Measuring Saliva Progesterone in the California Sea Lion Zalophus californianus

Two captive mature female California sea lions (Zalophus californianus) were trained to provide saliva samples for the purpose of diagnosing of pregnancy at an early stage and monitoring reproductive cycles. Saliva was collected from 1 to 4 times per week from autumn of 1996 to spring of 2000, and the progesterone concentration in the saliva was measured by enzyme immunoassay (EIA). In spite of differences between the two sea lions used in the study, the data thus obtained allowed us to plot their annual reproductive cycles and to diagnose pregnancy a few months earlier than possible using an ultrasonoscope. A comparison of progesterone concentrations in plasma and in saliva failed to show correlation in one of the two animals included in this study, however it was suggested that refining the sampling method will improve this correlation.