One of the most common mammals in the park is the Richardson's Ground Squirrel (Spermophilus richardsonii). Because it often stands erect on its hind legs to survey its surroundings, Richardson's Ground Squirrel has acquired the nickname "Picket Pin." It is also called "Flickertail," for the way it accompanies its shrill whistle with a flick of its tail.
They are often mistaken for Prairie Dogs, however they are a little smaller. Richardson's Ground Squirrels are 8-10" body, 2-4' tail. They are solid golden brown, undersides are pale or white; No Stripes.
Although they are a rather solitary species, Richardson's Ground Squirrels sometimes lives colonially in favorable habitats, and is especially abundant where vegetation is short. In addition to its shrill whistle, this species also produces chirps, churrs, squeals, and tooth chatters. Its major predators are badgers, weasels, gopher snakes, hawks, and coyotes. These animals eat green vegetation, insects, and sometimes carrion. They have an extensive burrow for shelter and food storage. This ground squirrel hibernates from September to March.
The squirrel was named after the Scottish naturalist Sir John Richardson.
North Dakota is nicknamed the Flickertail state after the squirrel.