Water Relations of Crocodiles

Abstract

UNTIL recently, it was thought that reptiles possessed an impervious integument. This is now known not to be the case. Cutaneous water loss has been shown to represent two-thirds or more of the total transpiration from a wide variety of reptile species¹. Experiments at Khartoum on young Nile crocodiles (Crocodilus niloticus L.) have recently shown that in dry air at temperatures from 25° to 40° C, water loss varies from about 5 to 20 per cent of initial body weight in 24 h. The lethal limit of water loss is about 40 per cent of initial body weight. Cutaneous transpiration was estimated by weighing the crocodiles and placing them in plastic bags containing anhydrous calcium chloride, to prevent possible water loss by diffusion, and sealing these around the necks of the animals with adhesive tape. The crocodiles were then placed in desiccators at the required temperatures for 24 h before being reweighed both in and out of the bags. In this way total and respiratory water loss were determined and a measure of the cutaneous loss was obtained by subtraction. At the temperature range mentioned, cutaneous water loss represented an amount varying from about 10 to 75 per cent of the total.