Beavers are well known for their amazing engineering capabilities. Through the use of their unusually strong teeth, these aquatic rodents can fell small trees, which they use along with collected sticks to construct lodges and dams. The trees and sticks are held together in these constructions through the use of mud, which the beavers apply with their paws and their characteristic flat, paddle-shaped tails. Beavers also build burrows in banks and canals that aid them in moving the wood they have collected to the proper location. Such activities of the primarily nocturnal animals are instinctive, and those in captivity continue to carry them out although they serve no practical purpose.