Hormonal variation and temporal dynamics of musth in Asian elephants (Elephas maximus) are associated with age, body condition and the social environment

Chase A LaDue; Kathleen E Hunt; Wendy K Kiso; Elizabeth W Freeman

doi:10.1093/conphys/coad019

Hormonal variation and temporal dynamics of musth in Asian elephants (Elephas maximus) are associated with age, body condition and the social environment

Conserv Physiol. 2023 Apr 25;11(1):coad019. doi: 10.1093/conphys/coad019. eCollection 2023.

Authors

Chase A LaDue^{1

2}, Kathleen E Hunt^{3

4}, Wendy K Kiso^{5

6}, Elizabeth W Freeman⁷

Affiliations

¹ Department of Environmental Science and Policy, 4400 University Drive, MSN 5F2, George Mason University, Fairfax, VA 22030, USA.
² Oklahoma City Zoo and Botanical Garden, 2000 Remington Place, Oklahoma City, OK 73111, USA.
³ Department of Biology, George Mason University, 10900 University Boulevard, Manassas, VA 20110, USA.
⁴ Smithsonian-Mason School of Conservation, 1500 Remount Road, Front Royal, VA 22630, USA.
⁵ White Oak Conservation Foundation, 581705 White Oak Road, Yulee, FL 32097, USA.
⁶ Colossal Biosciences, 3309 Elm Street, Dallas, TX 75226, USA.
⁷ School of Integrative Studies, 4400 University Drive, MSN 5D3, George Mason University, Fairfax, VA 22030, USA.

Abstract

The sustainability of endangered Asian elephants in human care is threatened in part by low breeding success and concerns over individual animal wellbeing. Male elephants have received less research attention compared to females, yet males deserve special consideration due to their unique reproductive biology (particularly the sexual state of "musth") and the complex interaction of physiological, environmental, and social pressures they face. We measured fecal androgen metabolites (FAMs), fecal glucocorticoid metabolites (FGMs), and fecal triiodothyronine metabolites (FT3s) collected weekly over approximately 12 months from 26 male Asian elephants housed in zoos across the US, hypothesizing that FAM, FGM, and FT3 concentrations would be associated with temporal correlates of musth and would vary further with intrinsic (musth status, age, body condition) and extrinsic (social environment) factors. The duration of each musth episode was positively associated with exposure to male conspecifics and negatively associated with body condition. Further, elevated FAM concentrations were associated with social exposure, age, and body condition, and FGM concentrations also varied with age and body condition. FT3 concentrations were not associated with any factor we measured. We also identified periods of lower FAM concentration than confirmed musth episodes (but still higher than baseline FAM concentrations) that we termed "elevated FAM episodes." The durations of these episodes were negatively correlated with exposure to other male elephants. Together, these results provide evidence that hormone profiles (including those that are predicted to change around musth) vary significantly between male Asian elephants in a way that may be attributed to intrinsic and extrinsic factors. Studies like these serve to enhance the sustainability of ex-situ populations by providing wildlife managers with information to enhance the health, welfare, and reproduction of threatened species like Asian elephants.

Keywords: androgens; glucocorticoids; health; musth; sustainability; thyroid hormones; welfare.