There is a world somewhere between reality and fiction. Although ignored by many, it is very real and so are those living in it. This forum is about the natural world. Here, wild animals will be heard and respected. The forum offers a glimpse into an unknown world as well as a room with a view on the present and the future. Anyone able to speak on behalf of those living in the emerald forest and the deep blue sea is invited to join.
Grizzlies and polar bears do indeed carry more fat than the other bear species; this is true. However, that extra muscle - the shoulder hump - is very real. As for tigers and bears, the tiger most aggressive towards bears is the Amur tiger. He hunts both grizzlies and Asiatic black bears. You will read from many sources that tigers hunt and kill more brown bears than black bears, but DNA testing of tiger-dung proves them wrong. This was an assumption due to the black bear's tree-climbing ability.
Also note; having predators does not cause great physical strength. That mostly comes from food-finding methods and in male-to-male competition for mating rights.