Meeting Abstract
There is growing evidence for mammalian herbivores that ambient temperature may interact directly with plant toxins in a way that the toxicity of plant defense compounds is amplified at warmer ambient temperatures. This phenomenon is known as temperature-dependent toxicity (TDT). We have been investigating TDT in an ecologically and evolutionarily relevant system of herbivorous woodrats (genus Neotoma) and their dietary toxins. Based on our previous work, we predicted that woodrats would have a lower tolerance for, and would thus ingest less, plant toxins at warmer temperatures. We measured tolerance for resin from creosote bush (Larrea tridentata) in the desert woodrat (N. lepida) at various ambient temperatures. We tested our hypothesis with wild-caught N. lepida from the Mojave Desert in lab-based feeding trials. We found that warm temperatures (28-29°C) significantly reduced the maximum dose of creosote resin (g ingested/day) ingested by woodrats compared to that observed at cooler temperatures (21-22°C; ANOVA, p<0.01). We also found that, when dose was held constant, woodrats at warmer temperatures reduced food intake and were unable to maintain body mass at warm temperatures compared to animals at cool temperatures (Kaplan-Meier, p<0.01). Our results demonstrate that tolerance to creosote resin in the desert woodrat decreases at ambient temperatures within the thermal neutral zone of N. lepida, temperatures that are well below heat stress for these mammals. The interactions of ambient temperature and plant toxins present a novel dimension to studies on herbivore foraging. Studying this interaction will advance the field of plant-animal interactions and may enable more accurate predictions of the responses of mammalian herbivores to climate change.
