Nothing kills more fawns/calves on the ground than a bear does. Bears that learned this behavior with territory in a calving ground or fawning areas have a single minded focus to find the calves and are very successful at it.
Coyotes do this as well, but also get chased off.
Wolves will go for the wet cows and run the whole freaking herd out of the calving grounds leaving all the calves to be half starved bear food. When a calf gets up out of it's hidey hole driven by hunger and calling for momma....well it don't live long.
cougar take a *lot* of yearlings