The cost of too many deer

In Wisconsin, we know all too well the perils of the deer population, especially on country roads at night. An estimated one million deer-vehicle collisions (DVCs) occur every year in the United States, causing 20,000 injuries, 200 fatalities, and $9 billion in economic losses. AAE grad student Jennifer Raynor seeks to estimate the causal impact of changes in deer abundance on roadway collisions and associated economic losses.

Jennifer is analyzing the data to identify the effects of white-tailed deer (Odocoileus virginianus) abundance, traffic volume, land cover, and weather on the frequency of county-level DVCs in Wisconsin between 1998 and 2013.  Results show that a 1 percent increase in deer abundance leads to a 0.3 percent increase in DVCs.

One additional deer above the county-year average causes $30 in economic losses from DVCs each year. Equivalently, 301 additional deer cause one more DVC per year. Achieving the latest post-hunt population goal would reduce DVC losses by an estimated $23.3 million annually, roughly equal to hunting license and permit revenues.

Looking forward, DVCs losses likely will continue to grow. Cultural shifts in driving or development patterns are unlikely, so only deer abundance provides a plausible leverage point for broad-scale DVC mitigation. The results suggest that a relatively small decrease in the deer population could help to decrease DVCs.