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. 2025 Jun 24;15(13):1863.
doi: 10.3390/ani15131863.

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

Kaitlyn M Campbell  1   2 , Chelsi J Marolf  1   3 , Peter E Buss  4 , Kari A Morfeld  1   5
Affiliations

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

Kaitlyn M Campbell et al. Animals (Basel). .

Abstract

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.

Keywords: cortisol; elephant; glucose; insulin; leptin; progesterone; prolactin; testosterone.

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Conflict of interest statement

Authors Kari A. Morfeld, Kaitlyn M. Campbell, and Chelsi J. Marolf were employed by the company For Elephants. Author Kari A. Morfeld was employed by the company Morfeld Research & Conservation. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Figures

Figure 1
Figure 1
Hormone concentration by age class in female African elephants for serum (a) progesterone, (b) prolactin, (c) G/I ratio, and (d) leptin. The bold horizontal line represents the median, the shaded area represents the 25th and 75th interquartile range, and whiskers extend to the minimum and maximum values. Asterisks represent a significant difference between adult females and other age groups. Outliers were excluded from statistical analyses but have been retained in figures for transparency.
Figure 2
Figure 2
Serum testosterone concentration by age class in male African elephants. The bold horizontal line represents the median, the shaded area represents the 25th and 75th interquartile range, and whiskers extend to the minimum and maximum values. Asterisks represent a significant difference between adult females and other age groups. Outliers were excluded from statistical analyses but have been retained in figures for transparency.
Figure 3
Figure 3
Serum testosterone concentration varied with the season in male African elephants. The bold horizontal line represents the median, the shaded area represents the 25th and 75th interquartile range, and whiskers extend to the minimum and maximum value. Outliers were excluded from statistical analyses but have been retained in figures for transparency.
Figure 4
Figure 4
Serum progesterone metabolite concentration as it varies by cortisol and season. Trendlines show predicted values based on a GLM, including season and cortisol as predictors. Shaded areas represent 95% confidence intervals.
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