July 11, 2013
Water Helps Elephants Keep Their Cool On Hot Summer Days
Lee Rannals for redOrbit.com - Your Universe Online
Researchers writing in The Journal of Experimental Biology say that elephants depend on water to keep cool during the hot months.Elephants are known to keep cool in a number of ways, including using their enormous ears as fans or radiators. They also depend on their hair to keep from being overheated. However, the species rarely stray away from water, so scientists decided to look into the role evaporative cooling plays in keeping elephants cool at different temperatures.
The team started off by measuring how much water elephants lost by evaporation from their skin over a range of temperatures. In order to do this, they used 13 trained African and Asian elephants from three nearby zoos. The scientists measured water loss from evaporation by passing a stream of air over their skin and measuring the water content of the air before and after.
Robin Dunkin, a researcher from University of California, and colleagues found that as temperatures rose, the amount of water lost by evaporation from the skin increased exponentially. However, Dunkin said that hot air can carry more water and that can drive more evaporation.
Researchers found that overall cutaneous water evaporation was still high at higher temperatures. After treating the elephants to an invigorating and cooling shower, the team saw evaporation rates increased further.
Scientists determined that during the summer months the elephants increased their skin's permeability. Altogether, the findings suggest that elephants are more concerned with using water to cool themselves down than conserving it.
Dunkin and colleagues plan to use the data to model how important evaporative cooling is for an elephant's thermal budget. Even at low temperatures, evaporative cooling played a role, but by the time temperatures hit their highest, it was the only option left for elephants wanting to cool down.
The study suggests that water dependency is too simple of an idea, and it is really more climate dependent than that. Dunkin said that an elephant in subtropical South Africa would need to dedicate about 23 quarts per day of water towards cooling, whereas an elephant in the semi-arid Namibian savannah would need nearly five times that amount.
Elephants' time in the water could be attributed to the species' roots. In 2008, researchers found that ancient elephants used to live partially in the water. Scientists from several universities determined that Moeritherium, an ancient elephant relative that lived more than 37 million years ago, spent most of its time in rivers and swamps.