Large animals that inhabit the desert have evolved a number of adaptations for reducing theeffects of extreme heat. One adaptation is to be light in color, and to reflect rather than absorbthe Sun's rays. Desert mammals also depart from the normal practice of mammalian maintainiNG aconstant body temperature. Instead of trying to keep down the body temperature deep insidethe body, which would involve the expenditure of energy, water and desert mammals allow theirtemperatures to rise to what would normally be fever height, and temperatures as high as 46degrees Celsius have been measured in grant's gazelles. The overheated body then cools thedown during the cold desert night, and indeed the temperature may fall unusually low by dawn,as low as 34 degrees Celsius in the camel. This is an advantage since the heat of the first fewhours of daylight is absorbed in warming up the body, and an excessive buildup of heat doesnot begin until well into the day.Another strategy of large desert animals is to tolerate the loss of body water to a point thatwould be fatal for non-adapted animals. The camel can lose up to 30 percent of its body weightas water without harm to itself, whereas human beings die after losing only 12 to 13 percent oftheir body weight. An equally important adaptation is the ability to replenish this water loss atone drink. Desert animals can drink prodigious volumes in a short time, and camels have beenknown to imbibe the over 100 liters in a few minutes. A very dehydrated person, on the other hand,cannot drink enough water to rehydrate my at one session, because the human stomach is notsufficiently big and because a too rapid dilution of the body fluids causes death from waterintoxication. The tolerance of water loss is of obvious advantage in the desert, as animals do
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