Meeting Abstract

98.9  Thursday, Jan. 7  Thermodynamics of Asian Elephant (Elephas maximus) Locomotion: The Functional Significance of Heat Storage and Pinna Vasodilatation ROWE , Michael F*; BAKKEN , George S ; RATLIFF, Joey ; LANGMAN , Vaughan ; Indiana State University, Terre Haute ; Indiana State University, Terre Haute ; Audubon Zoo, New Orleans ; USDA/APHIS mrowe6@indstate.edu

Abstract The large body size of Asian elephants (Elephas maximus) presents a large surface for absorbing solar and thermal energy from the environment (external heat load), while their small surface area to mass ratio makes dissipation of metabolic heat (internal heat loads) challenging. During locomotion metabolic rate in Asian elephants can increase up to 4.5 times resulting in a rise in core body temperature (heat storage). Seasonal variations in environmental conditions may make dissipation of metabolic heat differentially challenging. While the pinna (ears) of elephants have been proposed as thermoregulatory organs no study has examined their significance to heat loss during locomotion. To quantify the thermal energy budget of Asian elephants during locomotion we measured rectal temperature (Tb) and performed thermal imaging before and after exercise in the winter, summer and fall of 2009 on two adult Asian elephants, ranging in mass from 3,447kg to 4,627kg, at the Audubon Zoo in New Orleans, Louisiana. The distance of exercise events were either 945m or 1614m. The change in Tb during these short and moderate distance walks ranged from 0.3 to 1.7 ˚C. Heat storage increased significantly (P<0.05) in the summer. Radiant heat loss from vasodilatation of the pinna also increased significantly (P<0.05) in the summer, however it accounted for only 2% of the total heat loss regardless of season. Due to their small surface area to mass ratio heat loss in exercising elephants occurs at slower rates than metabolic heat production, therefore the majority of heat generated by locomotion is stored.