In my home state of Pennsylvania, everyone has either hit a deer with their vehicle or knows someone who has. The Keystone State was identified as “high-risk” in 2024 by State Farm, with the likelihood of hitting a deer at 1 in 61, twice that of the national average. Deer vehicle collisions (DVCs) are all too common in many parts of the country, and unfortunately deer have proven quite resistant to our mitigation efforts.
State after state has researched ways to keep deer out of roadways or give them more warning signs that a vehicle is approaching, but DVCs continue to be a major issue. While we continue to learn more about influencing deer behavior, changing our own behavior can also work, and it helps to understand the most common factors influencing the rate of DVCs. Here are the top three.
Breeding and Fawning Seasons
Statistics show DVCs occur more frequently in months when rut activity (fall) and fawning (spring) are occurring. There is such a strong correlation, a study done in Ontario used DVC data as a proxy to determine when the rut was occurring. The Georgia Department of Natural Resources also uses their reported DVCs to create a peak rut map each year. Similarly, over half of reported crashes in Iowa occurred during peak deer breeding season from October to December. Both bucks and does increase their movement rates during the rut, so DVCs involve both sexes.
The fawning season also increases the likelihood of DVCs. As the time for birth nears, does seek quality fawning cover in areas away from other deer, so they move more and move out of their familiar core areas. Later, fawns that are old enough to flee from danger may end up crossing unfamiliar territory like roads or yards. They may be slower or more erratic when crossing a busy road.
Weather and Day Length
Seasonal changes can affect DVCs in some regions. In the late fall/early winter in northern states, as forage options decrease, deer may begin to travel in large groups towards wintering areas or “deer yards.” In northern states like New Hampshire, deer may travel 20 miles or more to their wintering area. This means there could be deer crossing roads they do not frequently use during warmer months, and drivers may not be used to watching for wildlife crossings.
Drivers also may be caught off guard in winter as the photoperiod (length of daylight) changes. For example, imagine your commute home from work always starts at 5:00 p.m. In spring and summer, the sun will still be relatively high during your commute, and it is less likely you will see deer crossing roadways during your drive home. As day length shortens in winter, daylight starts to slip away as early as 4:15 p.m., which means higher deer activity during your drive home at dusk.
In 2022, researchers at the University of Washington identified a 16% increase in DVCs after the end of daylight savings time in fall. They suggested that one benefit of permanent daylight saving time would be reduced DVCs.
Deer Population Density
Where deer population densities are higher, DVCs are likely to be more common, especially in suburban areas where roadways are more dense. A study on deer population dynamics at Iowa State found that deer density had a substantial impact on DVC rates. This is especially true in urban areas, as deer have less distance to roadways and industrial areas. The idea of deer density being correlated to DVC rate is further supported by this study published by the U.S. Fish and Wildlife Service.
Managed hunting in such areas, especially if it is focused on antlerless deer harvest, can reduce deer density to manageable levels and decrease the frequency of DVCs.
Avoiding Deer-Vehicle Collisions
Knowing about the factors above can help you more effectively avoid a deer-vehicle collision. Available scientific research and knowledge of deer biology also give us several active strategies for reducing your chances of colliding with a deer. Watch the NDA video above to learn about eight of those strategies.