Saturday, June 15, 2013

Good Friends and Snake Venom

My good friends, Matt Holding and Sloan Henningsen, paid a visit to our field site last week. Matt and I know each other from working in Dr. Emily Taylor’s lab at Cal Poly. Sloan is his awesome significant other and they make quite a terrific field team. Matt is now a Ph.D. student in the Gibbs Lab at The Ohio State University and we are collaborating on a project examining squirrel venom resistance and rattlesnake venom toxicity.

Many people do not know that ground squirrel blood contains proteins that neutralize rattlesnake venom. This means they can fight off the effects of envenomation, but are not immune (like how your body can fight off a cold). The level of resistance in squirrels correlates with blood volume – therefore pups are more susceptible to death by envenomation than adults. It was long thought that adults were essentially free from rattlesnake predation because of their resistance, but our research has shown that adults are commonly preyed upon by snakes.

Images of rattlesnake bite wounds from two different populations of ground squirrels. The top image shows the wound (circled in white) of a California ground squirrel with venom resistance. The bottom image show a wound caused by the same amount of venom in a squirrel without venom resistance.** 

For his dissertation, Matt is examining venom resistance in several populations of California ground squirrels.  My field site at BORR is one of the populations he is sampling from.  We are excited to see the composition of rattlesnake venom in relation to squirrel blood resistance especially since adult squirrels are eaten by snakes at our site. We are also interested in examining the individual variation in resistance (how resistance differs from squirrel to squirrel) and if this variation correlates with squirrel anti-snake behaviors (tail-flagging, alarm calling, substrate throwing, etc.).

Matt demonstrated several of his extraction methods while he visited us. Please enjoy the pictures below. Also, check out his awesome blog here.

 We scare a trapped squirrel into a bag

 Matt puts the squirrel under using a light anesthetic 

I measure various body parts on the squirrel

 Matt tubes a rattlesnake

We draw blood from the snake 

 Matt collects its venom (you can see some in the bottom of the glass)

**Image from: Owings, D. H., and R. G. Coss. 2007. Hunting California Ground Squirrels: Constraints and Opportunities for Northern Pacific Rattlesnakes. Biology of the Rattlesnakes.

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