As creatures get bigger, they have smaller surface-area-to-body-volume ratios. Fully grown Asian elephants thus pack a lot of mass into a body with a relatively small surface area. And surface area limits how much body heat you can dissipate.
For the study, two female elephants in the Audubon Zoo in New Orleans walked around a half-mile track under various conditions. The outdoor temperature during these sessions ranged from a chilly 8 degrees Celsius to a scorching 35 degrees.
Clear, hot days were the worst. The already limited hide is now itself heated by the sun. With the equivalent of a busted radiator, the elephants retained 56 to 100 percent of their body heat internally. Which could make a mere four hours of exercise fatal. The research on elephant exertion is in the Journal of Experimental Biology. [M.F. Rowe et al., Heat storage in Asian elephants during submaximal exercise: behavioral regulation of thermoregulatory constraints on activity in endothermic gigantotherms]
Fortunately, elephants have ways to beat the heat: shift activity to after dark and, of course, go for a dip.
—Sophie Bushwick
