| dc.description.abstract | The annual musth cycle of adult Asian elephant bulls is characterized by behavioral, physical and physiological changes. Male elephants in musth show heightened aggression, increased restlessness, reduced feeding activity and increased searching for oestrous females. During musth, oily temporal gland secretions, continuous urine dribbling and a loss of body condition are commonly seen. Musth is assumed to correspond with elevated levels of circulating androgens. In addition, an elevation in circulating glucocorticoid concentrations has been reported, presumably because musth is a stressful event. Although previous studies have examined both androgen and glucocorticoid profiles in adult male elephants, there is little information about the profiles of these hormones during the complete musth cycle. The objective of this study was to compare cortisol concentrations in serum and feces and to determine whether there is any relationship between the two and thereby to determine whether non-invasive measurements give a reliable indication of physiological stress status. The second objective was to investigate changes in the cortisol profiles of elephant bulls during the non-musth, pre-musth, musth and post-musth periods over the course of a calendar year and to examine the relationship with testosterone profiles.
Serum and fecal samples were collected every 2 weeks during a 17 month period from ten captive adult Asian bull elephants. Testosterone and cortisol concentrations were measured using a validated enzyme immunoassay (EIA). Cortisol concentrations varied greatly during the study period, but there was no clear correlation between serum cortisol and fecal cortisol concentrations. Testosterone concentrations also showed great variation during the course of the musth cycle, and a positive correlation between fecal cortisol and fecal testosterone concentrations was apparent. With regard to the various stages of the musth cycle, a significant difference was found only between serum cortisol and the stages of the musth cycle. No significant differences in testosterone concentrations were apparent during the different stages of the musth cycle. The lack of clear changes in fecal testosterone concentrations during the musth cycle was unexpected and contradicts previous small scale studies; clearly, more research is needed to determine the hormonal changes underlying the musth cycle in Asian elephant bulls. | |
