Record visitor numbers have created a sometimes dangerous frenzy, with selfie-taking tourists routinely breaking park rules and getting too close to Yellowstone's storied elk herds, grizzly bears, wolves and bison. Major parks are grappling with illegal camping, vandalism, theft of resources, wildlife harassment and other visitor misbehavior. In July alone, law enforcement rangers handled more than 11,000 incidents at the 10 most visited national parks.
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