The coyotes know exactly* where the invisible fence begins and ends, without the benefit of ever wearing a shock collar. How do I know? Because they intentionally leave their scat on their side of the invisible fence, creating a demilitarized zone as precise and as well-observed as anything on the Korean peninsula.*

Hmm.. couldn't this be just a result of the dogs not having marked the territory where the invisible fence is? As in, it's just territory essentially open for the taking?