C - California, Galapagos, and Japanese Sea Lions: Zalophus californianus, Z. wollebaeki, and Z. japonicus

Abstract

This chapter discusses the characteristics, taxonomy, distribution, abundance, and ecology of California, Galapagos, and Japanese sea lions. These are closely related species that together comprise the genus Zalophus. The three sea lions are now regarded as separate species: Zalophus californianus, Z. wollebaeki, and Z. japonicus, respectively. Previously they were typically considered to be geographically isolated subspecies, but recent discoveries of substantial morphological and behavioral differences among them led to their reclassification. California sea lions are highly sexually dimorphic: the weight and length for adult males is about 350 kg and 2.4 m compared to about 100 kg and 1.8 m for adult females. The main breeding areas of California sea lions include the Channel Islands in southern California and Mexican islands off the Pacific coast of Baja and in the Gulf of California. California and Galapagos sea lions breed on sandy beaches and rocky areas on remote islands. Because females must forage at sea during lactation, breeding areas are restricted to regions of high marine productivity. California sea lion rookeries along the Pacific coast are in a very productive upwelling zone, and productivity in the Gulf of California is also very high due to tide- and wind-generated upwelling.