The national parks may be getting older, but their visitors do not appear to be getting any wiser.

As the National Park Service celebrates its 100th anniversary, parks around the country are struggling with how to curb vandalism, theft of resources, and other risky, rule-breaking behaviors. Law enforcement records suggest problems are on the rise at Yellowstone National Park and others, including the Grand Canyon and the Great Smoky Mountains.

The rise in bad behavior comes at a time when the national parks are more popular than ever. But that popularity has led some to worry that the parks system isn't adequately equipped to deal with an influx of visitors. As Todd Wilkinson reported for The Christian Science Monitor last month:

Last year, Yellowstone hit more than 4 million visits for the first time in history. It is poised to significantly surpass those numbers in 2016, the centennial year of the National Park Service. But behind all those cars and tour buses in the land of lodgepole pine looms a fundamental question: Is such soaring popularity good or bad for Yellowstone – and, more broadly, for the national park system as a whole? Can America’s outdoor crown jewels survive unmarred for another 100 years? .... Critics say the Park Service – beleaguered by deteriorating roads and buildings, threats to natural resources, overwhelming public use, and the potential effects of climate change – is ill-equipped to steward its 411 parks, cultural sites, and historical monuments forward another 100 years. They believe the sacred national park experience that so many people journey to see has already vanished at some of the most popular destinations and will only get worse without a serious infusion of money and a rededication to preservation.

One of the most common offenses, officials say, is getting too close to animals, oftentimes in pursuit of the perfect photo. This can have disastrous consequences, as illustrated by a woman who was charged by an elk at Jackson Hole in June after ignoring the instructions of her nature guide and a 16-year-old girl from Taiwan who was gored by a bison at Yellowstone last year while posing for a group photo.

Jody Tibbitts, the nature guide accompanying the woman who was charged by an elk, told CNN that he had noticed a change in the way park visitors interact with wildlife in recent years.

"Prior to having high definition cameras in our pockets, people seemed more courteous to animals," said Mr. Tibbitts, who has been a tour guide for 25 years. "It seems like people are being more brave and taking more chances and not thinking about the consequences."

Even rule violations rooted in good intentions can have harmful consequences. In May, visitors became concerned that a newborn bison calf might be cold, so they put it in their car to bring to park officials. When the officials tried to reunite the calf with its herd, it was rejected and had to be euthanized.

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To prevent visitors from breaking the rules, either by approaching wildlife or walking on a hot spring, Yellowstone is making an effort to ensure that all visitors are aware of the rules by posting additional signs and printing pamphlets in different languages, Yellowstone superintendent Dan Wenk told NPR.

"The difficulty is, is that our visitation changes every two to three days," Mr. Wenk explained.