When I was trekking in the Canadian Rockies a few years back I came across a notice which read something along the following lines :-
"As this is the bear season hikers are advised that it is a good idea to announce your presence by talking to your companions, wearing bright clothes, or wearing little bells on your boots. It is also good practice to carry a can of pepper spray.
It is also useful to be able to identify bears by their droppings. Black bear droppings are small and round, contain clusters of seeds and nuts, and smell of ammonia. On the other hand, grizzly bear droppings are larger and longer, and contain little bells and smell of pepper."