Meeting Abstract

116.6  Saturday, Jan. 7  Radiant heat loss in the pinnae of exercising elephants: pinna recruitment or regional non-pachyderm? ROWE, M. F.*; BAKKEN , G.S.; RATLIFF , J.; HAGAN , D.; THEISON, W.; Indiana State University; Indiana State University ; Audubon Nature Institute; Indianapolis Zoo; Pittsburgh Zoo

Abstract African (Loxodonta africana) and Asian elephants (Elephas maximus) are characterized by thick skin, gigantic body size and large pinnae. Pinnae are believed to play a significant role in thermoregulation. During locomotion the pinnae are held tightly against the body. Radiant heat transfer occurs in the anterior pinna surfaces. The anterior pinna surfaces accounts for about 7.4% and 2.6% of the total surface area in African and Asian elephants, respectively. The percentage of metabolic heat is often used to reference the amount of heat loss in the pinnae. Heat production in elephants increases 2 to 5 fold as a result of slow to moderate walks. If pinnae are independently recruited, the proportion of radiant heat loss from the pinna relative to total radiant heat loss will increase as a result of exercise. We sought to determine whether post-exercise increases in radiant heat transfer in pinnae of elephants occurred independently of the increases in total radiant heat loss. We performed pre- and post-exercise thermal imaging of the pinnae, and whole bodies of African (n=7) and Asian elephants (n=2). Exercise trials (n= 58 trials, totaling 96 km) were conducted during three seasons, over ambient air temperatures ranging from 5 to 34.5°C.There was no statistically significant difference (P≥0.05) between the pre- and post-exercise proportion of total radiant heat loss accounted for by radiant heat loss from the pinnae. Regardless of environmental conditions, radiant heat loss from the pinnae accounts for 7.4% of the pre-exercise and 7.8% of the post exercise radiant heat loss in African elephants and 2.5% of pre- and post-exercise total radiant heat loss in Asian elephants.