After 150 years of poisoning and shooting them, humans are slowly recognizing prairie dogs as more than a pest. The public started to change its perspective in the 1990s, says Ana Davidson, a conservation scientist with Colorado State University in Fort Collins. Around the same time, biologists asserted their status as a "keystone" species that links plants and animals together in a vast grassland food web. Coyotes, badgers, raptors, and black-footed ferrets (a species at the brink of extinction) all eat prairie dogs. Digging burrows also moves the soil around, helping cycle nutrients, which has been linked to healthier, more nutritious grasses for grazers like bison and cattle. And their burrows create habitats for burrowing owls, tiger salamanders, spiders, and insects. All in all, ecologists estimate that more than 150 species interact with prairie dogs in some way. That means these little rodents and their burrows form the foundation of North America's greater grassland ecosystem—one of the most endangered ecosystems in the world.