Grizzly bears are capable of running as fast as 40 mph. Close encounters with hikers are a risk in the Yellowstone National Park area in Wyoming, Montana and Idaho, and park rangers recommend packing protection akin to mace for Manhattan muggers — bear spray. The grizzly population of the Greater Yellowstone Ecosystem has more than tripled since 1987. About 150 call the park home. The bears were declared a "threatened species" in the lower 48 states in 1975. Grizzly relatives also reside in Alaska. Non-lethal bear spray — carried in a cartridge resembling a small fire extinguisher — expels "a...