The beaver is the largest rodent in Canada, weighing anywhere between 15-35 kg, the
beaver had a huge effect upon the exploration, development and history of the Canadian nation. Due to a demand for the beaver pelt (skin or hide) as a textile (fabric or cloth) material in Europe beginning in the 18th century, it was the beaver that sparked the
detailed exploration of North America and provided the driving force for the establishment of the lucrative fur trade economy that became the basis of the Canadian nation. The Beaver has, as a result, become a Canadian national symbol.
Beavers are Canadian symbols, but they are also good symbols of the environmental needs of wildlife. An average sized adult beaver weighs about 20 kilograms or 45 pounds: not the largest animal in the Boreal Forest, but far from the smallest as well. Typically beavers live in family units of two adult beavers and 3-4 kits. Year old beavers also usually remain with their families so the average will house about 6 animals.
What makes beavers remarkable is the way they adapt their habitat to meet their needs. The dam is perhaps the most obvious example of this. Typically built across a slowly flowing river or stream, beaver dams are often 45 metres long (150 feet) and two metres (6 feet) high. They can be up to 3 metres or about 10 feet wide at their base. This dam needs to be large enough to create a pond 2 to 3 metres deep; deep enough that it will not completely freeze to the bottom even in the coldest winters. Built of branches, stones, roots and mud a typical dam will consist of about 250-280 cubic metres of material. But that is not all a beaver needs. A beaver lodge that is 2 metres high and 6 metres (or 20 feet) in diameter will need another 20 or more cubic metres of material. In total then, every beaver family needs enough lodge and dam material to fill the main floor of a small two bedroom house. No wonder the term ‘busy beaver’ is used in Canada!
In addition, beavers need food: about 1.5 pounds of pond vegetation, leaves, buds and bark from trees every day. The favourite food of beavers is the inner bark, or cambium, of the aspen or poplar tree. Naturalists estimate that each beaver colony will need over 200 trees a year for food and building material. These trees also need to be located close to the pond because of predators.
So beavers need a lot of boreal forest: flowing water to dam into a pond, lots of building material, and plenty of food located close to the pond. It is not easy to find the right conditions, so only a small part of the boreal forest is really suitable as beaver habitat.