Also, during winter a bank den provides an air pocket and can lengthen the time away from a lodge for a beaver swimming under the ice when it needs a breath of air. While beavers are creative in building their homes, they are at their best in constructing elaborate water control projects. They build dams to raise water levels and then cut canals, make plunge holes, dig underwater aqueducts and dredge channels into the bottom of ponds. Damming the flow of moving water is the strongest instinct a beaver seems to have outside of eating and procreating. Most dam building occurs in early spring and late summer and, typically, most of the work is done at night.
Beavers create excellent habitat for other animals too, such as moose and waterfowl.
Beavers breed in January or February and following a gestation period of about 100 days, the female bears a litter averaging four kits. The kits weigh about a pound at birth and are a little more than a foot long, including the tail. They are fully furred, their eyes are partially open, and their incisor teeth are already in place. The mother frequently grooms and nurses the kits. In the wild, beaver live 10 to 12 years, and, unlike most other mammals, beavers continue to grow throughout their lives.