Heads Up, Illinois Drivers: Deer Mating Season Is Here Once Again

Every autumn in Northern Illinois, the deer population of Illinois begins the mating season of the white‑tailed deer. Deer mating season, also known as the “rut,” sees male deer (bucks) and female deer (does) engaging in heightened activity, behavior changes, and movements that can really wreck a day (and a vehicle) for motorists.

If we only had a few deer in Illinois, mating season wouldn't be nearly as dangerous as it is, but Illinois' population of white-tailed deer is doing nothing but getting larger each year.

According to DeerFriendly.com, Illinois has right around 730,000 white-tailed deer living within our borders (according to 2024 estimates), which is an increase over 2023 (690,000) and an even bigger increase over 2019 (670,000).

Welcome To The 2025 Rut In Northern Illinois

In Illinois, the rut begins around October and can extend through January, with the activity peak usually in mid‑November, but that can change based upon different weather conditions.

Here's a timeline breakdown of deer mating season here in Illinois:

• In late August to September the bucks transition into the “hard antler” phase, which is the shedding of the velvet on their antlers, increasing testosterone levels, and marking their territory.
• From mid‑October through late October the “seeking” phase begins, with bucks actively searching for does that are eligible for mating.
• The “chasing” phase, usually in late October into early November, sees bucks following does, sometimes very closely, in active pursuit. White-tailed deer movement and activity increases dramatically, which makes the roads more dangerous.
• The peak rut (usually around November 10th–20th) may involve bucks locking onto a receptive doe for days, breeding, defending her from other males, and then sticking around in one general area. Both sexes are less focused on feeding or being alert.
• There may be more of this activity later. A second rut cycle sometimes happens in early to mid‑December for the small percentage of females that didn’t breed earlier.

The Illinois Department Of Transportation (IDOT) Says That Deer Become Very Mobile During The Rut, Which Means Higher Danger On The Road, Especially At Dawn And Dusk

If you've lived around here for a while, you know that fall driving requires some extra vigilance to make sure you don't have a bad encounter when you least expect it.

Some of Illinois' numbers when it comes to deer driving dangers (hat tip to Patch.com):

• In 2024, there were 14,436 crashes involving deer in Illinois. Of those, 13,733 resulted in vehicle or property damage, 698 caused injuries, and 5 resulted in fatalities.
• Of all the crashes, 42 % occurred in October, November or December, with 21 % happening in November alone.
• Nearly 70 percent of the crashes took place in rural areas, but the single county with the most collisions was Cook County.
• 79 % happened during twilight or at night.

Obviously we need to make sure we're alert during this time of year here in Illinois, and we're not even the most dangerous state when it comes to vehicle-deer accidents. That title goes to West Virginia, where drivers there have about a 1-in-40 chance of an encounter.

The 5 states with the highest risk of an animal (mostly deer) collision per driver are West Virginia's 1-in-40, followed by Montana (1-in-54), Michigan (1-in-59), Pennsylvania (1-in-61), and Wisconsin (1-in-63).