While collisions with cattle and wildlife are common -- about 3,000 a year in Colorado, according to the state highway department -- hitting a bison is rare. The bison's owner won't face any criminal penalties, particularly because the fences along the highway are maintained by the state, said a Colorado State Trooper.
Hitting a bison is not a minor incident - the animals stand about 6 feet tall and up to 2,000 pounds. According to the Rocky Mountain Buffalo Association, Colorado has about 50 bison ranches with between 5,000 and 10,000 head.
According to the National Highway Transportation Safety Administration, each year animal-vehicle collisions injure nearly 29,000 people, and cause more than 200 human fatalities and more than $1 billion in vehicle and other property damage.
In states such as Wyoming and Montana, where wild bison's' migratory routes are subdivided by roads and where grazing is common along open range, bison run-ins are more common. Over three days in Montana last year, 15 bison were killed by cars or trucks on a 10-mile stretch north of West Yellowstone. No humans were killed. Afterward, the Buffalo Field Campaign at Yellowstone National Park urged highway caution in a blog post.
Where open-range laws are in effect, ranchers don't have to fence in their livestock. If the neighbors want to keep cows off their land, they have to fence the beasts out. The principle dates back to the 1800s, when cattle barons let their herds roam over public land and any private land that wasn't fenced off.
Thirteen Western states, including Colorado, still have some kind of open-range law. Yet as the West becomes more populated, more people moving into rural neighborhoods are bothered by livestock straying onto their property, and increased traffic means more accidents involving livestock that stray onto roads.