culling the herd

     Lions don't cull herds--of anything.  Lions, when hungry, pounce on the creature that looks easiest to catch. If the lion catches the creature, it eats it. No animal "culls" herds--or works with the idea of enforcing the notion of "survival of the fittest". People may do this, if they keep herds of cattle, for instance. Perhaps they kill all of the weakest to have for dinner, and are left with the stronger animals to reproduce and increase the herd. This would be "culling " a herd, as beans are culled by removing the "bad" ones, or clumps of dirt that may be mixed in with them.  Lions and other predators do not do this, so to continue to state that they do is poor science and worse grammar.