Determining sex of Steller and California sea lions utilizing qPCR analysis of scat

Developing methods to identify the sex of pinniped depositors from scat describes demographics of sampled populations and may reveal differential prey consumption between males and females. Sex-specific diet information determines predator impacts on prey populations and informs ecosystem management decisions. Matejusová (et al. 2013) developed qPCR methods to determine the sex of wild harbor seals (Phoca vitulina) from collected scat, which allowed scientists to document sex-specific diet differences across spatial and temporal scales in the Salish Sea (Schwarz et al. 2018). We expand on these methods by developing assays to determine sex from Steller (Eumetopias jubatus) and California (Zalophus californianus) sea lion scats. We acquired scat samples from California and Steller sea lion individuals of known sex housed in the Vancouver and Seattle aquariums. DNA was extracted using a QIAamp Fast DNA Stool Mini Kit and NucleoSpin® DNA Stool extraction kit. Novel Taqman gene expression assays were designed using distinct regions within the zinc-finger X-linked gene (ZFX) and sex-determining region Y gene (SRY) of Steller and California sea lions to be used in qPCR signal amplification. Once finalized, this protocol can be implemented to validate differential prey consumption of male and female Steller and California sea lions in wild populations.