From bison to badgers, ferrets to ferruginous hawks, black-tailed prairie dogs play an important role in creating a grassland habitat that supports dozens of other species. "As keystone species, prairie dogs lie at the heart of a network of ecological interactions," says Smithsonian researcher Andrew Dreelin. But prairie dog numbers have been declining for decades, and scientists believe the black-tailed prairie dog is down to just 2% of its historic range. How does this impact the species that