An adult beaver can grow up to one metre in length and weigh as much as 30 kilograms. These animals live in river valleys and near slowly running or standing water. Their presence can be noticed by chewed tree bark and by their dams, constructions of branches, leaves, and mud. Beavers are vegetarians. In summer, they mainly eat water plants, leaves and branches, while in winter they subsist on bark. On land they move gracelessly, but in water they are fast and agile. They are excellent divers. They are able to close all of their body openings and stay underwater for as long as 15 minutes without a break! While diving, they are supported by their tails, which are covered in scales and act as a rudder.