As the Earth's climate changes over the next century, rattlesnakes will have to adapt as much as 1,000 times more quickly than they have in the past to find habitats that they can tolerate.
Some species may be flexible enough to handle the rapidly changing conditions. But many will be unable to slither away fast enough to survive. And the same is likely true for other kinds of creatures, including mammals and other reptiles.
"I'm not sure how species will be able to follow the climate so quickly," said Michelle Lawing, a paleobiologist at Indiana University in Bloomington. "In some cases, it might be better for conservationists to move them or create managed corridors where they could be assisted to better, more suitable habitats."
"Even when we make a big effort, the world will still look very different," Lawing added. "We're going to have different combinations of species in different places that we've never seen before."
To predict where animals might be able to live in the coming decades, plenty of studies have taken into account the physical traits of various species and how those traits might limit their future ranges.
To add more context to these kinds of projections, Lawing and colleague David Polly looked to the past to see how rattlesnakes have adapted to previous climate shifts. They chose to study rattlesnakes because these reptiles have lived and moved throughout North America for a long time.
For the first part of the study, the researchers used evidence from fossils and elsewhere to create maps of the ranges of 11 rattlesnake species at 4,000-year intervals over the past 320,000 years. Then, they analyzed all sorts of details about each era's climate conditions, including things such as mean annual temperature and maximum temperature of the warmest quarter of the year. That allowed them to see how temperature and precipitation has affected the suitable ranges of the snakes over the millennia.
In the past, rattlesnakes have responded to changes in climate by moving to new places. Those geographic movements happen 100 to 1,000 times faster than the animals can adapt to physically. In the face of major climatic changes, in other words, evolution is not an option. And the snakes won't be able to move fast enough to get to a new, more habitable place.
The researchers used accepted climate projections from the Intergovernmental Panel on Climate Change to look at how climate changes might affect rattlesnakes through the year 2100.
Their results, published in the journal PLoS One, showed that rattlesnakes are going to have to move an average of between 100 and 1,000 times more quickly than they have over the last 300 millennia to reach acceptable places for them to survive. And that's without threats from predators, competitors, parasites, human developments and other obstacles.
"Based on what they've been doing over the past 320,000 years, they probably cannot adapt that quickly in 90 years to different climate tolerances," Lawing said. "They will have to physically move."
Even though rattlesnakes are often vilified, they play important roles in the ecosystems where they live, said Jesse Meik, an evolutionary biologist at the University of Texas, Arlington.
The new study adds insight into what the future holds for these and many other animals that are sensitive to changes in climate, he added. Some species may be able to physically adapt, but some will likely need to shift their home ranges to avoid extinction, and that might not always be possible.
"This study is special in that it takes data from the past and present — and not just the present — to make inferences about the future," Meik said. "This is an important development given that inferences about the future are by definition clouded by uncertainty."
"We can probably expect this type of result from all kinds of groups," he added. "I would say that it is not surprising that the results indicate that climate change will happen too quickly for rattlesnakes to deal with, given the magnitude of predicted climate change."