Originally Posted by DreadMagus
No - they move when they see "or" hear something that triggers their "interest". That is established setting lore. And they keep moving until something stops them or distracts them.
That's how you end up with herds that follow trains for miles and miles and miles... even when they can't see or hear said train anymore.
End of the day, it's irrelevant. They're either stupid enough to chase the next lightning bolt or be lead off intentionally. Again, not a difficult concept.
Being able to get corn from a cornfield is a pretty safe bet. That shouldn't require explanation. Everything else, that's a fact. That farming's one of the oldest human technologies? Fact. Seriously, why do you think the region around the fertile crescent is known as the cradle of civilization? That information on how to farm is recorded in things like books? No, that's a fact too.
The bigger assumption that you're going to find lootable resources like non-perishable foods elsewhere.