PHOTO: Matteo Tarenghi/Flickr
Karen Lanier
August 6, 2018

Beavers know water. They are semi-aquatic rodents with extreme hydro skills. They are equipped for living in, around and under water with all kinds of cool adaptations: nictitating membranes that protect their eyes like goggles, ear and nose flaps that close to keep water out, and a thick rudder for a tail. The key feature that almost led to the extinction of the beaver was its waterproof fur—the thick pelt and the waterproofing agent.

The beaver’s scientific name, Castor canadensis, hints at the special ingredient, castoreum, that was highly valued as a perfume fixative in the 19th century. Not to be confused with castor oil, the aromatic secretion is produced from a sac near the beaver’s anal gland, and distributed via combing with a special, split claw on the second toe of the animal’s webbed, back feet. The oily coating on beavers’ fur keeps them dry even when submerged, and it might have been one of the selling points for beaver hats. Like many beautiful birds whose feathers filled women’s hats, the overharvesting of beaver for fashion and perfume drove populations dangerously low.

Beavers are not only equipped to live in water, they are expert architects of underwater abodes. Beavers are industrious natural builders, making the most of simple materials: wood, mud and water. They can gnaw a small tree down in 20 minutes with their sharp incisors, then use the leaves, twigs and soft inner bark for food and the woody parts for building materials. Cordwood home builders look to the beaver lodge’s natural design for clues on how to build earthen homes with stacked logs and thick, insulated walls. Beavers don’t hibernate, and they use the ponds that their dams create as a deep, cold (but never frozen) storage space where they stash branches for winter food. These ponds also provide protection by covering the entrance to their lodges with water. Muskrats benefit from the beaver lodges too.

beaver beavers trees
Andrew Malone/Flickr

Beavers are landscape ecologists as well. The structures they build affect entire ecosystems, which is why they’ve been named a keystone species. The beaver’s relationship with woodlands and wetlands is complex and requires decades of observation to fully understand the effects. For example, some trees such as aspen will sprout new growth from the stumps that remain after a beaver has chewed it down. The new growth contains naturally occurring defensive chemicals in a more concentrated amount to repel future beaver nibbling. The new-growth trees succeed in surviving while beaver move on to a different individual or acquire a taste for a different species. Also, beaver can speed up the succession of forest growth by thinning out standing trees, allowing sunlight to penetrate and nourish young seedlings. Likewise, they can eat so many native trees that invasives get an advantage.

Many factors play into whether beaver contribute to overall health of a wild forest or exacerbate problems. In northern regions, a family of beaver has been estimated to remove a metric ton of wood from within 100 meters of its pond in a year. Beaver favorites include alder, aspen, apple, birch, cherry, cottonwood, poplar and willow. Beaver habitat should include plenty of space to buffer the animal’s activities.

If you have beaver on your property and want to find a way to live with these semi-aquatic architects, explore these solutions:


Lessen Water Sounds

Beavers build dams in response to the sound of running water. If you can stop the sound, you can probably stop the dam building. Michael Callahan with Beaver Solutions designed devices that work inside beaver ponds to keep the flow moving without the sound while keeping the pond at a certain level. His work has been particularly effective on culverts.

Fence Your Trees

Install a 2-by-4-inch wire mesh fence to encircle the trunks of vulnerable trees. Take into account the level of snow in the winter, and the fact that the animal can stand on its hind legs to gnaw, so it should cover at least 2 feet in height.

Protect an Orchard With Electric Fence

This works well for land that isn’t level, where roll-out fencing is a hassle, or there are too many trees to fence individually. The electric wire should be placed 4 inches off the ground.

Paint Your Trees With Sand

Mix 50/50 sand and latex paint. Beaver teeth might be strong, but they are also very sensitive. The gritty feel of the sand repels beaver from chewing the painted trees. Make sure the paint you use is non-synthetic and doesn’t contain mercury.

For more information on the beaver-prevention practices listed here, and to learn more about coexisting with beavers, see the Beaver Institute.

If forests are the “lungs” of the planet, then wetlands are the “kidneys.” They are the vitally important filters of surface water that support all life on Earth. With proper management, wetlands can undo some of the pollution caused by conventional farming practices. Beaver ponds are effective at removing excess nitrogen and phosphorus from fertilizer runoff, as well as holding back sediment that adversely affects aquatic life. Working with native species such as the beaver can open up possibilities that will benefit your farm and the future of water quality right where you live and farther downstream.


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