Cougars Reduce Deer-Vehicle Collisions by Up to 76%

The presence of cougars in a landscape can have a significant impact on the behavior of deer, leading to a reduction in deer-vehicle collisions. According to a new study, the expected number of deer-vehicle collisions fell by 76% over five years in areas where cougars were highly active. This reduction in collisions is not due to the cougars eating more deer, but rather because the deer change their behavior to avoid areas where cougars are present.

## The Landscape of Fear The study found that the presence of cougars creates a "landscape of fear" that pushes deer away from developed areas and shifts their active hours from nighttime to daylight. This change in behavior is driven by the deer's fear of being preyed upon by cougars, rather than a reduction in deer numbers. The study's lead author, Mark Elbroch, notes that the deer know where they are most likely to be at risk of an encounter with a large carnivore, and they avoid these areas more.

## The Impact on Deer Behavior The study analyzed data from 503 camera locations and 59 collared pumas, and found that deer were 15% less likely to occupy areas with a high density of roadways when pumas were present. They were also 86% more likely to reside in remote areas, far from development. Additionally, the deer shifted their daily schedules to daylight hours, becoming less active at night. This change in behavior is likely due to the fact that pumas are crepuscular and nocturnal, and are most active at dawn and dusk.

## The Broader Implications The study's findings have important implications for wildlife conservation and road safety. Glen Kalisz, a habitat connectivity biologist, notes that the reduction in deer-vehicle collisions is not just due to the presence of cougars, but also because the deer are changing their behavior to avoid areas where cougars are present. This highlights the importance of considering the complex interactions between predators and prey in conservation efforts. The study also suggests that cougars may be indirectly protecting humans from disease, such as chronic wasting disease, which is present in Washington State.

The study's results are presented in the following table: | Area | Expected Number of Deer-Vehicle Collisions | Probability of Collision | | --- | --- | --- | | High cougar activity | 24% of expected collisions | 33% of probability | | Low cougar activity | 100% of expected collisions | 100% of probability | | Overall reduction | 76% reduction | 67% reduction |

Overall, the study highlights the importance of coexisting with large carnivores, such as cougars, and considering the complex interactions between predators and prey in conservation efforts. By understanding how cougars impact deer behavior, we can better manage wildlife populations and reduce the risk of deer-vehicle collisions.