FF, sort of a half-educated guess from what folks have said about mountain lion behavior and needs. Sort of a "so many pounds per day, average; there are just so many animals per unit area as prey, etc., etc."
The wildlife biologists guesstimate that it takes in the neighborhood of some 25 square miles of this Chihuahuan Desert to support a pair of mountain lions. Well, that sure varies, given how many there actually are around here on an occasional basis. But, long term average, it seems pretty reasonable.
It's a bit difficult to be really accurate in this sort of thing when predators are as highly mobile as cougars or wolves. If they deplete the food supply, they move on. The exit means a recovery of prey species; predators return.
There is more "seems like" than there is numerical exactitude.