Cooling down

As well as manufacturing their own body heat, mammals attract a significant amount of ambient heat and as a result, all animals have evolved elaborate cooling systems to counter the damaging effects of over-heating. Be it by the panting of cats or by heat dissipation through the carotid artery retia in an antelope’s head, Mother Nature has provided the means to lower core temperatures. But, some animals attract more heat than others and with the large surface area provided by an Elephant’s skin and its large organs producing more internal heat than other animals, Elephants often need a little extra help.

An Elephant’s external ear, as well as being a very effective sounding board, also acts as a radiator. The backside of each ear is latticed with an extensive network of blood vessels, lying directly under the relatively thin skin of the ear and Elephants flap their ears to waft air over the blood in these vessels. A large bull Elephant has approximately 300 litres of blood in his body and he can circulate this through his ears in 15 minutes. The wafted air cools the skin of the ear, which then absorbs heat from the blood, significantly lowering its temperature before it flows through his brain, thereby lowering his core temperature.

The African Elephant’s ears constitute 20% of its entire surface area, but on very hot days even the flapping of these giant organs is not enough to generate effective cooling and on those days it will use some help: flicking wet river-sand, throwing sticky mud or spraying water onto the backs of its ears significantly reduces the skin’s temperature and hence, the temperature of its blood.

The cool sand or mud sticks to its skin, prolonging the cooling effect better than mere water will do and mud has the added effect of creating an insulating layer of coolness against the skin, as the outer layer dries in the hot sun, ensuring that the heat is drawn off the blood over a longer period. They also use fine-grained dust to speed up the sealing process, ensuring that the mud retains its moisture for longer.

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