Yellowstone National Park officials have closed an area in the northwestern corner of the park to off-trail travel to protect a litter of wolf pups that was abandoned last month.

No off-trail travel along the Daly Creek Trail will be allowed through Sept. 21, but visitors still will be allowed to hike on the trail.

The pups were abandoned by their mother after she was injured Aug. 12. Park officials said the adult wolf was possibly struck by a vehicle and was last spotted near the park’s northern border on Wednesday.

The pups have been frequenting the area near U.S. Highway 191 and appear in poor physical condition, officials said. Biologists have been trying to keep the young wolves away from the road and are providing them with supplemental food.

Two other adult wolves have remained in the area, and biologists said they hoped they would begin caring for the pups.