Recent events at Yellowstone grabbed national headlines:
Yellowstone boasts the most large, dangerous carnivores among those parks, but each has its risks. In Rocky Mountain National Park, it's elk that become more aggressive during mating season. In Yosemite, it's towering waterfalls where visitors insist on swimming near the edge. In the Grand Canyon, it's squirrels habituated to humans and sometimes quick to bite an outstretched hand.
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.