The Alaska Dispatch News reports the female brown bear was defending her cubs when it mauled the Alaska Army National Guard soldier Sunday morning at Joint Base Elmendorf-Richardson.
The soldier's name hasn't been released. The soldier was listed in stable condition Sunday afternoon.
Base officials say the soldier was participating in a navigation exercise that involves giving soldiers compasses and maps and timing them as they make their way alone to locations on the course.
Sunday's attack was the second mauling at the base in about two months.
Jessica Gamboa, a soldier's wife, was badly mauled May 18 as she jogged on a trail.