Widely dispersed throughout Yellowstone National Park during the summer, mule deer migrate seasonally and most of the population winters outside of the park. The Greater Yellowstone Ecosystem is home to both mule deer and white-tailed deer.

Yellowstone National Park is home to two primary species of deer: Mule Deer and White-tailed Deer, though they are often overshadowed by their larger cousins, the elk and moose. Mule deer are the most common and are easily identified by their large, "mule-like" ears and their distinctive "stotting" gait, where they jump with all four feet hitting the ground at once. You will frequently see them in the northern range, particularly around Mammoth Hot Springs and the Tower-Roosevelt area, where they forage in the brush and meadows. White-tailed deer are less common and tend to stay in the dense forests and riparian areas along the rivers in the park's lower elevations. While they are smaller than the park's iconic megafauna, they play a vital role in the ecosystem as a food source for predators like wolves, mountain lions, and grizzly bears. In 2026, wildlife biologists monitor these populations closely, especially as "Chronic Wasting Disease" remains a concern in the region. For visitors, deer sightings are a daily occurrence, but they require a sharper eye than a massive herd of bison; they are most active during the "crepuscular" hours of dawn and dusk.