Potential California Sea Lion (Zalophus californianus) Parturitions After the Pupping Season

We present data that suggest some California sea lion (Zalophus californianus) females gave birth after the pupping season (June-July) in colonies on the west coast of the Baja California Peninsula and in the Gulf of California, Mexico. In June and July of 2010, we captured and tagged pups to estimate their growth rates during their first year of life on Santa Margarita Island (Figure 1). We returned to the colony in November 2010 and February 2011 to capture and weigh the tagged pups, as well as addi-tional untagged pups. Surprisingly, among the newly captured pups, we found pups of similar weight and size to pups captured in July 2010 (pupping season). When we applied the estimated growth rates for U.S. colonies in retrospect, we determined that the pups captured in November 2010 must have been born between August and September of the same year, while the pups captured in February 2011 must have been born between October and November 2010. Another opportunistic observation was obtained in November 2019, when we sighted an apparently pregnant adult female at the Los Islotes colony. This is the first report on births after the pupping season in any pinniped.