Behavioral characterization of musth in Asian elephants (Elephas maximus): Defining progressive stages of male sexual behavior in in-situ and ex-situ populations

Abstract

Complementary studies of wild and zoo-housed animals offer insight into behavioral variation across a range of conditions including the context under which various behaviors evolved in natural settings. This information can be used to improve the sustainability of in-situ and ex-situ populations and enhance the well-being of individuals. Managed ex-situ populations are critical to the long-term existence of Asian elephants, yet relatively little is known about male reproductive behavior compared to females. Male elephants undergo a unique sexual state called “musth” that further complicates in-situ and ex-situ management strategies. The ability to manage musth males to enhance breeding success and overall wellness of elephants is dependent upon better understanding how intrinsic and extrinsic factors influence male behavioral variation around musth. Here, we observed 62 free-ranging male Asian elephants in Sri Lanka and compared their behavior to observations from 26 elephants managed in facilities around the US. We hypothesized that musth is associated with significant behavioral changes that can be used to define distinct stages in the progression of musth. During observations, we quantified environmental variables and recorded musth status of each focal elephant using visual indicators (temporal gland secretions and urine dribbling). We showed that musth’s behavioral correlates (including changes in locomotion, foraging, alertness, and chemosensory behavior) were remarkably similar in wild and zoo-housed elephants. We also found that behavioral variation around musth was also associated with intrinsic (e.g., musth stage, age) and extrinsic factors (e.g., space availability, temperature) in zoo-housed, but not wild, elephants, indicating that musth is potentially plastic in changing environments. As musth progressed, we noted distinct behavioral signatures that define four stages of sexual activity in male elephants: non-musth, early musth, full musth, and post-musth. Finally, although we did not observe significant changes in overall social behavior (including aggression) during musth, we found that elephants increased the frequency with which they displayed certain behaviors associated with communication (e.g., alertness, chemosensory behavior, ear-flapping) in both populations. Together, these results indicate the significant behavioral changes that occur during musth in wild and zoo-housed elephants, and that musth progresses in distinct behavioral stages that can be easily distinguished by visual indicators. Studies like these serve to provide wildlife managers with information about a species’ unique, evolved behavioral strategies and how these seemingly fixed behaviors may be influenced by intrinsic and extrinsic factors in predictable ways.