Joshua Tree National Park - Reptiles

Reptiles are better adapted to life in arid lands than are most birds and mammals. Being ectotherms (obtaining their body heat solely from the external environment), reptiles have a much lower cost of living than do birds and mammals which produce their own body heat using a great deal of food in the metabolic process. In desert lands, where primary productivity (plant growth) is low, reptiles are thus able to maintain larger populations on the limited food supplies than is possible for birds and mammals. The most limiting factor for life on the desert is drinking water. Reptiles are pre-adapted to such arid conditions. They do not need water for cooling because they do not perspire or pant. They just crawl into a cool hole in the heat of the day.

Their scales also greatly retard water loss through the skin. In addition, reptiles do not need water for excretion; they produce no urine. Their nitrogenous wastes are excreted as a solid: uric acid. Reptiles can get all the water they need from the food they eat. Although desert tortoises and probably most other reptiles will drink water when it appears after summer rains, many lizards and snakes probably go their whole lives without a drink of water. The reptiles of Joshua Tree National Park include one tortoise, 18 lizards, and 25 varieties of snakes