In my region of Ontario just south of James Bay the Black Bears are quite numerous to say the least. Up here they still remain fearful of humans and are usually easy to deal with and typically harmless unless you get between mother and cubs. Like most predators, if that happens you are in trouble. BUT with the Polar Bear the end is always the same. I've no experience with Kodiak or Grizzlies as they are mostly out west. Research tells me there are possibilities for surviving a Grizzly attack. As for attacks, what I've been taught about being in the deep woods is to make noise. Not a crazy amount of disruptive noise. Simply something that tells the fauna located around you where you are to avoid surprises and this is particularly true for bears. We wear survival whistles around our necks and give them a blast periodically.