Meeting Abstract
6.11 Jan. 4 Seasonal Changes in Evaporative Water Loss in African Elephants L. africana DUNKIN, R.C.*; WILLIAMS, T.M.; WILSON, D.; MATTHEWS, C.; Univ. of California, Santa Cruz; Univ. of California, Santa Cruz; Wildlife Safari; Wildlife Safari dunkin@biology.ucsc.edu
Elephants occupy habitats with seasonally sustained high temperatures and low water availability. Despite this, both the ecology and thermoregulatory physiology of elephants suggest that these large mammals are highly water dependent. Although they lack sweat glands, evaporative water loss (EWL) is considered important for heat dissipation in elephants but has not been systematically measured across body sites or seasons. To evaluate variability in EWL in this mammal, we measured skin surface temperature, heat flux, and EWL for three African elephants at Wildlife Safari in Winston, OR. Comparisons were made across seasons for 5 body sites before and after bathing. Our results indicate that surface temperatures of the belly, foot, and inner ear were similar and were higher than the temperatures at the shoulder for both dry (p<0.0001; F = 45.18) and wet (p<0.0001; F = 18.47) skin. Outer ear temperatures were as much as 15oC lower than those for all other body sites. Heat flux varied with body site, with thermal windows (e.g. inner and outer ear) showing significantly lower heat flux in winter than in summer (p = 0.01; F = 7.5). Heat flux from wet skin was generally higher than from dry skin, but this trend was not significant. Evaporative water loss from dry skin was 50% higher in summer compared to winter [mean � SE (mg min-1), summer = 7.09 � 0.33 and winter = 4.74 � .33] (p = 0.02; F = 5.84). When the skin was wet, there was no significant difference in EWL between seasons. If surface area is accounted for, EWL appears to significantly contribute to the high water demand of African elephants particularly during warm seasons. For an elephant with a surface area 20.7m2, the water lost to evaporation in summer and winter is 107L day-1 and 72L day-1, respectively. These values represent 47% and 32% of the average daily water consumption (225L day-1) for this species. Such high levels of water consumption likely dictate the habitat requirements of this animal but may in part be mitigated by the hydrophilic properties of elephant integument.
