The discovery of two tagged wolves killed by mountain lions has researchers scratching their heads.

This year, researchers in the Bitterroot Valley in Montana have discovered the carcasses of two radio-collared wolves, both apparently killed by mountain lions.

One was discovered in January with puncture wounds characteristic of a mountain lion attack. In that case, a deer carcass was found nearby, implying the two carnivores may have fought it out.

Earlier this week, another collared wolf was discovered dead with the same wounds — but this time there was no sign of competition.

“It’s hard to say what happened,” said Liz Bradley, a state wolf specialist with Montana Fish, Wildlife & Parks. “There was no elk or deer carcass nearby that they may have been competing over.”

Bradley said two wolves were also discovered in 2011 with similar cougar wounds, leaving only four packs in Montana with a collared wolf, down three from the end of 2011. Bradley estimates there are about 14 packs in Bitterroot Valley.