Thermoregulatory factors in the Karoo dwarf tortoise, Chersobius boulengeri

Abstract

Tortoises are ectothermic and they are dependent on environmental temperature and behaviour for controlling their body temperature within their preferred optimal temperature zone (POTZ). The IUCN-status of Chersobius boulengeri is in January 2018 updated to “Endangered”. More knowledge about this species is necessary for managers to take appropriate conservation measures. To get more insight in the thermoregulatory ecology of Chersobius boulengeri, sex, behaviour, carapace, plastron and cloacal temperatures and environmental temperatures were recorded during a fieldwork period of about six weeks in February and March. The carapace, plastron and cloacal temperatures were not significantly different in C. boulengeri. No difference was found between males and females and active tortoises had a significantly higher temperature than inactive tortoises. Most of the time, the tortoises were hiding in crevices. The body temperature of hiding tortoises relies most on the ceiling, soil and ambient temperatures respectively. The usage of crevices by C. boulengeri results thus in options for controlling their body temperature by radiation, convection and conduction. This species seems to be a thermoconformer by adopting the ambient temperatures in the crevices.