POCATELLO, Idaho (AP) -- Two men accused of killing a grizzly bear cub near Island Park three years ago pleaded not guilty on Tuesday, the U.S. Department of Justice said.

Tim L. Brown of Island Park and Brad Hoopes of St. Anthony are scheduled to stand trial on the misdemeanor charge in U.S. District Court in Pocatello on Dec. 5, said Jean McNeil, a spokeswoman for the U.S. attorney's office.

In a separate case, Dan Walters, a bow hunter from Kentucky, has been ordered to pay $15,000 in restitution for killing the grizzly cub's mother. Walters, who pleaded guilty to the misdemeanor in January, also had his hunting privileges revoked for two years.

Grizzly bears are threatened species under the Endangered Species Act, making it illegal to kill the animals.

Scott Bragonier, a special agent with the U.S. Fish and Wildlife Service, said Walters told investigators that he was hunting alone when he spotted the adult female grizzly and the yearling cub and mistook them for black bears. Walters shot the adult animal with his bow and arrow, and then tracked it until evening.

The next day, Bragonier said, Walters allegedly returned with Brown, Hoopes and another man and the four discovered the adult grizzly, dead from the arrow wound.

''It was at that time that they positively identified the bears as being grizzly bears,'' Bragonier said.

Hoopes and Brown allegedly destroyed the adult grizzly's radio collar and tracked the cub, a yearling female, and killed it as well, Bragonier said.

Other archery hunters in the area found the dead bears, he said, and notified authorities. Even without its mother, the cub was old enough to have survived on its own, he said.

It was also old enough to attack and cause harm, said Lynn Hossner, the St. Anthony attorney representing Brown. The animal was near the corpse of the older grizzly and threatened the two when they unwittingly approached, he said, forcing them to shoot the beast in self-defense.

''The cub attacked Brown and Hoopes. They were lucky they were able to protect themselves,'' Hossner said.

Neither of the men was wounded in the attack, he said.

David Maguire, the attorney representing Hoopes, said he had just been assigned to the case and was not yet familiar enough with the details to comment.

The two bears traveled regularly between Yellowstone National Park and the Sawtelle Peak area in Idaho, McNeil said, and neither had been involved in any human encounters.

There are just under 600 grizzly bears in the greater Yellowstone ecosystem according to last year's estimate, said Mark Haroldson with the U.S. Geological Survey Interagency Grizzly Bear Study Team. ''

''We're fairly certain the population has been increasing and expanding its range over the last decade or so,'' Haroldson said.

Officials said the grizzly deaths were a setback for the population, which has few reproductive females.