Use extra caution this time of year - the bison rut is beginning! You may see mature male bison with their mouths open, tongues out, and upper lips pulled back. This is how bull bison sniff pheromones and determine whether a female is ready to breed. Bulls will also display their dominance by bellowing, wallowing, and engaging in fights with other bulls. The winners earn the right to mate with receptive females. Bison are wild and unpredictable, no matter how docile they may appear to be. Be sure to always maintain a distance of at least 25 yards (23 meters) from them, and if a bison charges, retreat! 👉 Learn more about our safety tips at: go.nps.gov/YELLsafety