California ground squirrels (Otospermophilus beecheyi) have an immunity to rattlesnake venom which they slowly develop as they become adults. Thus, adult California ground squirrels will fight off snakes to protect their pups from harm. However, when highly stressed, that immunity is lowered making them more susceptible to rattlesnake bites.

[Photo and caption by Chelsea Ortiz]

Holding, M. L., Putman, B. J., Kong, L. M., Smith, J. E., & 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.

Check out this Creature Feature by Neetha Iyer on California ground squirrels to find out more about their behavioral and physiological defenses against rattlesnakes (and other types of snakes).

[Edited by Maggie Creamer]