, herring, Pacific whiting, rockfish, hake, salmon, small sharks, squid and octopuses (Price, 2002). The California sea lion usually does not need to dive very deeply, since most of the food is found in shallow waters, about 26 to 74 meters deep (B.E.C., 2004). However, they can dive to depths of about 274 meters (B.E.C., 2004).

California sea lions tend to feed alone or in small groups unless there is a large quantity of food (Price, 2002). If there is a large quantity of food they may feed in bigger groups (Riedman, 2004). They have been known to feed cooperatively with cetaceans, seabirds and harbor porpoises, and to assemble at the mouths of fresh water rivers where there is steady supply of fish (Price, 2002).

California sea lions that live around islands are considered to have little to no predation, while those living along coast lines have a higher predation rate (Riedman, 2004). The main predators to the Zalophus californianus are the great white shark and the killer whale (Orcinus orca) (Riedman, 2004). Other predators include coyotes, feral dogs, and bald eagles, which prey mostly on the young (OBIS-SEAMAP, 2002). California sea lions live on average 15 to 25 years, and pup mortality may be 10-15% in the first month (B.E.C., 2004).

The alarm reaction of non-breeding California sea lions consists of a frantic dash for the water, which is highly contagious and usually spreads rapidly through an aggregation. The alarm reaction is probably learned by the pups during their first few weeks of life. During their first week or so of life, they do not show any fear of man and do not join in stampedes. Galapagos sea lions show virtually no fear of man, providing evidence that the alarm reaction is learned and "culturally" transmitted in the California population (Peterson, 1967).

These Z.c. wollebaeki pay no attention to their potential human predators in the Galapagos. This suggests that the alarm reaction to humans is learned, as humans have never posed a threat to sea lions on these islands. Photo courtesy of Jessica Long.

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