Thermal Areas
Yellowstone’s thermal features are extraordinary natural wonders. Most are formed through decades or centuries of natural processes. It is illegal to throw objects into features, deface them or remove any natural features from the park. Stay on boardwalks and designated trails; watch for frosty and icy trails and boardwalks, especially in the morning. Pets are prohibited in thermal areas. Swimming or bathing in the thermal pools or streams whose waters flow entirely from a thermal spring or pool is prohibited.
Wildlife
Yellowstone National Park has the largest concentration of free-roaming wildlife in the lower 48 states and the global temperate zone. All wildlife, especially bison and bears are unpredictable and dangerous. Keep a safe distance from all wildlife; view from your car. It is against the law to approach within 100 yards of bears or within 25 yards of other wildlife. For your safety and the animals welfare, avoid wildlife with young. Visit the Viewing Wildlife page for more information.
Bears
All of Yellowstone is bear country. Bears may appear tolerant of people but are known to attack without warning. Do not approach bears! Feeding wildlife is unlawful. Never leave food or garbage unattended. To decrease the likelihood of personal injury, store all food and cooking utensils in a secure place. Backcountry use may be restricted in some areas to reduce human related impacts on bears in high density grizzly bear habitat. You can learn how to minimize the dangers associated with a bear encounter.
Park Features
Leave natural, historical, and archeological items in place. Collecting natural or archeological objects, or removing, defacing or destroying any plant, animal, or mineral is prohibited.
Cyclists / Pedestrians
Bicycling is permitted on established public roads and designated routes. There are no bicycle paths along roadways. Park roads are narrow and winding; most do not have a shoulder, or shoulders are covered with gravel. Vehicles, especially motor homes or those towing trailers, may have wide mirrors, posing an additional hazard for cyclists and pedestrians. All bikes are prohibited on backcountry trails and boardwalks. Motorhomes and towing units are required to remove detachable side mirrors when not pulling trailers.
Swimming
There are no swimming pools in Yellowstone, and swimming, bathing, or wading in thermal features, or in streams whose waters flow from thermal features, is illegal. River, stream, and lake water is so cold that hypothermia is a serious possibility. Swimming is generally discouraged.