Steller Sea Lion Research
Assessing the health and fitness in free-ranging populations is logistically challenging and many parameters can be altered by acute stressors, such as capture and handling. Keratinized tissues (tissues that contain the fibrous protein, keratin) are increasingly being used to investigate a suite of parameters to assess diet, contaminants, and steroid hormones. Steroid hormones including cortisol, progesterone, and testosterone have been shown to accumulate in keratinized tissues including hair, baleen and whiskers. Cortisol in hair was related to fatness in polar bears and was correlated to mercury concentrations in males (Bechshøft et al. 2011). In Antarctic fur seals, females sampled from a high density colony had higher hair cortisol concentrations, and across colonies, pup hair grown in utero correlated with maternal hair cortisol concentrations (Meise et al. 2016). These findings demonstrate the utility of measuring hormones in hair of sea lions and fur seals. To date, we have validated the laboratory methods for measuring cortisol, aldosterone, and testosterone in hair of young Steller sea lions (SSLs). Preliminary analysis found all three hormones were detectable in all hair samples with considerable variation between individuals. Currently, archived hair samples with known mercury concentrations are being analyzed to assess in the impact of mercury exposure in young SSLs. The relationship between these steroid hormones and geographic region/ population status, sex, and body condition will also be examined.
- Bechshøft, T. Ø., C. Sonne, R. Dietz, E. Born, M. Novak, E. Henchey, and J. Meyer. 2011. Cortisol levels in hair of East Greenland polar bears. Science of the total environment 409:831-834.
- Meise, K., N. von Engelhardt, J. Forcada, and J. I. Hoffman. 2016. Offspring hormones reflect the maternal prenatal social environment: Potential for foetal programming? PloS one 11:e0145352.