Thermoregulation of Savanna Chimpanzees: Quantifying Heat Balance in a Marginal Habitat Using NicheMapR

Abstract

Temperature constrains the distribution, behavior, and physiological performance of animals. As climate change intensifies, the ability of wildlife to maintain thermal balance will play a critical role in determining population persistence. Among African great apes, the West African chimpanzee (Pan troglodytes verus) inhabits a particularly broad range of habitats, but the population at Fongoli, Senegal, lives in one of the most climatically extreme regions of any chimpanzee population. This study investigates whether savanna chimpanzees face elevated physiological costs compared to those in more thermally buffered, forested habitats, and how these costs may shift under future warming. Using a mechanistic biophysical modeling approach (NicheMapR), we simulate heat and mass exchange between chimpanzees and their environments to estimate two key metrics of thermal stress: metabolic rate and evaporative water loss. We compare these values across one savanna national park, Niokolo Koba, and three forested national parks, Taï, Kibale, and Loango, under both historical and projected mid-century climatic conditions. Our findings show that savanna habitats impose consistently higher thermoregulatory costs and that future climate scenarios exacerbate these physiological burdens, particularly in marginal habitats. These results offer a novel, quantitative framework for evaluating primate vulnerability under global change and contribute to broader efforts to understand the physiological limits of species survival in warming ecosystems.