North American beaver in a pond near Wonder Lake, Denali National Park, Alaska

© Paul Souders/Getty Image

North American beaver, Denali National Park, Alaska, USA

Meet the beaver: part-time lumberjack, full-time architect and all-around ecological superstar. Known as nature's engineers, beavers have been shaping the world for millions of years. Historically, North American beavers—seen in today's image—faced challenges from humans. They were hunted for their fur, and their 'nuisance' freshwater abodes were destroyed. However, these buck-toothed, paddle-tailed dam builders have been gaining new respect in recent years. Beavers are the second-largest rodents after capybaras. These animals have beneficial effects not only on water quality but also on land. With their iron-coated orange incisors, beavers fell trees, diligently constructing not just homes but habitats. Their dams create life-sustaining wetlands for countless species. The beavers' own lodges are masterpieces of security and comfort, with the entrance strategically submerged to deter predators and provide privacy.