Large predators can make people safer by reducing the number of road accidents involving collisions with deer. A study in Washington state has shown that the presence of cougars led to a 76 per cent reduction in the number of such accidents.
鈥淚 think that this road-safety benefit could be playing out in many other places,鈥� says of the non-profit Conservation Science Partners. 鈥淭hat鈥檚 just one of several ecosystem services that these large carnivores provide.鈥�
A 2021 study in Wisconsin found that the return of wolves to a county , providing economic benefits 63 times greater than the costs of wolves killing livestock. These reductions were due to changes in deer behaviour, as well as deer numbers falling due to predation by wolves, the study concluded.
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Now Suraci and his colleagues have looked at what鈥檚 happening on the Olympic Peninsula in Washington state, where there鈥檚 a stable population of cougars 鈥� also known as pumas 鈥� and deer. 鈥淲e worked with Native American communities, who are running their own wildlife monitoring programs,鈥� he says.
More than 500 camera traps have been set up as part of these programs, and nearly 60 cougars were collared. This allowed the researchers to see where and when deer and cougars were present. Their analysis shows that deer avoid road edges and the margins of towns and cities when cougars are present, making them less likely to be hit by cars or trucks.
鈥淭hose habitat edges are the best hunting habitat for pumas. They can hide in the forest and attack a deer foraging along the roadside,鈥� says Suraci. 鈥淪o what we think is happening is that deer are moving away from these more fragmented, edgy areas with higher road density where the pumas are present.鈥�
When cougars were present, deer were also less active at night and more active during the day. This is likely a response to the fact that cougars hunt mainly at night, and may also have contributed to the reduction in accidents.
This is an example of a 鈥渓andscape of fear鈥� in action, says at Western University in Canada. 鈥淭his is an excellent paper. It provides many compelling lines of evidence that paint a clear picture 鈥� that large carnivores benefit society. The authors beautifully demonstrate that the mere presence of large carnivores can reduce vehicle collisions with deer.鈥�
鈥淭hat is good news all around,鈥� she says. 鈥淎s though that weren鈥檛 enough, cougars also provide this service completely free of charge.鈥�
Suraci also thinks this will be generally true for large predators. Discussions about the reintroduction of large predators tend to focus on the negative aspects, such as the killing of livestock, he says. But many benefits often aren鈥檛 obvious.
For instance, large predators may also reduce the damage deer do to crops and gardens, and the spread of diseases .
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