Introductory Remarks and the Natural History of the California Sea Lion

Abstract

The following section is an in-depth analysis of the effect of the El Niño on one species, the California sea lion (Zalophus californianus). The organization of this section differs from the others in that the papers are based upon topics rather than by studies of one or two species at a particular location. The large number and diversity of studies on the California sea lion which were being conducted simultaneously during the El Niño year enables us to view the phenomenon from many different angles. In order to accomplish this the authors involved have combined data sets from several studies, sites, or islands wherever possible. Since the effects of El Niño were more subtle at higher latitudes, concurrence between several studies strengthens the conclusion that observed effects were indeed due to the El Niño. The papers may be considered, then, as pieces of a larger puzzle which collectively allow us to deduce the mechanisms which shape the immediate behavior, as well as evolution, of this species. The topics range from studies of population dynamics (Chaps. 11, 12, 13, 17) to female attendance (Chap 14), foraging behavior (Chap 15), energetics (Chap. 16), and diet (Chap. 17). Pup development with respect to growth (Chaps. 17, 18), milk intake (Chap. 19), and behavior (Chap 20), as well as yearling behavior (Chap. 21) are also considered. Figure 1 is a map of the study sites included in this section.