Fauna: Like the plants, the animals of the desert have evolved an array of strategies for dealing with aridity.
Reptiles with their waterproof skin, production of uric acid instead of urine, hard-shelled eggs, and ability to gain body heat directly from the sun and to retreat to shade or underground to avoid heat are exceptionally well adapted to drylands and, not surprisingly, diverse there.
Many birds in the North American deserts, so fragmented by mountains offering humid habitats and permanent streams, simply fly to free water and so are not limited by the lack of open water. They maintain breeding seasons like other temperate zone birds synchronized by changing photoperiods.
In Australia, where the desert geography is quite different and aridity more pervasive, bird populations synchronize their breeding readiness according to cues of rainfall, however erratic and sporadic that may be.
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