Having had my most up-close encounters with deer and moose on Montana and Idaho "ranch" land, I stay wary. The deer haven't a clue what they're doing and are unpredictable while the moose do know and are willing to prove it. That said, they certainly aren't gunning for humans. If you're bicycling the roads of Yellowstone, you can have some even closer encounters with bison who are generally placid but can turn aggressive and are incredibly fast and agile. They think these nice paved paths were put there for their benefit. However, I'm still much more worried about mtn lions (OK, and skunks ).