A wide diversity of animals make their home within the boundaries of Theodore Roosevelt National Park. An abundance of native grasses provide sustenance for larger grazing animals: bison, elk, pronghorn antelope, white-tailed and mule deer, bighorn sheep and feral horses. Once land is grazed or disturbed, it becomes prime habitat for prairie dogs to build their towns. The park's prairie dog towns are a great place to find birds feeding on seeds, burrowing owls making their dens, and prairie rattlesnakes or bull snakes living in abandoned burrows. It is not uncommon to see a golden eagle flying overhead, or a porcupine ambling up a tree to snack on the tree bark. These along with many other animals make wildlife viewing a popular activity in the park.