Yellowstone Bison Attacks Spike in July as Mating Season Triggers Aggression

Yellowstone National Park has recorded multiple bison attacks in July 2026, including an incident on July 20 when a bull gored a tourist’s tire in traffic and an earlier attack that threw a 65-year-old man eight feet into the air. With roughly 5,000 bison in the park and mating season underway, biologists warn that bulls are unusually aggressive and visitors are ignoring the mandatory 25-yard distance rule.

Three attacks in one month

On July 20, a bull bison charged through bumper-to-bumper traffic in Hayden Valley and punctured a vehicle’s front tire with its horn, according to video captured by visitor Tonya Names. Earlier that month, on July 10, a 65-year-old man was tossed eight feet in the air by a bison. In June, a 12-year-old was injured near Mud Volcano and hospitalized. All three incidents occurred when visitors were too close to the animals.

Mating season amplifies territorial behavior

The bison rut runs from mid-July through September, a period when mature bulls compete for mates and defend their space far more aggressively than usual. George Wuerthner, a biologist who has worked in the Greater Yellowstone Ecosystem for decades and is president of the Montana Wild Bison Coalition, explained that bulls become “all ginned up on hormones” during this window. Hayden Valley, where the July 20 attack occurred, is a central park location where large numbers of bison congregate as mating season begins.

Visitors ignore the 25-yard rule

Yellowstone and Glacier National Parks require visitors to stay at least 25 yards away from bison. Ken Klemm, past president of the National Bison Association and manager of some of the world’s largest bison ranches, told Cowboy State Daily that the problem is not bison behavior but human behavior. “This isn’t a bug, it’s a feature of bison living in close quarters with people and not being trained to be wary of them,” Klemm said. The July 20 tire incident occurred when a driver moved forward too quickly, prompting the bull to react defensively.

Bear spray and distance are the best defenses

Wuerthner said keeping a safe distance from bison is the best way to avoid conflict. If confrontation becomes unavoidable, bear spray works as a bison deterrent, though Klemm cautioned that it requires training. “You have to get both eyes and the nose. If you get them in both eyes and the nose, they know to stop,” Klemm said. “However, just carrying bear spray with no training or experience is ill-advised.” He added that users must be mindful of wind direction.

Final Thoughts

Yellowstone visitors face real danger during bison mating season. The park’s 5,000 bison are behaving normally, but tourists who ignore the 25-yard rule and approach too closely are triggering defensive attacks. Maintaining distance and understanding that bulls are territorial from July through September is essential.

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