North American Beaver

The beaver is an absolutely fascinating creature with its highly industrious engineering skills and single-minded pursuit in creating intricately designed dams and living quarters. A beaver dam is an impressive construction to see, not only does it take an exhausting amount of work to build and maintain it but the structure itself is so well built that human engineers have replicated their curved design to build more successful dams themselves. They are a perfect example of how much we can learn from the natural world!

Here in Calder we have a number of ponds and waterways, including three interlinked ponds at the northern end of the property, known as the Three Ponds. It’s a magical area where we love to spend time and is made all the more interesting by the very busy beavers that also call it home. There has been one or more beavers living in the second pond for a few years now, who have built themselves a lovely lodge there and a sturdy dam obstructing flow between the first and second ponds. This summer at least one more beaver, maybe a whole family, moved into the area and dammed up the stream below the third pond, creating a large pool, and built themselves a lodge at the far end in a very short amount of time. Beavers are most active at night, so hard to spot, but sometimes we get lucky if we visit at dusk and see them emerge from their homes to begin their evening’s work. If they spot us they give us a warning to keep our distance by slapping their wide, flat tails on the surface of the water and quickly dive down out of sight.

The purpose of the beaver’s dam is mainly for protection from predators. The dam stops the water from flowing in creeks and rivers and creates large, deep ponds upstream of the dam in which the beavers can swim underwater and avoid detection and capture by hungry coyotes, bears or bobcats. It also ensures that the deeper ponds will not freeze in the middle of winter so that the beavers can still access the underwater entrances to their lodges. The beaver, which can hold its breath for up to 15 minutes, can then swim for long stretches hidden below the surface of the water and travel safely from the ponds edges to inside their lodges. The dams and lodges are constructed using a mixture of sticks, mud and stones salvaged from in and around the ponds. In order to gather all the wood they need these large rodents make short work of felling nearby trees by using their oversized front teeth to chew around the base. They then use their dexterous front paws to help in moving the chewed-off branches to where they are needed. If a dam is breached the beavers quickly repair the hole using more sticks and mud. A study was done to see what triggers the beavers to know when and where there is a breach, the researchers placed a speaker near a beaver dam and played the sound of running water. The hilarious and insightful result was that the beaver completely covered the speaker with sticks and mud until the sound was completely muffled!

The lodges are built by first creating a large pile of sticks at the edge of, or in the middle of, ponds. They will then chew through these sticks to build underwater entrances leading up to one or two dry platforms inside, above the waterline. To help them in these aquatic endeavours, beavers have a neat feature in that they can close their lips behind their front teeth which enables them to chew underwater. They then cement the whole construction together using mud gathered from the pond floor. As a final touch, they even have the ingenuity and foresight to leave an air hole in the roof of the lodge. Master builders, indeed!

Another purpose of the dams is to store food for the winter months. Beavers feed on leaves, buds and the inner bark of trees and in order to keep themselves well fed throughout winter they create an underwater food cache by storing branches at the bottom of the dams, sticking them into the mud to keep them safe and secure until they need them. The stored branches can then be easily retrieved when the ponds are frozen over by swimming underwater from the lodges to fetch them from the dam and consume them back in the safety and warmth of their homes without ever having to leave the ponds. Pretty clever again!

Beavers will move on when the food source near the ponds is depleted so we are enjoying our resident families while they are still with us. Because of their nocturnal habits they are a difficult one to get photos of but we will keep trying and hopefully get some good shots soon that we will post. In the meantime here is a short video of the few times we did manage to capture them with our trail cameras. We had one of the cameras trained on a tree that they were chewing on, hoping to get the eventual “timber” shot but in the end it came down on a stormy, windy day instead. All part of their plan, for sure!