At one point hundreds of millions of black-tailed prairie dogs populated central North America, from Texas to Canada, living in colonies of tunnels that stretched for miles. Eradication programs and habitat destruction have decimated prairie dog populations by as much as 95 percent, as ranchers and farmers have tried to rid their properties of the burrowing animal. However, prairie dogs are considered a keystone species, and an important prey animal for numerous other species. Ecologists also consider prairie dog burrowing as beneficial for the long-term enrichment of soils.
The black-footed ferret is one of the most endangered species in the United States. It is a part of the weasel family and depends on prairie dogs for 90 percent of its diet. It is nocturnal, hunting sleeping prairie dogs as they lie in their burrows. Loss of prey and habitat has brought the black-footed ferret to the brink of extinction. In the 1980s, remaining wild ferrets were taken into captivity to initiate a captive breeding program, with hopes of reviving the species. At this time there were only 50 animals remaining. The program has so far been successful, with ferrets reintroduced into the wild, starting in 1991. As of 2007, U.S. black-footed ferret populations included 650 in the wild and 250 in captivity.
As of 2011, there were approximately 400 whooping cranes in the wild. The tallest bird in North America, many whooping cranes winter in Canada and travel to Texas and areas around the Gulf of Mexico for the summers, making the central U.S. an important migratory route. From a population of over 20,000 cranes, the population dropped to a low of 15 in 1941 due to habitat loss and hunting. Conservation efforts have led to a slow and steady recovery, although the whooping crane remains critically endangered.
The pallid sturgeon is a large, ancient fish that is native to the Missouri and lower Mississippi rivers. An adult sturgeon can weigh up to 80 pounds, and live 30 years. Dams and other engineering efforts have significantly changed the nature of the Missouri River, reducing the availability of food for sturgeon, and making it more difficult for them to spawn and reproduce. According to the U.S. Fish and Wildlife Service, 28 percent of the sturgeon's habitat has been made into lake-like conditions, 51 percent into deep and uniform channels, and 21 percent is downstream of dams. Because sturgeon spend considerable time on the bottoms of rivers, environmental pollution has likely played a role in their decline.