An 83-year-old woman was gored by a bison at Yellowstone National Park : NPR

A herd of bison is seen in the Lamar Valley in Yellowstone National Park on August 3, 2016.

Matthew Brown/AP

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Matthew Brown/AP

An 83-year-old woman was seriously injured after being gored by a bison last weekend in Yellowstone National Park, the National Park Service said.

The bison was “defending its space” and came within a few meters of the woman on Saturday, the park said. This lifted her about a foot off the ground.

His current condition is unknown and the incident remains under investigation, the park said.

Bison are generally not aggressive, but can be aggressive when defending their territory. They kill humans more than any other animal in Yellowstone and can run three times faster than humans, the NPS said.

The National Park Service advises visitors to stay away from wild animals if they see them in places such as campsites, parking lots or trails. People should stay at least 25 yards from “bison, elk, bighorn sheep, deer, moose and coyotes” and at least 100 yards from wolves and bears.

Several people have been gored by bison in Yellowstone in recent years, and last year a tourist from Hawaii pleaded guilty to handling a bison calf, which ultimately led to its death.

The NPS said bison are overpopulated in the park. Many had to be hunted or captured and slaughtered, while others were relocated to Native American reservations and tribal lands.