Meeting Abstract
36.6 Friday, Jan. 4 Adaptations of Elephant Skin for Non-Evaporative and Evaporative Heat Loss DUNKIN, R.C.*; WILLIAMS, T.M.; KOOPMAN, H.N.; U.C. Santa Cruz; U.C. Santa Cruz; U.N.C. Wilmington dunkin@biology.ucsc.edu
Despite lacking sweat glands, elephants have among the highest rates of cutaneous water loss (CWL) of a variety of arid dwelling herbivores. Though the unique morphology of elephant skin has been recognized, neither its thermal nor water barrier properties have been investigated. We measured thermal conductivity (W m-1oC-1) and conductance (W m-2oC-1) as well as cutaneous water loss (CWL, mg cm-2 hr-1) and resistance (s cm-1) of integument from Asian (n = 4) and African (n = 2) elephants and correlated these values with morphological and compositional analysis of the skin. Manatee (n=5) and pig (n=5) integument were also included for comparison. We found significant inter and intra-species variation in morphology and composition of the integument which corresponded to differences in both the thermal and water barrier properties. The thermal conductivity of Asian (0.19 ± 0.01 W m-1oC-1) and African elephant (0.23 ± 0.13 W m-1oC-1) integument approached the upper limit of previously measured values as a result of high water and low lipid content. CWL was significantly greater (p<0.0001, F = 54.21) and resistance significantly lower (p<0.0001, F = 35.11) in both the elephant and manatee integument relative to that of the pig at all measured temperatures. All four species demonstrated a significant increase in resistance at the highest temperature treatment (39.7oC) but this was most pronounced in elephants and manatees and may correlate with the transition temperature of stratum corneum lipids. Our results indicate that elephant integument conducts heat up to 11 times better than mammals with arctic or sub-arctic pelage and loses water at rates that are comparable to some amphibians, allowing elephants to maximize both non-evaporative and evaporative heat loss.
