Journal of Chemical Ecology

, Volume 31, Issue 11, pp 2501–2518 | Cite as

California Ground Squirrel (Spermophilus beecheyi) Defenses against Rattlesnake Venom Digestive and Hemostatic Toxins

  • James E. Biardi
  • David C. Chien
  • Richard G. Coss


Previous studies have shown that some mammals are able to neutralize venom from snake predators. California ground squirrels (Spermophilus beecheyi) show variation among populations in their ability to bind venom and minimize damage from northern Pacific rattlesnakes (Crotalus oreganus), but the venom toxins targeted by resistance have not been investigated. Four California ground squirrel populations, selected for differences in local density or type of rattlesnake predators, were assayed for their ability to neutralize digestive and hemostatic effects of venom from three rattlesnake species. In Douglas ground squirrels (S. b. douglasii), we found that animals from a location where snakes are common showed greater inhibition of venom metalloprotease and hemolytic activity than animals from a location where snakes are rare. Effects on general proteolysis were not different. Douglas ground squirrels also reduced the metalloprotease activity of venom from sympatric northern Pacific rattlesnakes (Crotalus oreganus oreganus) more than the activity of venom from allopatric western diamondback rattlesnakes (C. atrox), but enhanced fibrinolysis of sympatric venom almost 1.8 times above baseline levels. Two Beechey ground squirrel (S. b. beecheyi) populations had similar inhibition of venoms from northern and southern Pacific rattlesnakes (C. o. helleri), despite differences between the populations in the locally prevalent predator. However, the venom toxins inhibited by Beechey squirrels did vary among venom from Pacific rattlesnake subspecies, and between these venoms and venom from allopatric western diamondback rattlesnakes. Blood plasma from Beechey squirrels showed highest inhibition of metalloprotease activity of northern Pacific rattlesnake venom, general proteolytic activity and hemolysis of southern Pacific rattlesnake venom, and hemolysis by allopatric western diamondback venom. These results reveal previously cryptic variation in venom activity against resistant prey that suggests reciprocal adaptation at the molecular level.

Key Words

Spermophilus beecheyi Crotalus oreganus Crotalus atrox venom natural resistance coevolution predator–prey 



This manuscript was greatly improved by the comments of two anonymous reviewers. J.E.B. was supported by a Floyd and Mary Schwall Dissertation Fellowship in Biomedical Research.


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Copyright information

© Springer Science + Business Media, Inc. 2005

Authors and Affiliations

  • James E. Biardi
    • 1
  • David C. Chien
    • 2
  • Richard G. Coss
    • 2
  1. 1.PROF Postdoctoral Program and Department of ChemistryUniversity of CaliforniaDavisUSA
  2. 2.Department of PsychologyUniversity of CaliforniaDavisUSA

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