Monitoring stress hormones in rehabilitated and captive otariids

Abstract

Cortisol and corticosterone are the primary mammalian stress hormones released in response to a perceived stressor. Cortisol is rapidly metabolized in the blood, while corticosterone is the dominant product in fecal material. Radioimmunoassay procedures to measure fecal corticosterone and serum cortisol in California sea lions were validated, and adrenal response to surgical and non-surgical procedures was assessed. Other objectives included seasonal and behavioral variability in fecal corticosterone concentrations in captive Steller sea lions, as well as adrenal response to various stressors of a rehabilitated Steller sea lion. There was a significant (P ... 0.05) adrenal response for rehabilitated California sea lions that underwent minor invasive surgical procedures. The small sample size in this study allowed the identification of a correlation of season and behavior in three captive Steller sea lions. This study found that peak fecal corticosterone values reflected responses to acute stressors during rehabilitation for a Steller sea lion pup. Overall, fecal corticosterone was an adequate tool for monitoring stress non-invasive1y in California and Steller sea lions. In turn, the results indicate that California sea lions may be a suitable surrogate species to study the adrenal response to more invasive procedures that may be used in Steller sea lions.