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| Reptiles
are closely associated with the desert in many peoples minds. This seems
to be based partly on reality and partly on perception. Reptiles do form
a very conspicuous part of the vertebrate fauna of warm deserts such as
are found in Joshua Tree National Park. There may not be any larger number
of reptiles in the desert than in neighboring less arid areas, but the lack
of dense vegetation on the desert certainly makes them easier to see. Many
of the lizards are especially conspicuous as they bask atop boulders or
other elevated sites. |
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| 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 |
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last modified: 05/24/02
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