The park is home to more than 30 mammal species. Some of these, however, such as the American mink ( Mustela vison ) and the short-tailed shrew ( Blarina brevicauda ) are not frequently observed. Hiking the Appalachian Trail up Loudoun Heights, gray and fox squirrels ( Sciurus carolinensis and S. niger ) can be viewed scurrying to stash their food, while eastern chipmunks ( Tamias striatus ) are commonly seen running right along the trail's edge. In a 2001 mammal survey, the southern flying squirrel ( Glaucomys volans ) was found to be making its home within the park.
During the early morning hours, white-tailed deer ( Odocoileus virginianus ) can be found browsing on understory vegetation as hikers make their way to the Maryland Heights overlook. Throughout the day, groundhogs ( Marmota monax ) often peek up from vegetation along almost any roadside within the park, while after dark, Virginia opossums ( Didelphis virginianus ) and raccoons ( Procyon lotor ) are more likely to be encountered in these areas.