There are many obstacles and surprises to keep an eye out for while driving, but one animal is actually helping drivers in an unexpected way. A recent study conducted by a wild cat conservation organization found that mountain lions make roads safer simply by living in the area.

The presence of mountain lions, which are also called cougars and pumas, led to a 76% decrease in deer-vehicle collisions on Washington’s Olympic Peninsula. Biologists found that deer activity began to change in response to the predators’ activity, ultimately making them less of a threat to drivers, especially at night.

The study, which was published on August 5 in Current Biology, compared 5 years of traffic and crash records from across the Olympic Peninsula with data from over 500 camera traps and collars on 59 cougars from Panthera’s Olympic Cougar Project. Data showed that a healthy carnivore population reduced deer-vehicle crashes not because of overhunting, but because of changing prey behavior.

Mountain Lions & ‘Top-Down’ Ecological Regulation

Mountain lions and other large carnivores who are at the top of the food chain actually play a massive role in regulating other species’ populations within their ecosystem. This is called ‘top-down’ regulation, and it describes how a predatory species exerts control over its prey population, and so on down the food chain.

This study’s data is a prime example of top-down regulation in action. With a healthy and active puma population, deer in Washington began to become more active at different times of day and move to other areas. In fact, deer wer 15% less likely to use high-road density areas where pumas were also present.

How Mountain Lions Make Roads Safer

Not only were deer less likely to stay in areas near roads when cougars were present, but they were also 86% more likely to choose less-developed areas away from roads altogtether.

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Mountain lions also encouraged the deer population to change in another fascinating way. Because these wild animals are crepuscular, meaning they’re most active at dawn and dusk, deer activity began to shift to the middle of the day. Even though more deer-vehicle collisions began happening during the day in areas where pumas were active, fewer of these accidents occurred at night, when drivers are at a visual disadvantage.

Overall, this study found a “67% reduction in the probability of a deer-vehicle collision and a 76% reduction in the total expected number of collisions” in the areas of the Olympic Peninsula where cougars were most active.

Although this study is the first of its kind, it suggests that a healthy population of wild cats and other large predators can benefit everyone in the ecosystem, including humans. This timely news comes at a time when several states are considering reintroducing mountain lions, and these findings should certainly be taken into consideration when making such an important decision.