California ground squirrels acquire resistance to rattlesnake venom throughout their lifetime; however, stress (measured as glucocorticoids) lowers this resistance and also changes the behavior of squirrels around snakes. For instance, squirrels who had higher glucocorticoids would spend a longer time waiting to feed while near a rattlesnake.

Art by Nora Prindle, @Noraprindle.art, fact by Chelsea Ortiz-Jimenez

[Edited by Isabelle McDonald]

Reference:

Holding, M. L., Putman, B. J., Kong, L., Smith, J. A., & Clark, R. W. (2020). Physiological Stress Integrates Resistance to Rattlesnake Venom and the Onset of Risky Foraging in California Ground Squirrels. Toxins, 12(10), 617. https://doi.org/10.3390/toxins12100617