Abstract

The successful rehabilitation and release of stranded cetaceans is the goal of any rescue center. During rehabilitation efforts, however, the activation of a physiological stress response in animals may prevent the realization of this goal. This "alarm reaction" may lead to a number of undesirable and often serious outcomes for animals, such as immune system suppression and contraction band necrosis. To better understand the alarm reaction in the context of rehabilitation efforts, we have been analyzing the serum levels of a number of adrenal "stress" hormones in cetacean species during the events of rehabilitation. In this study we validated the use of commercially available Radioimmunoassay (RIA) kits for cortisol and aldosterone in three species: bottlenose dolphins (Tursiops truncatus), melon-headed whales (Peponocephala electra), and pan-tropical spotted dolphins (Stenella attenuata). Cortisol Coat-A-Count RIA kits were obtained from Diagnostic Products Corporation (Diagnostic Products Corporation, Los Angeles, CA, USA) and aldosterone RIA kits from MP Biomedical (Solon, OH, USA). RIA validations were first performed to establish if these kits were accurately labeling the targeted hormones. Cortisol validations were performed in each species using pooled samples: 5 T. truncatus (1 immature and mature female, 2 immature males, and 1 immature male), 2 P. electra (2 mature females) and 2 S. attenuata (1 mature female, 1 mature male). Mean % binding of ¹²⁵I to serum cortisol was 78.7% for T. truncatus (range = 65.9-89.5), 86.5% for P. electra (range = 74.5-97.0), and 82.2% for S. attenuata (range = 71.7-89.7). Due to limited serum samples, aldosterone validations were limited to T. truncatus and were only performed on pooled samples from 3 animals (2 immature males and 1 mature female). The mean % binding of ¹²⁵I to serum aldosterone for T. truncatus was 79.3% (range = 66.4-88.9). These results indicate the two commercially available RIA kits selected for this work accurately label cortisol and aldosterone in cetaceans. Preliminary analysis of serum cortisol and aldosterone levels in archived samples collected from animals during rehabilitation indicate positive correlations between changes in the levels of these stress hormones and events that occurred during rehabilitation (jumping out of pool, etc.). Other markers such as respiration rate and behavioral changes showed similar results. Monitoring adrenal "stress" hormones may serve as a useful tool for to veterinarians and rehabilitation professionals for the identification of undue stressful events (i.e., extended capture time for exams, loud noises, etc.) during rehabilitation.