re: Variations in Human Intelligence vs Animal Intelligence

I would expect with herding animals, such as zebras, variations from average would be detrimental to an individual. Instinctive behaviors, such as favoring being in the middle of a herd, would likely be beneficial.

With omnivores and carnivores, often pack animals, higher intelligence would make hunting more effective.

I've had dogs who would stalk a squirrel, and when it ran for the tree, the dog learned to cut the angle, anticipating where the squirrel would end up. Other dogs always simply chased directly behind, never figuring out another strategy.

Observing and anticipating behaviors and adjusting techniques for success is a fairly simple metric for intelligence in animals.