Effects of physiological changes and social life events on adrenal glucocorticoid activity in female zoo-housed Asian elephants (Elephas maximus)

PLoS One. 2020 Nov 6;15(11):e0241910. doi: 10.1371/journal.pone.0241910. eCollection 2020.

Abstract

Ensuring good health and welfare is an increasingly important consideration for conservation of endangered species and includes breeding of individuals managed under human care. Understanding how factors in the captive environment affect individual animal wellbeing can be aided by long-term monitoring of biological functioning. This study involved longitudinal assessments (4 to 28 years) of reproductive and adrenal hormones in zoo-housed female Asian elephants (Elephas maximus) (age range 4 to ~71 years) to elucidate patterns in adrenal glucocorticoid (GC) activity in association with reproductive and demographic factors, and examine individual response to major social changes. Concentrations of serum and urinary cortisol covaried more consistently with physiological changes (ovarian cycle phase, puberty, pregnancy, lactational anestrus, and age) than with social life events (births, deaths, and facility transfers). Cortisol fluctuated across the ovarian cycle with mean concentrations being higher in the follicular than in the luteal phase, and concentrations were highest in lactational anestrous compared to all other reproductive states. The elephants in this study exhibited substantial individuality in adrenal GC response to major social change, reinforcing the need to assess welfare on an individual basis and to consider factors influencing the impact of perceived stressors, such as social relationships, social support, temperament, and life history. Outcomes from this study deepen our understanding of Asian elephant physiology and highlight the importance of taking intrinsic patterns of hormone secretion into account when evaluating the impact of external factors. Finally, a better understanding of the impact of social change and resiliency in response to real and perceived stressors allows us to improve social management to enhance welfare in both captive settings and free-ranging environments.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adrenal Cortex Hormones / blood
  • Adrenal Cortex Hormones / urine
  • Animal Welfare
  • Animals
  • Animals, Zoo
  • Asia
  • Conservation of Natural Resources
  • Elephants / blood
  • Elephants / physiology*
  • Elephants / urine
  • Endangered Species
  • Estrous Cycle
  • Female
  • Hydrocortisone / blood*
  • Hydrocortisone / urine*
  • Longitudinal Studies
  • Sexual Maturation

Substances

  • Adrenal Cortex Hormones
  • Hydrocortisone

Grants and funding

This work was supported by the Oregon Zoo (https://www.oregonzoo.org), Oregon Zoo Foundation (https://www.oregonzoo.org/about/about-oregon-zoo-foundation), and discretionary funds from the Smithsonian Conservation Biology Institute (https://www.si.edu/unit/conservation-biology-institute). Employers provided financial support in the form of author salaries as follows: Oregon Zoo Foundation (SSG), Oregon Zoo (NW), Smithsonian Conservation Biology Institute (JLB, KLE), North of England Zoological Society, Chester Zoo (KLE). The Oregon Zoo had a role in collection of biological samples; otherwise, funders had no role in the study design, data collection and analysis, decision to publish, or preparation of the manuscript.