# Bridging the Gap: Using Wild African Elephant Metabolic, Reproductive, and Stress Hormone Profiles to Enhance Management in Human Care

## TL;DR

This study provides hormone profiles of wild African elephants to help zoos improve the health and reproduction of elephants in human care.

## Contribution

The study establishes baseline hormone values for wild African elephants, linking metabolic, reproductive, and stress hormones for the first time.

## Key findings

- In females, progestogen and prolactin levels were highest in adults and not correlated with glucose-to-insulin ratio or leptin.
- In males, testosterone levels were higher in adults and predicted by the glucose-to-insulin ratio.
- Seasonal variations showed higher testosterone and lower cortisol in males during the rainy season.

## Abstract

We aimed to establish baseline data for key metabolic, reproductive, and stress hormones in wild elephants, providing a critical reference for zoos to assess and refine their management strategies. Zoos have long faced challenges in managing the reproductive health and body condition of African elephants, with increasing concerns about the connection between obesity and infertility. Understanding these natural hormone patterns in wild elephants can help zoos adjust diets, exercise, and social management to better mimic natural conditions. This may improve overall health, body condition, and reproductive success for zoo-managed African elephants.

Understanding hormone patterns in free-ranging African elephants can provide critical insights for the management of elephants in human care, particularly in addressing reproductive anomalies and the rising prevalence of obesity in zoo populations. This study is the first to establish baseline values for glucose, insulin, and leptin, and their potential relationships with reproductive and stress hormones. We measured the hormones in serum samples collected opportunistically in Kruger National Park between 2000 and 2016. Endocrine profiles were compared across age groups in both male and female elephants and between the wet and dry seasons. In females, progestogen and prolactin levels were highest in adults, and were not significantly correlated with the glucose-to-insulin (G/I) ratio or leptin. In males, testosterone levels were higher in adults, and the G/I ratio was a significant predictor of testosterone concentrations. Seasonal variations revealed that, in males, testosterone levels were higher, and cortisol concentrations were lower during the rainy season. In females, cortisol concentrations were negatively associated with progestogen levels during the dry season. These benchmarks offer zoos a reference point to assess whether current management approaches are effective, and how natural variation with the season may impact hormone levels.