Diurnal rhythm, temperature and water relations of the African toad, bufo regularis

B. regularis Reuss is nocturnally active, having an endogenous rhythm that is not accelerated in darkness or retarded by constant light. The rate of water-loss is correlated with the saturation deficiency of the air and there is no control of transpiration. Pulmonary ventilation, however, plays a significant part in evaporative cooling. The lethal temperature for one hour's exposure in moist air is 39°C: in dry air a body temperature of 42°C has been recorded from a living toad. There is no correlation between rate of water-loss and the point at which dehydration becomes lethal. The maximum water-loss survived is 50% of normal body weight. The rate of water-uptake is not influenced by ambient air temperature-it is greatest in toads desiccated below 10 to 15% of original weight and declines as rehydration proceeds.