UC San Diego

Due to the requirements for living in an extreme habitat, animals in desert ecosystems are experiencing significant deleterious effects from climate change, including those that impact their food availability. Conventional wisdom within ecology indicates that dietary generalists are more adaptable to the threats inherent to environmental changes than specialists. To better understand the potential for certain desert species to adapt to continual habitat alteration in the face of ongoing climate change, we used stable isotope analysis to investigate the degree to which members of a desert food web are potentially dietary generalists vs. specialists. We measured stable carbon and nitrogen isotope values from a top predator, sidewinder rattlesnakes (Crotalus cerastes), and several of their potential prey, including carnivorous lizards and granivorous rodents that have long been considered dietary specialists. Our stable isotope data indicate that a number of lizards were likely carnivorous as expected from previous research, whereas Yuman Desert fringe-toed (YDFT) lizards (Uma rufopunctata) and desert kangaroo rats (Dipodomys deserti), previously thought to be strict insectivores and seed-eaters, respectively, demonstrate stable isotope values more in alignment with those of generalist omnivores. In addition, we did not detect a shift in diet from lizards to rats with age as has been hypothesized for sidewinder rattlesnakes, but the isotope values from the YDFT lizards and rats overlapped significantly, hampering our ability to detect significant changes in snake diets over time. Our study provides valuable insights into the dietary niches and trophic relationships of several important desert species, which can be valuable for navigating animal and habitat conservation and management needs as we continue understanding the long-term impacts of climate change on extreme desert habitats.