David Gorchov was a new driver, 17 years old, when he hit a deer in New Jersey. "It was a pretty traumatic experience," he said. Decades later, Gorchov is a professor of biology at Miami University in Ohio, and white-tailed deer sit at the center of his research, including the question of why there are so many of them.
Collisions like his are common. State Farm estimates there were more than 1.6 million animal-vehicle collision claims in the U.S. between July 1, 2025, and June 30, 2026, and the insurer paid $1.9 billion in claim costs over that period. Deer remain by far the most frequently struck animal, according to State Farm, and collisions happen more often in the fall, when deer are more active. State Farm ranks November, October and December, in that order, as the top months for collisions with large animals. The crashes can be deadly. Deaths from collisions with animals rose from 89 in 1975 to 210 in 2024, according to the Insurance Institute for Highway Safety, and 73 people died in such crashes in Ohio from 2015 through 2024.
In many areas of the East and the Midwest, Gorchov said, white-tailed deer are at much higher densities than scientists think they were before European colonization.
Gorchov, who chairs Miami University's Natural Areas Committee and studies how deer affect native forest plants and interact with invasive shrubs, explains to Campus Insights Media why deer populations have grown and where they thrive.
Why there are so many more deer today
Gorchov pointed to three reasons deer are so plentiful in so many places today.
- More food. Farm fields, lawns and gardens, mature forests, young woods regrowing on once-cleared land and the edges where forest meets open field each offer deer different plants at different times of year. Together, they keep deer fed through the seasons.
- Natural predators are gone. Wolves and mountain lions, which once hunted deer, were exterminated.
- Many areas have no hunting. Within city limits, and often on private land, deer aren't hunted, so nothing replaces their natural predators.
A spring boost from an invasive shrub
Food is also at the heart of a less obvious part of the story. Amur honeysuckle, one of the bush honeysuckles, is a shrub native to East Asia that was brought to the U.S. in 1898 and has since spread into forests in Ohio and other states. It grows up to 15 feet tall, with white flowers and bright red berries, and it leafs out early in the spring and drops its leaves late in the fall. Deer in Gorchov's area eat a lot of it, he said. He and his students tracked deer browsing on Amur honeysuckle at all times of year and found a lot of browsing in early spring.
The timing matters. Protein is scarce for plant-eating animals, Gorchov said, and, in the early spring, when does are pregnant, with fawns developing, they need a lot of protein. Amur honeysuckle leafs out early, and leaves are higher in protein than stems. Native trees and shrubs are still bare then, so deer browsing on them get twigs with little protein. "So these shrubs provide a high protein input just at the time of the year that the does are really in need of high protein," Gorchov said.
Where deer thrive
Deer do best in a landscape that mixes forests, fields, lawns, suburbs and farmland, because it gives them a diversity of food sources, Gorchov said. Different foods are available at different times of year in each, and where those areas sit close together, deer can move between them to find high-quality food. "A lot of deer will spend the day in forests and at night come out into agricultural fields and into suburban gardens," he said.
What too many deer do to a forest
In 2010, Gorchov and his Miami colleague Tom Crist set up what they call deer exclosure plots, fencing some areas off from deer and leaving control plots where deer had access. Inside the fences, they found a pretty rapid recovery of tree seedlings.
Gorchov counts as a tree seedling any young tree taller than 30 centimeters (about a foot) but still slender, with a trunk less than an inch (about 2.5 centimeters) across at breast height, the 4.5-foot mark where foresters measure trunks. Healthy forest regeneration needs at least one seedling for every 4 square meters (about 43 square feet), he said. The forests in Miami's Natural Areas had less than that. Where deer were fenced out, the density has increased and is now above that threshold.
It is a very widespread problem, Gorchov said: Many parts of the Eastern and Midwestern U.S. have deer at very high densities, with impacts particularly on tree seedling growth and forest regeneration.
High numbers are not good for the deer either. Most people in southwest Ohio understand that high deer density is a problem, Gorchov said, but a few believe deer are better off at high density, "and that's not really true." Some deer diseases become a problem at high density, and deer can suffer from low nutrition. "So the deer typically are healthier when they're at lower density," he said.
Bringing the numbers down
Once the researchers found that the low density of tree seedlings and wildflowers was due primarily to deer, Miami developed a hunting program for its Natural Areas. The university's 2022 deer management plan called deer overabundance "an acute and increasing threat to tree and wildflower regeneration" in those forests. It also noted that reducing deer numbers would cut deer-vehicle collisions and the insurance and infrastructure costs that come with them. The program uses bow hunters. Starting in the winter of 2022-23, sport hunters have applied to hunt selected parts of the Natural Areas away from trails, and the program has been repeated every winter since. At the time of the interview, Gorchov said four years of hunting had lowered deer density, based on estimates from counts of deer pellets.
Reducing deer numbers more broadly is going to require hunters taking does, he said. The number of fawns born each year depends on how many does there are. The number of bucks does not affect the birth rate.
States where drivers face the highest risk
West Virginia drivers have the highest likelihood of an animal collision, a spot the state has held for more than a decade, according to State Farm. The insurer tracks collisions with all animals, though deer are by far the most commonly struck. Nationally, the odds are 1 in 145. Here are the 10 states with the highest odds for July 2025 through June 2026:
- West Virginia: 1 in 46
- Montana: 1 in 54
- Wisconsin: 1 in 62
- Pennsylvania: 1 in 64
- Michigan: 1 in 68
- Iowa: 1 in 81
- Mississippi: 1 in 81
- Virginia: 1 in 81
- Maine: 1 in 85
- South Dakota: 1 in 86
Pennsylvania had the most estimated claims of any state, about 141,000.
Tips to avoid hitting a deer
To lower your odds of hitting a deer or other animal, State Farm and the Insurance Information Institute recommend:
- Slow down and stay alert, especially from dusk to dawn, when animals may be more active and harder to see.
- Use your high beams at night when there is no oncoming traffic. They light up the eyes of animals near the road.
- Take extra care in marked animal-crossing zones and where roads run between farm fields and woods.
- If an animal steps into your path, brake firmly and stay in your lane. Swerving can make you lose control or hit another vehicle.
- Don't rely on deer whistles, fences or reflectors. They haven't been proven to reduce collisions.
- Always wear your seat belt.
If you do hit one
Move your vehicle to a safe spot if you can and turn on your hazard lights, State Farm advises. Call police if the animal is blocking traffic, and stay away from an injured or frightened animal. Before driving on, check for leaking fluids, damaged tires and broken lights. Comprehensive coverage typically covers damage from animal collisions, subject to your policy's terms and deductible.
The crash in New Jersey still shapes how Gorchov drives. "I drive carefully, I'm on the lookout for deer," he said. He also drives a little slower, particularly at dusk and at night. Night, as he explained, is when many deer leave the forest for fields and gardens.
This story was produced by Campus Insights Media on behalf of Miami University, and reviewed and distributed by Stacker.
