Oh deer! Expect to see more during the cooler season
When you’re out on the roads this evening, count the cars. One of every 63 Pennsylvania drivers that you pass is likely to collide with a deer this year.
An annual study conducted by State Farm insurance ranks Pennsylvania third highest for deer collisions, with a 6.3 percent higher chance this year than in 2016. The 15-year study determines the odds and ranks states by the potential risk of a collision with a deer, elk, moose or caribou.
West Virginia continues to lead the nation in insurance claims involving deer. Montana ranks No. 2 on the list.
Whether a vehicle strikes a deer or a running deer collides with a moving vehicle, a deer strike can cause serious damage, human injury and sometimes death if the animal rolls through the windshield. Many deer die instantly, but some survive in a disfigured state that complicates the rest of their lives.
Most experienced Pennsylvania drivers know that deer are generally active between dusk and dawn, and that the threat of collision is greatest in fall and winter. Some drivers believe the presence of hunters in the autumn woods pushes deer onto the roads, but State Farm attributes the increased deer activity to simple biology.
“The main reason they’re roaming around is they’re mating,” said State Farm spokeswoman Missy Dundov. “The months we see the most deer collisions are October, November and December. They’re on the move more. This is their mating season. It more than doubles the likelihood that drivers will have deer-vehicle collisions.”
Female white-tailed deer are fertile for only one 24-hour period per year. At Pennsylvania’s latitude, that day of estrus occurs at some point from October through December, a mating time commonly called the rut. The breeding season can be extended when adult does that do not become pregnant re-enter estrus about 22 days later.
“Photoperiod, or day length, triggers physiological changes in deer that prompt breeding,” said Jeannine Fleegle, a deer biologist with the state Game Commission. “Simply put, [it’s when the] females ovulate, allowing them to become pregnant. ... This is the result of hormonal changes which are triggered by the shortening days of the fall.”
At this time, does produce pheromone scents that signal to bucks that they’re fertile and willing to mate. White-tailed deer are not monogamous, and a doe may couple with several bucks.
“Males go into search mode while females sit and wait,” Ms. Fleegle said.
In the male version of the rut, bucks produce high levels of testosterone, triggering semen production and glandular secretions. Bucks become fiercelycompetitive over breeding rights. They often fight among themselves and attack anything — occasionally even a human — that appears to hinder access to a female.
Mature bucks in their prime may mate with many does, while young adults and older males may not have the chance to mate during a rutting period.
“I’m not sure [the rut] impacts their thinking per se, but it does impact behavior,” said Ms. Fleegle. “The ultimate goal of any [organism] is to pass on his or her genes. Deer get a short window each year in
which to do this. So that is where all their efforts are directed. ... Everything else is secondary.”
In the heat of the rut, several bucks at a time may chase a single doe, whether or not she’s actually in estrus. Serious injuries can occur during combat for mating rights. Sometimes antlers become irrevocably entangled, and both of the deer may die. Rut-induced obsession is the reason a wily 10-point buck that creeps past an archer in September may run blindly onto a busy highway in November. In fact, hunting seasons are set to coincide with the times when deer are most careless.
In autumn and early winter, Pennsylvania drivers should expect deer to behave irrationally. In urban areas with no deer population control, be prepared for more deer on the roads than usual. And those yellow roadway “deer crossing” signs? They warn of routine deer travel routes, not the wild nose-to-theground, full-speed gallops that occur randomly during the rut.