Potential physiological costs of leadership in African elephants: elevated faecal glucocorticoid metabolites in a matriarch

Abstract

In African elephant (Loxodonta africana) societies, matriarchs hold the highest social rank, relying on long-term ecological knowledge to maintain group cohesion and coordinate collective movement. Although such leadership is widely recognized as behaviourally and cognitively demanding, we seldom quantify potential physiological costs. Here, we report higher faecal glucocorticoid metabolite (fGCM) concentrations in a matriarch compared to all other members of her family group in a semi-arid, fenced reserve in the Nama-Karoo biome of South Africa. From 2022–2024, we collected 372 faecal samples from all 18 individuals in the population and analyzed fGCM concentrations using a Bayesian framework. Demographic variables did not predict fGCM levels, but individual-level variation was noted. Posterior estimates indicated that the matriarch, Zinkwazi, exhibited higher fGCM concentrations than any other herd member. As no pregnancies occurred during the study period, elevated fGCM levels are unlikely to reflect reproductive state, suggesting instead that responsibilities of leadership may contribute to sustained glucocorticoid output. These findings highlight the possibility that matriarchal leadership carries measurable physiological costs. Understanding such costs may provide new insight into elephant social dynamics, welfare, and management in constrained or resource-limited landscapes.