Seasonal effects on thermoregulatory abilities of the Wahlberg's epauletted fruit bat (Epomophorus wahlbergi) in KwaZulu-Natal, South Africa

Abstract

Seasonal variations in ambient temperature (Ta) require changes in thermoregulatory responses of endotherms. These responses vary according to several factors including taxon and energy constraints. Despite a plethora of studies on chiropteran variations in thermoregulation, few have examined African species. In this study, we used the Wahlberg's epauletted fruit bat (Epomophorus wahlbergi, body mass≈115g) to determine how the thermoregulatory abilities of an Afrotropical chiropteran respond to seasonal changes in Ta. Mass specific Resting Metabolic Rates (RMRTa) and basal metabolic rate (BMR) were significantly higher in winter than in summer. Furthermore, winter body mass was significantly higher than summer body mass. A broad thermoneutral zone (TNZ) was observed in winter (15–35°C) compared with summer (25–30°C). This species exhibited heterothermy (rectal and core body temperature) during the photophase (bats' rest-phase) particularly at lower Tas and had a low tolerance of high Tas. Overall, there was a significant seasonal variation in the thermoregulatory abilities of E. wahlbergi. The relative paucity of data relating to the seasonal thermoregulatory abilities of Afrotropical bats suggest further work is needed for comparison and possible effects of climate change, particularly extreme hot days.