Yes, that would be pretty cool. Wouldn't want it to happen all the time though, cause you'd want there to be some leftovers for the players too .
That's why there would be herds, and there would be roaming predators, and then some predators that live in lionic prides, and they would swarm you, but you were super-human PC character and can kill them all!
But seriously, an actual ecology in an MMO would be AWESOME.