Special situations require special measures; given your situation, a radio makes sense. I would imagine you would most likely be able to raise a response on a marine frequency on Isle Royale.<br><br>You ask about SAR in the NPS. It varies from park to park. Some parks are tiny; others are huge. Some are located in downtown areas and others are raw, screaming wilderness, where even the rangers disappear. Larger parks have their own SAR capability, but often coordinate with local SAR groups and the military for larger, more involved operations. I am biased, but I think in general, you are in pretty good hands for emergency situations when visiting a National Park Service area.<br><br>I am not familiar with the specifics of ranger operation on Isle Royale, but they have people at both Rock Harbor and Windigo(east and west ends). When I was last on the island (1983), a ranger patrolled from Amygdaloid Island, about the middle of the north shore. Obviously, while there will be a response, it probably won't be instantaneous, depending upon your location. Isle Royale is isolated enough that I doubt that there is quick response by helicopters, etc. in SAR situations, but I certainly don't know for sure. It might be worthwhile to email or call the Chief Ranger - he should be able to give you current information.