August 24th, 2012
How Desert Animals Beat The Heat
Deserts! Lizards, rattlesnakes, and cacti come to mind. Can anything else survive? Yes! Many animals have either learned how to cope or come equipped with ingeniously designed systems to “beat the heart.”
Many animals cope by avoiding the heat as much as possible. They limit activity to the cooler morning or evening hours, and spend much of the day in a cool, moist burrow or in the shade of rocks or vegetation. Others minimize heat absorption by aligning themselves parallel to the sun’s rays, or seeking the shade of a telephone pole! When the going gets really tough, larger animals may migrate to cooler areas while some smaller ones go into estivation, a condition similar to hibernation.
Desert animals exhibit various temperature regulation methods. Many have light coloration which reflects much sunlight or heavy fur which insulates against intense heat. In some, the basal metabolic rate can decrease to minimize heat production during the hottest part of the day. In others, the blood flow to the skin increases to dissipate body heat (The large, heavily-vascularized ears of the jackrabbit act like radiators!). Some animals expose thinly-haired belly regions to the “cooler” air to dissipate body heat, while many take advantage of evaporative cooling by panting or wetting their fur in puddles or streams or by drooling.
There are also many ingenious solutions to cope with the water shortage. Certain small animals have extremely efficient water conservation mechanisms. For example, the kangaroo rat is able to live its entire life on dry seeds, without ever taking a drink! Its many complex specializations help conserve the tiny bit of water produced in the breakdown of its food – its efficient kidneys and intestines excrete extremely concentrated wastes and the convoluted passages in its nostrils prevent water loss from the lungs. Some larger animals are able to tolerate extensive dehydration. Camels and donkeys, for instance, can tolerate water loss up to 25% of their body weight. (By comparison, humans can stand only 12%.) Amazingly, donkeys can rehydrate from a 25% water loss in less than 2 minutes!
Are these amazing specializations the result of time, chance, and natural processes? Not likely! Complex, highly coordinated systems and specialized behavior as seen in desert animals reflect the handiwork of an Intelligent Designer.
By Dave Nutting
Originally published in the May/June 1991 Think and Believe newsletter.
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