Nearly 3.5 million people visited Yellowstone National Park last year and two of them didn't make it out. They were killed, one partially eaten, by grizzly bears.

Now many are wondering what's going on, because from 1986 to 2010, there were no deadly encounters with grizzlies.

Jeff Hull set out to answer those questions in the June issue of Outside Magazine. What he found was a fairly simple answer: There are more people visiting Yellowstone, and because of a successful recovery program, there are also more bears.

The number of grizzlies in the Yellowstone region has jumped from 136 in 1975 to 602 in 2010. So human-bear encounters are no longer rare occurrences and people are not heeding warnings about what to do if they meet up with a grizzly in the wild.

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