Elephants Use 'Hot Spots' to Stay Cool
By Richard Gray, Science Correspondent
With their thick hides and lack of sweat glands, it has long been thought that elephants rely upon their distinctive large ears and bathing in rivers to stay cool in hot climates.
New research, however, has revealed that the world's largest land animals have a secret trick to control their own body temperatures.
Using thermal cameras, biologists have discovered that the creatures' bodies are covered in "hot spots" that can help them lose heat.
By directing their blood supply near to the surface of small patches of skin scattered around their bodies, elephants can lose heat rapidly, allowing them to fine-tune their internal temperature.
Scientists have long been puzzled by temperature regulation in elephants. Typically, animals with large bodies tend to retain more heat because, relative to their bulk, they have a small surface area for heat to escape from.
Elephants, with their heavyweight frames, would appear to be at a disadvantage in the fierce heat of their African and Asian habitats, especially because they lack sweat glands - used for cooling by other mammals - and have tough hides to protect them from spiny bushes and trees.
It was assumed by biologists that the creatures, which weigh up to 13 tons (12 tonnes) when fully-grown, had evolved large ears to help them stay cool. The skin in the ears is thinner, so blood pumped into them cools down more readily.
But findings by researchers at two universities in Vienna have revealed that elephants also able to cool down by increasing the blood flow to skin patches in other parts of their bodies.
Nicole Weissenböck, an ecologist at the city's University of Veterinary Medicine, who led the research, said: "Elephants are the largest terrestrial mammals on earth today.
"They are called pachyderms [from the Greek for "thick skin"] because of their supposed thick and insensitive skin.
"Our study clearly shows that this is only a myth – in fact the elephant's skin must have more regional concentrations of vascular networks that has previously been appreciated.
"It is a fine-tuning mechanism in heat regulation."
The researchers took thermal images of six African elephants at Vienna Zoo as they moved between outdoor and indoor environments to see how the temperature on their skin surface would change.
Bright yellow and white colours indicated the parts of their bodies from which the animals were losing the most heat.
The researchers found up to 15 "hot spots" scattered all over an elephant's body surface, in addition to large patches on the ears.
The study, which is published in the Journal of Thermal Biology, shows how these patches expand as the air temperature increases and more blood flows nearer to the skin surface.
Subsequent experiments showed that elephants in the wild use the same "thermal windows" to control their body temperature.
Elephants have two additional ways to stay cool: ear-flapping, which creates a breeze, and bathing, which cools the creatures when the water evaporates from their skin.
Together with these tricks, the skin hot spots allow the animals to keep their body temperature constant at about 36e_SDgrC – one degree less than humans.
Professor Fritz Vollrath, an expert on elephant behaviour at Oxford University and a trustee of the Save the Elephants charity, said it was possible the hot spots provided localised cooling for specific organs.
He said: "This is an interesting study as it shows that elephants can and do flood blood through their ears independently and can open and close specific areas of their skin for blood cooling."