4. Bog turtles
Federally listed as endangered in 1997, the diminutive bog turtles live in fractured swampy habitats across North America. "We do have some concerns because the species is impacted by small changes in temperature, and its habitat is driven by freshwater springs," says wildlife manager Michael Horne in a U.S. Fish and Wildlife Service report. The turtles' nesting sites sit very close to the surface of the bogs where they live -- should these areas flood in the summer, the nests are at risk of washing out.