Most Americans know about the geothermal extravaganza called Mammoth Hot Springs, nestled in a spectacular landscape in Yellowstone National Park. It is also a place that must serve visitors as they enjoy this exceptional place and its amazing sights: A male bison weighing well over half a ton, with a toss of his head and a stutter step, shoos away a contingent of Asian tourists as they naively crowd his space. Or elk stepping between cars in a never-ending flow of vehicles and stopping traffic cold, or else pooping on the sidewalks, resting in the shade of the post office, or more dramatically, a large male elk in full rutting regalia, taking out the grill on a Jeep after its driver treats the animal with contempt. This may provide riveting entertainment, but it also reveals that this historical site is threatening to burst both its human and ecological seams.