Endocrine Correlates of Musth in Free-Ranging Asian Elephants (Elephas maximus) Determined by Non-Invasive Faecal Steroid Hormone Metabolite Measurements

Ratna Ghosal,André Ganswindt,Raman Sukumar,Polani B Seshagiri,Tobias Deschner

doi:10.1371/journal.pone.0084787

Abstract

The occurrence of musth, a period of elevated levels of androgens and heightened sexual activity, has been well documented for the male Asian elephant (Elephas maximus). However, the relationship between androgen-dependent musth and adrenocortical function in this species is unclear. The current study is the first assessment of testicular and adrenocortical function in free-ranging male Asian elephants by measuring levels of testosterone (androgen) and cortisol (glucocorticoid – a physiological indicator of stress) metabolites in faeces. During musth, males expectedly showed significant elevation in faecal testosterone metabolite levels. Interestingly, glucocorticoid metabolite concentrations remained unchanged between musth and non-musth periods. This observation is contrary to that observed with wild and captive African elephant bulls and captive Asian bull elephants. Our results show that musth may not necessarily represent a stressful condition in free-ranging male Asian elephants.

Highlights

Sexual activity in mature male elephants is predominantly associated with the occurrence of musth [1,2,3], a phenomenon well documented in the Asian elephant (Elephas maximus) since ancient times [4]
Out of the 60 males, 27 were assigned to be in musth based on their physical signs (TGS and/or UD)
Our observations of a population of free-ranging Asian elephants in north-eastern India show that musth bulls have comparatively higher faecal androgen metabolites (FAM) levels than do non-musth males (Figure 1a), a finding consistent with all earlier published data on plasma testosterone levels in captive Asian elephants [1,18,19] as well as on captive and free-ranging African elephants [14,17]

Summary

Introduction

Sexual activity in mature male elephants is predominantly associated with the occurrence of musth [1,2,3], a phenomenon well documented in the Asian elephant (Elephas maximus) since ancient times [4]. In the early 1980s, musth has been recognized in male African elephants Loxodonta africana [3]. Among African elephants, musth periods are usually associated with an increase in aggression, dominance displays and unpredictability, especially towards other bulls in musth [3,8]. Musth may be the most important determinant of dominance among male Asian elephants [9] and this may signal to females a “handicap” [10] through its burden on the animal’s immune system [11]

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Conclusion