Rattlesnake Populations Could Explode as a Result of Climate Change

Rattlesnake populations could soar as a result of climate change, according to a study that was conducted by researchers at California Polytechnic State University and two conservation organizations.

"We are so used to climate change studies that forecast negative impacts on wildlife—it was interesting to see such starkly different findings for these snakes," corresponding author Hayley Crowell, a doctoral student in ecology and evolutionary biology at the University of Michigan, told Cal Poly News.

Found throughout the United States, rattlesnakes are most common in the Southwest. Thanks to heat-sensing organs couched in their heads, the snakes can hunt even in complete darkness, hence the designation "pit viper," according to the National Wildlife Federation. Though shy, they will not hesitate to attack if they feel threatened. Bites can cause extreme pain and even death in some instances, depending on the size of the snake and the availability of medical attention for the victim.

Like all reptiles, rattlesnakes are cold-blooded and they rely on external sources of heat such as the sun for warmth.

Published in the scientific journal Ecology and Evolution in May, the study suggests that some species may actually benefit from the numerically small but environmentally significant increase in ambient temperature that will occur over the next several decades. With some projections of increased temperatures between 2.5 and 10 degrees Fahrenheit in the next century, according to the Intergovernmental Panel on Climate Change, the increase could both inflate the number of months per year and the number of hours per day that rattlesnakes are active, providing them with more opportunities to breed.

"Specifically, snakes will be able to emerge from overwintering earlier in the year and, in turn, wait until later months before going back into hiding," the researchers wrote.

Furthermore, rattlesnakes are not likely to suffer from hunger or starvation. While rodent populations are expected to be negatively affected by climate change, potentially reducing the amount of prey available to apex predators such as rattlesnakes, the researchers found that the pit vipers channel their energy so efficiently that adult males can survive on as few as 500 or 600 calories annually. For comparison, that's equivalent to roughly half a "large burrito," according to Cal Poly News.

"Rattlesnakes require very little energy to exist," Crowell told Cal Poly News.

While the study results are specific to Pacific rattlesnakes, Crowell speculates that other generalist snake species, including garter snakes and water snakes, might also benefit from the effects of climate change. However, specialist ones might not fare as well.

"Other snake species, such as the high montane kingsnakes and rattlesnake species, may have a harder time as they are specifically adapted to cooler climates and, as they keep moving up in elevation to avoid a warming world, eventually they will run out of space to move up," she said. "It is also possible that specialized desert snakes may be in trouble as deserts may heat up beyond the toasty temperatures that these snakes prefer."

The study results could potentially forecast a surge in the incidence of human-rattlesnake encounters and bites. In 2019, the science news outlet Stat reported that snakebites are on the rise as snakes expand their range. However, Crowell, who states that envenomations and resulting injuries are already extremely few and far between, does not expect them to "greatly increase, if at all, in light of these discoveries. "For the most part," she told Newsweek, "we don't need to worry too much." Rather than further stoke ophidiophobia, or fear of snakes, she hopes that the study will prompt more nuanced consideration of the impact of climate change on animal species.

Update, 07/06/21: This article has been updated to include comments from Hayley Crowell.