A teenager working at a Colorado camp woke up to the sound of "crunching" - only to find out it was a black bear biting his head.

The 19-year-old woke up at around 4 am to discover his head was inside the mouth of the bear, which was trying to pull him out of his sleeping bag as he slept outside at Glacier View Ranch 48 miles northwest of Denver, Colorado Parks and Wildlife spokeswoman Jennifer Churchill said.

The teen punched and hit it and other staffers who were sleeping nearby yelled and swatted at the bear, which eventually left, she said.

The staffer, identified only as Dylan, was treated briefly at a hospital and released.