Every cougar kill I've seen the cat had ripped the belly and eaten the liver first. Some had also eaten a bit of the ham on the elk. Looked like that's always done at the time of the kill. Then they'll return to feed until the meat is no longer fresh.
Notice how the blood pooled on the ground by the neck wound. I figure the neck wound was made when the elk was killed otherwise if it had been done by a predator after the kill the blood would not have run like that.
Don't think that was a cat. Any other predator would have eaten much more of the kill and likely started around the hams.
Culprit is a two legged vermin.
