It is funny, but around here mountain lions are almost exclusively predators on deer. There apparently is a window of a few months when two year old males get kicked out of mom's den/pack, when they have to carve out their own hunting territory somewhere and some of them do eat other animals, but talking to my large scale ranching neighbors, nobody has been able to recall losing a calf to a mountain lion. We have two dens pretty close to here (less than a mile), and we haven't ever lost a calf to a mountain lion, or coyote for that matter.
Around here, I would love to see grizzly bears reintroduced as the feral pigs have no apex predator, and grizzly apparently used to hunt them. The elk that have been reintroduced locally are like smoke, and vanish about as soon as they sense humans. We have seen them occasionally, but I have neighbors that have never seen one in their lifetimes. A neighboring ranch had some running with their Herefords, and thought that they would do the elk a favor, and moved the cows to a different area of the ranch. The elk got spooked by the lack of cattle, and left. Last that I heard it has been more than twenty years and they still haven't returned. My takeaway is that wildlife management isn't simple...
All the best,
Peter