Yellowstone's bison herd, totaling close to 5,000, enjoy free range over the park. Occasionally this creates some problems as the buffalo are apt to roam. Park rangers must capture strays as they leave the park for fear of spreading brucellosis to surrounding ranches.
Although the bison is wild, they seem well adjusted to park visitors and automobiles. Traffic jams, where wild animals are spotted, are commonplace along the park's routes. Spotting Yellowstone's wild animals always creates a stir of excitement.