Big ears

 作者:巢哳     |      日期:2019-03-07 04:04:00
By Ian Sample Dumbo’s big ears didn’t just get him off the ground – they stopped him overheating, say researchers. Their study of heat loss from the elephant also shows that his cooling system was so efficient he would have died of hypothermia if he rested for too long. Elephants are known to cool themselves by pumping blood through their ears. To find out how effective the strategy is, Polly Phillips and James Heath of the University of Illinois in Urbana-Champaign created a computer model to show how much heat was lost from ears of different sizes in various ambient conditions. Then a colleague enquired how Dumbo might fare. “I wrote to Disney to get some drawings so we could calculate Dumbo’s dimensions,” says Phillips. By comparing those dimensions with published data on elephants and other animals, the scientists worked out Dumbo’s likely weight and metabolic rate – a measure of how much heat he produced. They then estimated how this would increase during flight. “Flight metabolism is roughly 10 times that of resting metabolism,” says Phillips. Finally, they calculated the surface area of Dumbo’s ears and fed all the numbers into their model. They found that if Dumbo’s ears were any smaller, he’d suffer severe heat stress while flying. “We concluded that he needs big ears not just to fly but to lose the extra heat he produces while flying,” says Phillips. “But in cooler weather, he could actually lose more than he produces.” John Speakman, who studies the energetics of flight at the University of Aberdeen, says that by studying extreme situations, such as animals that don’t exist, we can gain fresh insights. For example, why don’t real elephants have such huge ears? “The answer is, with ears that big, they’d need to compensate for the heat loss by having an enormous metabolic rate,” he says. More at: Journal of Thermal Biology (vol 26,