Deadlier Than Sharks: The Science of Deer in the Headlights

Deadlier Than Sharks: The Science of Deer in the Headlights
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Spring: a beautiful time of year. When temperatures creep above freezing, rains refresh the landscape, and flowers start to spurt from the ground, puncturing the drab uncovered as the snows of winter recede. Wildlife also starts to emerge. For drivers, that means headaches.

As animals take to the skies and pastures, many sidetracked by the primordial urges of mating, they also inadvertently make their ways onto roadways, waterways, train tracks, and runways, and thus into the path of oncoming vehicles. Estimates suggest that billions of vertebrates are killed each year in these collisions.

Deer are the primary concern. Up to 1.5 million cars collide with deer annually in the United States, killing more than 200 Americans, causing approximately 10,000 injuries, and resulting in almost a billion dollars worth of damages.

By those numbers, deer are roughly two hundred times deadlier than sharks (though the comparison isn't exactly apples to apples).

On average, more collisions with deer occur in November, during mating season, but springtime is up there, too. Starting in May, mother deer will be tailed by one to three fawns. Problems arise when the families decide to cross treacherous rural roadways, especially in the evening.

Why are deer the poster children for animal-automotive collisions in the United States? The simplest explanation is that they are large in size, abundant, and widespread. As many as 30 million of the 100 to 300-pound mammals reside in the U.S., ranging from Maine in the Northeast, to Florida and Texas in the South, to Idaho in the West.

For a more nuanced explanation, we can look to their behavior. According to Purdue University ecologist Esteban Fernandez-Juricic, when confronted with oncoming vehicles, deer rely on anti-predator instincts. First and foremost, that means freezing -- the stereotypical "deer-in-the-headlights" response. In a normal predatory situation, this would allow them to avoid detection and gauge the situation. But while such a reaction is well suited to a gun-toting human or a lurking wolf, it is not at all useful when confronted with a one-ton hunk of metal traveling at 60 miles per hour. Often, a deer's decision to flee comes too late, if at all. The consequences to animal, car, and driver can be dire.

Yet despite the clear scope of the problem presented by the unfortunate interactions of deer and machine, the whole situation is relatively unstudied. Of course, a key problem is the question of how to study it.

Dr. Bradley Blackwell, a research wildlife biologist with the United States Department of Agriculture, plans to examine the problem using variables that we can control, namely, a vehicle's approach and speed. In a recently published review article, Fernandez-Juricic also noted that humans on foot tend to provoke greater alarm in deer than approaching vehicles do. Perhaps there's a way to make our cars more startling?

Until scientists discover a way to deer-proof our roadways, the best advice for avoiding them is to take it slow in rural, wooded areas in the evening hours, especially on winding roads with blind approaches.

Source: Lima SL, Blackwell BF, Devault TL, Fernández-Juricic E. "Animal reactions to oncoming vehicles: a conceptual review." Biol Rev Camb Philos Soc. 2014 Mar 25. doi: 10.1111/brv.12093.

(Images: Public Domain, Wikimedia Commons)

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