Desert animals

A xerocole (from Greek xēros /ˈzɪroʊs/, meaning 'dry', and Latin col(ere), meaning 'to inhabit'), commonly referred to as a desert animal, is an animal adapted to live in the desert. The main challenges they must overcome are lack of water and excessive heat. To conserve water, they both avoid evaporation and concentrate excretions (i.e. urine and feces). Some are so adept at conserving water or obtaining it from food that they do not need to drink at all. To escape the desert heat, xerocoles tend to be either nocturnal or crepuscular, most active at dawn and dusk.

Xerocoles have developed a variety of mechanisms to reduce water loss via evaporation. Mammalian xerocoles sweat much less than their non-desert counterparts. For example, the camel can survive ambient temperatures as high as 49 °C (120 °F) without sweating, and the kangaroo rat lacks sweat glands entirely. Both birds and mammals in the desert have oils on the surface of their skin to "waterproof" it and inhibit evaporation.

Desert insects use a similar method, as their cuticles are waxy to prevent water from escaping; however, at critical temperatures (ex. 30 °C (86 °F) for cockroaches), the wax molecules in the cuticle rearrange to become permeable and permit evaporative cooling.

Amphibious xerocoles, such as species of the Phyllomedusa genus of frogs, have wax-like coatings on their skin to reduce water loss. The frogs secrete lipids from glands in their skin: when their skin begins to dry out, they move their limbs over the glands on their backs, and wipe the lipids over their bodies. Other desert amphibians, such as the Cyclorana genus of frogs, avoid desiccation by burrowing underground during dry periods and forming a cocoon from shed skin: rather than being sloughed off, the skin remains attached to create the cocoon. As skin layers amass, water impermeability increases.

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