Though many of the animals in the park are used to seeing humans, the wildlife is nonetheless wild and should not be fed or disturbed. Stay at least 100m away from bears and 25m from all other wild animals! Bison, elk, moose, bears, and nearly all large animals can attack! For any doubters, the National Park Service has put a series of animal attack videos online -- these animals are large, wild, and potentially dangerous, so give them their space. In addition, be aware that odors attract bears and other wildlife, so avoid carrying or cooking odorous foods and keep a clean camp; do not cook or store food in your tent. All food, garbage, or other odorous items used for preparing or cooking food must be secured from bears. Treat all odorous products such as soap, deodorant, or other toiletries in the same manner as food. Do not leave packs containing food unattended, even for a few minutes. Animals which obtain human food often become aggressive and dependent on human foods, and many can suffer ill health or death from eating a non-native diet.

When camping, either filter, boil, or otherwise purify drinking water. Waters may be polluted by animal and/or human wastes, and intestinal infections from drinking untreated water are increasingly common. Always stay on boardwalks in thermal areas. Scalding water underlies thin, breakable crusts; pools are near or above boiling temperatures. Every year visitors traveling off trail are seriously burned, and people have died from the scalding water. No swimming or bathing is allowed in thermal pools. The weather can change rapidly and with little warning. A sunny, warm day can quickly become a cold, rainy or even snowy experience. Hypothermia can be a concern. Be prepared for a variety of weather conditions by bringing along appropriate clothing. Lightning can and does injure and kill people in the park, so watch the sky and take shelter in a building if you hear thunder.