YELLOWSTONE NATIONAL PARK, Wyo. — Tourist John Gleason crept through the grass, four small children close behind, inching toward a bull elk with antlers like small trees at the edge of a meadow in Yellowstone National Park.

“They’re going to give me a heart attack,” said Gleason’s mother-in-law, Barbara Henry, as the group came within about a dozen yards of the massive animal.

The elk’s ears then pricked up, and it eyed the children and Washington state man before leaping up a hillside. Other tourists – likewise ignoring rules to keep 25 yards from wildlife – picked up the pursuit, snapping pictures as they pressed forward and forced the animal into headlong retreat.

Record visitor numbers at the nation’s first national park have transformed its annual summer rush into 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.

Law enforcement records obtained by the Associated Press suggest such problems are on the rise at the park, offering a stark illustration of the pressures facing some of America’s most treasured lands as the National Park Service marks its 100th anniversary.

From Tennessee’s Great Smoky Mountains to the Grand Canyon of Arizona, major parks are grappling with illegal camping, vandalism, theft of resources, wildlife harassment and other visitor misbehavior, according to the records obtained through a Freedom of Information Act request.

In July alone, law enforcement rangers handled more than 11,000 incidents at the 10 most visited national parks.

Often the incidents go unaddressed, such as when Gleason and the children approached the bull elk with no park personnel around. Gleason said he was “maybe” too close but felt comfortable in the situation as an experienced hunter who’s spent lots of time outdoors.

These transgressions add to rangers’ growing workload.

“It’s more like going to a carnival. If you look at the cumulative impacts, the trends are not good,” said Susan Clark, a Yale University professor of wildlife ecology who has been conducting research in the Yellowstone area for 48 years. “The basic question is, ‘What is the appropriate relationship with humans and nature?’ We as a society have not been clear about what that ought to be, and so it’s really, really messy and nasty.”

The flouting of park rules stems from disbelief among visitors that they will get hurt, said Yellowstone Superintendent Dan Wenk. “I can’t tell you how many times I have to talk to people and say, ‘Step back. There’s a dangerous animal,’ and they look at me like I have three heads,” he said.Wenk said the rise in popularity of social media complicates keeping visitors safe.

“You take a picture of yourself standing 10 feet in front of a bison, and all of a sudden a few hundred people see it, and it’s reposted – at the same time we’re telling everybody wildlife is dangerous,” Wenk said. “They get incongruous messages and then it happens. They get too close, and the bison charges.”