American pikas are donut-sized members of the rabbit family that are especially vulnerable to global warming because of their specific habitat requirements. Prolonged periods of high temperatures can prove lethal, and without winter snowpack to insulate them, they can freeze. Pikas are also restricted to small, disconnected habitats, which prevents them from moving to more favorable climates. Entire populations have already disappeared from parts of North America's Great Basin.
Why they're in trouble: