Ambient temperature and toxic diets constrain snake venom resistance in a desert rodent.

Variation in ambient temperature and food availability is commonplace in nature and likely exerts several types of eco-evolutionary pressures that mediate species' interactions. In predator-prey interactions between snakes and rodents, the molecular interface is formed by snake venom and mammalian venom resistance proteins. However, the abiotic factors modulating resistance are poorly understood. Here, we measured serum-based venom resistance of desert woodrats (Neotoma lepida) maintained at either cool or warm ambient temperatures and fed creosote bush resin (native diet) or a control diet. Woodrat serum was collected and tested for its ability to inhibit the activity of rattlesnake venom metalloproteinases. Woodrats raised at cooler temperatures, as well as those consuming diets with creosote resin, were significantly less able to inhibit snake venom, suggesting that they would be more susceptible to snakebite. These results suggest that temperature and dietary variation across the distribution over which these rattlesnakes and woodrats interact could structure the outcomes of these predator-prey interactions. Additionally, these results may help explain why ambient temperatures, rather than dietary differences, predict the presence of neurotoxic versus proteolytic venom phenotypes in some rattlesnake species.