Source Unknown:

     If you are considering doing some camping this summer, please note the
     following public service announcement:
     In Alaska, tourists are warned to wear tiny bells on their clothing
     when hiking in bear country. The bells warn away MOST bears (brown,
black,
     etc.), but be careful because they do not scare Grizzly Bears.

     Tourists are cautioned to watch the ground on the trail, paying
     particular attention to bear droppings to be alert for the presence
     of Grizzly Bears. One can easily spot a Grizzly dropping because it
     has tiny bells in it.