DUMBO鈥橲 big ears didn鈥檛 just get him off the ground 鈥� 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.
鈥淚 wrote to Disney to get some drawings so we could calculate Dumbo鈥檚 dimensions,鈥� says Phillips. By comparing those dimensions with published data on elephants and other animals, the scientists worked out Dumbo鈥檚 likely weight and metabolic rate 鈥� a measure of how much heat he produced. They then estimated how this would increase during flight. 鈥淔light metabolism is roughly 10 times that of resting metabolism,鈥� says Phillips. Finally, they calculated the surface area of Dumbo鈥檚 ears and fed all the numbers into their model.
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They found that if Dumbo鈥檚 ears were any smaller, he鈥檇 suffer severe heat stress while flying. 鈥淲e concluded that he needs big ears not just to fly but to lose the extra heat he produces while flying,鈥� says Phillips. 鈥淏ut in cooler weather, he could actually lose more than he produces.鈥�
John Speakman, who studies the energetics of flight at the University of Aberdeen, says that by studying extreme situations, such as animals that don鈥檛 exist, we can gain fresh insights. For example, why don鈥檛 real elephants have such huge ears? 鈥淭he answer is, with ears that big, they鈥檇 need to compensate for the heat loss by having an enormous metabolic rate,鈥� he says.
Journal reference: Journal of Thermal Biology (vol 26, p 117)
