Approximately 25 dead cows were found in the Yampa River at Dinosaur National Monument last week.
Dave Panebaker, chief ranger at the monument, said monument officials first received a report about the cattle on April 1 from rafters.
"We're not sure how they died," he said. "They were bloated and in the river at different locations for about 10 miles."
Panebaker said there is a chance the cattle walked out on the ice, fell through, and drowned
The discoveries were made between mile marker 10 and mile marker 18 in the Yampa River.
Panebaker said the owner or owners of the cattle has not been determined. The chief ranger said the Mantle family, which has grazing permits in the area, had been contacted.
"We contacted the Mantles and gave them a description of the cattle but have not heard anything back yet," he said.
Lonnie Mantle said he did not think the cows belonged to his family.
"To the best of my knowledge none of them are ours," he said. "All of ours are accounted for. They called and gave us a description but I don't get excited about going and looking at a bunch of dead cows."
Mantle said there are probably 100 ranchers up and down the river who could have lost those cows.
He said it is not uncommon for cattle to walk out on the ice and fall through.
"Especially during a winter like this where you have a few days of cold weather then a few days of warm weather," Mantle said. "In years past I've lost a horse or two in there."
The fact that such a large number were discovered did not alarm Mantle either.
"I've seen 50 animals of different kinds go by on the high water before," he said.
Panebaker said no decisions have been made on what to do with the dead cows.
"We've let the river runners know there are dead cows in that section," he said.
"Because they're so bloated it makes them more difficult to get out."
Panebaker said he has contacted the Environmental Protection Agency and the Visiting Nurse Association in Craig to determine if there might be a health hazard.
"Right now we're basically monitoring the situation," he said. "We're trying to find out if there's a health risk."
Panebaker said he could not estimate how long the cows had been there.
"Some seemed to be further along in decaying than others but that could have been because they were farther in the water," he said. "I didn't see where it looked like they had been shot or anything like that. We're not sure what happened."