Abstract
Mammals use endogenously produced heat to maintain a high and relatively constant core body temperature (T(b)). How they regulate their T(b) during reproduction might inform us as to what thermal conditions are necessary for optimal development of offspring. However, few studies have measured T(b) in free-ranging animals for sufficient periods of time to encounter reproductive events. We measured T(b) continuously in six free-ranging adult female African lions (Panthera leo) for approximately 1 year. Lions reduced the 24 h amplitude of T(b) by about 25% during gestation and decreased mean 24 h T(b) by 1.3 ± 0.1°C over the course of the gestation, reducing incidences of hyperthermia (T(b) > 39.5°C). The observation of improved homeothermy during reproduction may support the parental care model (PCM) for the evolution of endothermy, which postulates that endothermy arose in birds and mammals as a consequence of more general selection for parental care. According to the PCM, endothermy arose because it enabled parents to better control incubation temperature, leading to rapid growth and development of offspring and thus to fitness benefits for the parents. Whether the precision of T(b) regulation in pregnant lions, and consequently their reproductive success, will be influenced by changing environmental conditions, particularly hotter and drier periods associated with climate change, remains to be determined.