Despite their Disney-branded charms and generally decent nature, deer have no regard at all for traffic laws. That—coupled with a tendency to trot along rural roadways—leads to roughly 1.2 million collisions with automobiles every year, with 200 of those ending in a human fatality. In fact, deer are the most dangerous large animal in North America to humans, say the authors of a new study. They argue that the solution may be to introduce a less adorable animal into the equation: the cougar.

A paper [PDF] co-authored by University of Idaho wildlife ecologist Sophie Gilbert and recently published in the journal Conservation Letters argues that a restoration of the cougar population in 19 states in the eastern U.S. could lead to 21,400 fewer injuries and 155 fewer deaths over 30 years.

In order to assess what this modified food chain might do, the authors estimated that roughly 850 square miles would be needed in order for cougars to flourish to the point where they would be able to sustain life and control the local deer population. Over a six-year span, a cougar might kill 259 deer. Even if most of those were, as the study speculates, already sick or dying, it would still be enough of a rampage to affect the number of deer wandering into roads and subsequently injuring drivers in collisions.

The authors don’t know if the scenario they present would be similar if humans were to introduce cougars as opposed to the species flourishing on their own, which they sometimes do. Consider South Dakota: An increase in the number of cats there has led to a $1.1 million reduction in annual collision costs. (This population boom had a little help though: Cougars—also called mountain lions—were protected as a threatened species in South Dakota for more than two decades. Reclassified as big game animals in 2003, they're now hunted in the state.)

There’s also the troubling matter of cougars not limiting their diet to deer: As many as 30 human deaths, or one a year, might result from their repopulation. Some have been sighted as far east as Connecticut.

[h/t New York Times]

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