Wednesday, November 28, 2007

The Best Offense is a Good Defense

Ground squirrels have gone through a sort of evolutionary arms race with rattlesnakes. Due to heavy predation of ground squirrels by rattlesnakes, the squirrels have evolved blood proteins that help their body neutralize the snake’s venom, helping prevent sure death from the poisonous snake. In addition to this adaptation, ground squirrels studied by Aaron Rundus at the University of California, Davis, have been found to be the first animals to use infrared signals to ward off predators.

When squirrels find a snake lurking, looking for a meal, they harass the snake by teasing it and whipping its tail around. Rundus used infrared videotape of the squirrels caged with different snakes in the lab, and observed any differences. He was surprised to find when the squirrels were harassing the rattlesnakes, they heated their tails up to 2° C at the base and at the tip. This was odd due to the tail usually being cooler than the rest of the body, but the warmer tail is beneficial to the squirrels when trying to deter the being a meal due to the rattlesnakes’ use of infrared sensors to locate prey. The most interesting observation was the infrared video of the squirrels performing the same behavior with gopher snakes. The gopher snakes, which do not use infrared to pinpoint prey, did not elicit the same reaction with squirrels, and they tail was shown to raise only 0.2° C during the behavior.

From the outside, it would seem squirrels are being quite brave when they harass snakes, but in actuality, adult ground squirrels are very well adapted to deal with this venomous predator and even use the snakes hunting senses for its own benefit.

Posted by Courtney Huffman (10)



At 9:23 PM, Anonymous Anonymous said...

This is a very interesting article! I was not aware that ground squirrels have developed blood proteins and infrared signals against snakes. This example goes to show you that species are becoming more adapted to their environments in this day and age. With such well adaptations dominating future populations could we see a decline in the snakes and other predators, now that their prey’s are unaffected by their poisons and presence? Just a thought to think about!

Posted By: Rachel McMahon (10)


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