Living amongst large predatory carnivores could actually make you safer. A study publishing in the Cell Press journal Current Biology on August 5 found that pumas—wild cats also known as mountain lions, cougars, or panthers—change deer behavior, leading to fewer collisions with cars on roadways. In areas where puma occupancy is high, the authors report a significant reduction in the total expected number of collisions over a 5-year period.
"We found that large carnivores can make roadways safer through their effects on prey behavior and space use," says lead author Justin Suraci of Conservation Science Partners in Truckee, California.
"Deer alter their use of both space and time where pumas are present, overlapping less with roads and reducing activity at night, when some of the most dangerous collisions occur," says Suraci. "Increased road safety thus represents an ecosystem service that large predators like pumas can provide to human communities."
The researchers were interested in quantifying these ecosystem services. While it has been suggested that predators of deer and other ungulates might cut down on car accidents, those dynamics had not been clearly shown or quantified in places where large carnivore populations are well established. Suraci and his colleagues studied a large camera trap dataset and spatial data on collisions between vehicles and wildlife to explore pumas' effects on their prey's behavior and the implications for human drivers across the Olympic Peninsula of Washington, USA.
"It's important to remember that large carnivores, like many wildlife species, can only persist if they're able to share landscapes with people, which in many cases may require us to change our behaviors and attitudes to make coexistence possible," Suraci says.
The researchers found that, where pumas are present, deer are more active during the day. They were also 15% less likely to be in areas with lots of roads, choosing instead to spend more time in remote habitat areas.
As a result of those changes in deer activity, the researchers calculated a 67% reduction in the likelihood of a deer-vehicle collision. They also estimated a 76% reduction in the expected number of collisions between vehicles and deer over 5 years. Tracking collar data showed an increase in car accidents with deer during the day instead of at night, when those accidents tend to have worse outcomes.
"Deer try to avoid risk from pumas and, in doing so, spend less time near roads and are involved in fewer collisions," says Suraci. "Carnivores may well be providing a similar road safety service elsewhere around the globe where populations have persisted and this valuable ecosystem service has just gone unnoticed to date."
By shedding light on these dynamics, the researchers hope that more people may begin to realize the benefits of living among large carnivores. "This may be especially true for the eastern US and Canada, where pumas are slowly, naturally recolonizing, and there are ongoing discussions about a potential reintroduction program," says Mark Elbroch of Panthera in New York City.
"While wildlife have inherent value outside of the benefits they provide to humans, a clear articulation of those benefits, such as increased road safety as a byproduct of natural predator-prey interactions, can, I believe, provide a very valuable tool to help increase tolerance for predatory wildlife and encourage the behavioral changes that coexistence requires."
"When we talk about pumas, we often focus on the risks they pose. But we rarely stop to consider the many ways they benefit us as well," Elbroch says. "Living alongside large carnivores isn't simply about protecting wildlife; it's about protecting the many ways they quietly benefit us every day."
