Beavers are social mammals who live in groups, known as colonies, and they construct dams and lodges, which modify the surrounding landscape. In their role as “ecosystem engineers,” beavers are considered to be a “keystone” species. A keystone species is one that has such a major impact on its ecosystem that the ecosystem would be vastly different without that species in it. Removing a keystone species from its environment can lead to major changes throughout the ecosystem from disruption to collapse.