SORENSEN, JS; MCLISTER, J; DEARING, MD: The impact of dietary toxins on locomotion in mammalian herbivores

Ingestion of plant secondary compounds is a physiological challenge for mammalian herbivores. The detoxification of plant secondary compounds can impose severe energy constraints via increased metabolic demands and energy excretion as well as decreased energy intake. We hypothesized that the energetic consequences of consuming plant toxins will significantly compromise energy allocated to locomotion in mammalian herbivores. Furthermore, we predicted that foraging strategy would influence the degree to which consumption of secondary compounds impacts energy allocation such that locomotion of dietary specialists would be less impacted than generalists when both are exposed to the toxic diet (juniper) preferred by the specialist. We tested these hypotheses by comparing distance run, time run, and maximum speed of a dietary specialist () and generalist () on control diets and diets containing one seeded juniper (). We also compared basal metabolic rates of the two species on control and juniper diets. We found that generalists significantly reduced daily distance and time spent running when consuming juniper diet versus control diet. The locomotor activity of specialists was unaffected by diet. Metabolic rates increased in generalists consuming a juniper diet. The data suggest that foraging on a juniper diet compromises energy dependent activities of generalist woodrats. These data also suggest that the process of detoxification may elevate metabolic rates, thereby contributing to energetic constraints.