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Frost bites

How western rattlesnakes cozy up during winter

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Indiana Jones might not mind getting trapped in a snake den if he were in Montana. Of the 10 species of snakes found in the state, only one is poisonous: the western rattlesnake (Crotalus viridis). And even if Dr. Jones stumbled into a Montana rattler den, the odds of him receiving a fatal bite are much lower than if he were in one of the North African viper pits from which he usually needs to escape.

Victims of rattlesnake bites develop extreme soreness in the bite area, nausea and vomiting. The bite can lead to gangrene and the amputation of a limb, but rarely to death, unlike cobra bites, which affect the nervous system and cause heart failure.

Luckily, of the hundreds of thousands of hikers, hunters and others who have ventured into Montana’s backcountry over the last decade, only a half-dozen have been bitten by a rattler, and none have died. During the winter, the odds are virtually zero of encountering these shy, well-camouflaged slitherers.

Montana Headwall
  • Ronan Donovan

“You would need a backhoe to uncover a den,” says James E. Knight, a wildlife specialist at Montana State University in Bozeman. “They are not easy to get to in the rock.”

Rattlesnake dens, also called hibernacula, are typically located on rocky, south-facing slopes. “Western rattlesnakes don’t dig,” Knight says. “They use an existing hole or spaces under rocks, and they generally return year after year. Rattlers have a small range, about 10 acres.”

Rattlesnakes den to conserve body heat, and they often share the space with other snake species. The protection of a den “slows the rate at which their temperature drops and keeps them from freezing, but eventually they get real cold, reaching equilibrium with the ground around them,” Knight explains.

As their body temperature drops, rattlesnakes move with much less vigor, which makes winter a good time for scientists to extract their venom through a technique called milking. The process involves a trained expert holding the animal firmly behind its jaws to control its head and to open its mouth. With the snake’s fangs hanging over a small glass vial, the milker squeezes the snake around the back of its head, triggering the venom gland above its upper jaw to release the yellow toxic substance into the vial. It’s a risky process, not one to try at home.

Rattlesnake venom is most commonly used to make antivenin, but the pharmaceutical industry is exploring other potential medicinal uses. Snake venom contains a number of enzymes, proteins and other chemicals linked to possible cures for diseases, including breast cancer and hypertension. But not all snake venom is the same. Rattlesnake venom has shown its greatest promise in the treatment of high blood pressure, as a bite from this belly-crawler attacks the cardiovascular system.

Such potential could be enough for even the biggest ophidiophobe, like Indiana Jones, to reconsider his fear and loathing of snakes.

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