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Snakes

Thanks, Climate Change: Rattlesnake Bites Are Likely to Get More Common

Warm summers mean more snakes, and more people outside mean more encounters. Here's what to do if you get bitten,

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Twice a month, Dr. Christopher Tedeschi answers your questions about wilderness first aid. Sign up for Outside+ today and get access to everything we publish. 

In the wake of a scorching summer across the western US, and with evidence of a warming climate everywhere, we may be at the beginning of a golden age for rattlesnakes. 

Although there may be some evidence that rattlesnakes are biting more humans than ever, there’s no clear trend. Reports from the 2021 season are incomplete, but early indicators suggest that the number of bites this year has remained stable. 

In the Pacific Northwest, poison center reports even modestly decreased from last year. “I’m actually surprised at the numbers,” says Courtney Temple, a medical toxicology fellow and emergency physician at Oregon Health & Science University. The Oregon Poison center took 28 calls for rattlesnake bites from January to August of 2020, but as of August 20 this year, had logged only 19. This year’s record-breaking heat wave may have had something to do with the smaller number of bites.

“It was pretty unmanageable during the day,” says Temple. “I’m wondering if that kept people inside.” 

Data from the Southwest seem similar. Halfway through 2021, Arizona had logged around 81 bites, compared with 105 for the same period last year. At least through 2020, though, the nationwide number has been somewhat flat. 

(Photo: Fabian Krause / EyeEm via Getty)

“It does look like the trends since 2017 have been rock solid in terms of rate of rattlesnake bites,” says Steve Dudley, the director of the Arizona Poison and Drug Information Center.

Nonetheless we can probably expect growing snake populations—and therefore bites—as the climate warms. A recent study on the impact of climate change on rattlesnake populations in the journal Ecology and Evolution suggests that “snakes will be able to emerge from overwintering earlier in the year and, in turn, wait until later months before going back into hiding.” More active time means more breeding, and more snakes.

A longer season would increase exposure to hikers (and pets), who should remain vigilant. Despite the fact that 25 percent or more of pit viper bites may be “dry bites”—in which no venom is transferred — the best move after any potentially venomous bite is evacuation. “Until you’re able to get to a health care facility after having a bite,” says Temple, “we can’t tell whether it’s a dry envenomation or a very concerning exposure. Keep the area below the level of the heart until we can assess whether or not you need antivenom.” 

Trying to capture the snake is generally unwise, she adds. 

“Do not prioritize trying to capture the snake, or try killing the snake — let the snake go, says Temple” Instead, try to remember the snake’s coloring or head shape and whether it had a rattle. Details may help experts decide about antivenom, which saves lives and limbs but can cost tens of thousands of dollars per treatment. 

Christopher Tedeschi teaches and writes about wilderness and disaster medicine. He is associate professor of emergency medicine at Columbia University and an editorial board member for the journal Wilderness and Environmental Medicine. He enjoys hiking and biking near his home in the lower Hudson Valley. 

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