Originally Posted by dopey
My guess is mature cougar vs. very young, very old or sick bear. It is hard to imagine that even the hungriest mountain lion would choose a healthy bear as its prey. That would be a very very low risk and effort v. reward ratio.
Your surmise would seem to be most reasonable, but apparently such was not necessarily the case. Rather than the lion seeing the grizzly as prey, perhaps it was more of a "turf war" between top end predators, much as wolfpacks will kill mountain lions on occasion without eating them. Here is some interesting material from Storer and Tevis' classic California Grizzly:
"Three California accounts detail something of the antagonism between the grizzly and the mountain lion, or panther. Livingstone Stone was told by the McCloud River Indians that the panther always killed the grizzly when the two fought. They said that the grizzly was afraid of the lion and that the latter would spring on the bear's shoulders and cut its throat. Stone saw place in the mountains where the ground had been torn up, evidence of a desperate conflict between a panther and a bear. The Indians said they had found bears killed by panthers but no panther a bear had killed. "An actual bear-and-panther in the central coast region was watched in the 1840's. Three hunters, originally seeking a female grizzly with cubs, had been grounded by the escape of their horses. Going cautiously along a creek bordered by willows and grapevines, they approached a waterfall that plunged into a green, transparent pool over which a large tree had fallen. "With the sounds of the torrent came...the growls of two wild beasts, alternate and furious. "On the right hand, squatted on one end of the bridge, was a small male grizzly, and opposed to him, on the other end, a full grown panther, who was tearing up the bark of the trunk and gathering and relaxing herself as if for a spring. The alternate roaring of these infuriated beasts filled the valley with horrible echoes. "We watched them a minute or more. The bear was wounded, a large flap of flesh torn over its left eye and the blood dripping in the pool. My companion bade me shoot the tiger, while he took charge of the bear. We fired at the same instant; but, instead of falling, these two forest warriors rushed together at the centre of the bridge, the bear rising and opening to receive the tiger, who fixed her mighty jaws in the throat of her antagonist and began kicking at his bowels with the force of an engine. At the instant, both rolled over, plunged and disappeared. We could see them stuggling in the depths of the pool; bubbles of air rose to the surface, and the water became dark with gore. It may have been five minutes or more before they floated up dead, and their bodies rolled slowly down the stream.
"Another natural fight between a grizzly and a mountain lion was described in the San Bernardino Argus
of 1873: "Some hunters were witness to a desperate fight in the San Jacinto Mountains, the other day, between a mountain lion and a bear. The fight is described as terrific. The superior strength of the bear easily enabled him to throw his antagonist down, but the latter used his paws and jaws so fearfully that the bear could not keep him under. Both animals were covered with blood. They fought till both were exhausted, when the lion dragged himself off into the jungle, leaving the bruno in possession of the field."
(pp.71-3) Here's another passage (p. 151): "According to Frank Post of Big Sur, mountain lions were sometimes taken in the live traps built near Monterey to catch bears for the arena. Then a bear-and-lion fight would be arranged. Mr. Post saw such a contest at Castroville in 1865 when he was six years old and remembered it vividly. The lion, which seemed to have no fear, leaped onto the bear's back and while clinging there and facing forward scratched the grizzly's eyes and nose with its claws. The bear repeatedly rolled over onto the ground to rid himself of his adversary; but as soon as the bear was upright, the cat would leap onto his back again. This agility finally decided the struggle in favor of the lion. [Early California settler and sometime Los Angeles Ranger Horace] "Bell mentioned a fight staged in Mexico between a grizzly and a lion that had been imported from Africa: "When, a few years ago, a Los Angeles County grizzly was sent to Monterrey, Mexico to be pitted against the man-killing African lion "Parnell," the great Californian handled the African king as a cat would a rat. He killed him so quickly that the big audience hardly knew how it was done."
Evidently the superior speed and agility of the mountain lion make it a more formidable antagonist for the grizzly than the mighty African lion!