Meeting Abstract

9.3  Saturday, Jan. 4 08:30  The Effects of Ambient Temperature on Toxin Tolerance in Mammalian Herbivores KURNATH, P.*; DEARING, M. D.; University of Utah, Salt Lake City; University of Utah, Salt Lake City patrice.kurnath@utah.edu

Intrinsic factors such as plant toxins and nutrients are well known to influence diet selection in mammalian herbivores, yet extrinsic factors like ambient temperature have received less attention. There is growing evidence that plant secondary compounds (PSCs) become more toxic at elevated ambient temperatures due to decreased liver function by the herbivore. This phenomenon, known as temperature-dependent toxicity, could have critical implications for mammalian herbivores that must balance the physiological functions of homeothermy and PSC detoxification. Here, we investigated how ambient temperature affects the maximum tolerable dose of PSCs in the desert woodrat, Neotoma lepida. Based on our previous work, we predicted that woodrats would have a lower maximum tolerable dose for PSCs and would therefore ingest fewer PSCs at warmer temperatures. Wild caught N. lepida (N=20) from the Mojave Desert were acclimated to one of two ambient temperatures (warm=29°C, cool=21°C) for 30 days before a 21 day feeding trial. Woodrats were given diets containing resin from creosote bush leaves (Larrea tridentata), which comprises most of their native diet and is high in PSCs. Body mass, food intake and resin intake were recorded daily. The maximum tolerable dose was defined as the greatest amount of resin ingested over a 24 hour period for each animal. Warm-acclimated woodrats had a significantly lower maximum tolerable dose of creosote resin compared to cool acclimated woodrats (ANOVA, p<0.01). The maximum tolerable dose for warm-acclimated woodrats was 69% that of cool-acclimated woodrats. These results suggest that the amount of creosote resin woodrats can consume is substantially limited by warmer ambient temperatures. Our results also could have adverse implications for mammalian herbivores in a warming climate.