Zoo Tales: Animals Beat Heat in Varying Ways
On these summer days when temperatures reach into the 90s -- and sometimes even three-digit temperatures -- humans can learn a little about keeping cool from animals.
Although snakes, amphibians and other "cold-blooded" creatures have no inner thermostat and are only as hot or cold as their surroundings, "warm-blooded" animals have ways of raising or lowering their body temperatures.
At the North Carolina Zoo and at many other zoos and animal facilities, keepers help the animals through a variety of cooling techniques from putting ice into the exhibits for the animals to wallow in to air-conditioned holding areas to ponds within the exhibits.
Other means involve giving the animals cool treats such as frozen buckets of water containing the animal's favorite food or misters in their off-exhibit holding areas.
On particularly hot days, the doors to the animals' holding areas (often air-conditioned) are left open so that the animals have the option to go back inside the cooler areas if temperatures get unpleasantly high for them.
But in the wild, and even with domesticated animals, there are many fewer options, and most cooling is done through nature's own individual techniques.
Most cooling of the body -- in humans and other animals -- involves blood flow. For humans, blood is crucial to cooling. When we become overly hot, our skin turns red because blood is moving to the skin's surface to radiate away body heat. About 75 percent of our cooling results from this radiation. (Sweating and evaporation account for another 15 percent, and about 10 percent escapes through our breathing.)
Like humans, most canines radiate away about 75 percent of their heat. But unlike humans, they hardly sweat at all and release the rest of their body heat by panting. (This is why, on hot days, dogs shouldn't be left inside cars for long periods.)
Although cats, domesticated and wild, have more sweat glands than dogs, they use the evaporation of their licking to help cool themselves.
It's a little different in some of the zoo's animals. Elephants, for example, use their ears not just for hearing but as one of their means of cooling down. Although they use these great flaps to fan themselves, this cooling technique is much more sophisticated. Their ears are filled with blood vessels and have little insulating fat. As blood passes through an elephant's ears, it's cooled by the air -- aided by the fanning.
Also, like many animals at the N.C. Zoo, the elephants have their own pond in which to cool off, sometimes submerging themselves almost completely.
Generally, among warm-blooded animals, long ears, necks, limbs and tails are not only used for locomotion, protection and feeding, but also as a means of getting rid of excess body heat. A mouse's tail, for example, acts like a giant heat radiator. Not surprisingly, the fennec fox of the arid Sahara region has much larger ears than its cousin the Arctic fox, which has small, pike-like ears.
Again generally speaking, the more body surface an animal has -- relative to its weight -- the better it can tolerate heat. The grizzly bear, with its relatively short limbs and great bulk, is suited for cold climates; whereas, animals such as camel, that have to deal with extremely high temperatures, have developed long, lanky legs, necks and tails. Camels also produce water as they digest dry food, so water intake can be slight. They've also developed the ability to suck out every bit of moisture from their waste products before those leave the body.
In addition, because of the camel's unusual red-blood cell formation, it can become 35 to 40 percent dehydrated and still have adequate blood circulation. In humans, death is almost a given when dehydration reaches 12 percent.
To see first-hand how keepers help the animals stay cool and beat the heat at the N.C. Zoo, visit the park Aug. 8 or 9 for the annual ZooCOOL event.
Tom Gillespie works for the public affairs office at the N.C. Zoo.
More like this story