Wild Ideas: Beavers: nature’s engineer

“I’m a big fan of the symbol of the beaver because I feel a country gets the animal it deserves. A beaver is an unaggressive, hard-working, waterproof, unassuming, wonderful animal and I think it speaks well of Canadians that we chose it.”

That’s what David Morrison, director of archeology and history at the Musée Canadien des Civilisations in Hull, Quebec, is quoted as saying in a 2011 article in the Huffington Post Canada. With the boom in fur trading now long gone, Canada was debating whether it should keep the North American beaver (Castor canadensis) as an official symbol of the country’s sovereignty. In any case, I think Morrison’s characterization of the beaver was apt.

Its long, scaly tail, webbed feet and thick fur make this beaver well adapted for aquatic living. Photo by Steve via Wikimedia.
Its long, scaly tail, webbed feet and thick fur make this beaver well adapted for aquatic living. Photo by Steve via Wikimedia.

The largest rodent in North America and second largest in the world behind South America’s capybara, beavers typically grow to three or four feet long (excluding the tail) and 30-60 pounds. The largest beaver on record is 85 pounds, according to the Virginia Fish and Wildlife Information Service.

At least 65 million beavers — possibly five times that number — were thought to have inhabited North America before Europeans arrived. However, by the beginning of the 20th century, the beaver was on the brink of extinction from overhunting for its musk (used in perfume and folk medicines) and luxurious fur.

With increased concern about nature conservation in general following World War II, beavers were reintroduced into many areas, including Virginia. By 1988 their numbers on the continent had increased to 12 million, making their recovery “one of the greatest conservation stories,” according to an article in the January/February 2003 issue of National Parks magazine.

Often called “nature’s engineer,” the beaver is second only to humans in reengineering natural ecosystems, and without them Virginia would have few naturally occurring ponds. Beavers create ponds to protect their lodges, which they build out of trees they gnaw down. Access to the lodges is under water.

The deep water also enables beavers to transport larger tree segments to the construction site. They will even dig canals to aid in such material transport. When they can’t build dams, beavers will dig tunnels that are 10-40 foot long in the banks of streams to use as dens, according to VaFWIS. Because of the steep gradient and rocky bottoms of streams at their headwaters, beavers are not usually not found in those areas.

While humans may not be happy with the beaver’s engineering, the ponds and wetlands it creates serve as habitat for many other species. When beavers move on, many of these wetlands convert to meadows, providing habitat to other species before forest takes over again. With this cascading effect, populations of many species rebound along with the beavers.

Humans should also value some of the ecoservices beavers provide, including the buffering effect on adjacent lands. The ponds and wetlands beavers produce keep water in the landscape for drier times and, during precipitation events, slow runoff and reduce flooding, capturing silt and pollutants in the process.

The beaver that had recently gnawed down a few tulip tree saplings at a pond where I live seems to have moved on, likely driven off by all of the human activity from the trout-fishing operation at the adjacent pond. While I didn’t get a chance to see this particular beaver, I’ve been lucky enough to observe others on various occasions.

The tulip tree sapling above, about 2.5 inches in diameter, was gnawed on by a beaver that stopped by for a few days. The stump next to it is all that remains of another sapling that the beaver gnawed down. Photo by Pam Owen.
The tulip tree sapling above, about 2.5 inches in diameter, was gnawed on by a beaver that stopped by for a few days. The stump next to it is all that remains of another sapling that the beaver gnawed down. Photo by Pam Owen.

One lone beaver that lived along the Hughes River at the same time I rented a place down there used to get my dog excited when we ran into it on our regular dawn walks. The beaver would warn us off by loudly slapping its tail on the river’s surface, a typical defense against intruders. Although beavers rarely attack humans, they can defend themselves with their long, sharp teeth when pressed, so they should be observed from a safe distance (like with all wildlife).

Well adapted to aquatic living, beavers have thick, protective fur and webbed feet. The flat, scaly tail, which becomes a lighter color with age, also serves as a rudder. Beavers can range up to 450 feet from water in search of food, but usually stick closer, according to VaFWIS.

During the summer, beavers mostly feed on herbaceous (non-woody) plants and leaves of trees, shifting to bark and small twigs later in the year. They cache twigs in their lodge to eat when winter ice prevents them from foraging. While beavers prefer aspens, they will feed on a variety of other trees, with willows and cottonwoods also near the top of the list.

Some targeted species, such as native willow, actually benefit from this trimming, which stimulates root growth and the spread of suckers. When a beaver is cutting branches below water, its lips close behind its front teeth, keeping water from entering its mouth.

When beavers come in conflict with humans, it’s often from the latter’s own attempt to reengineer the natural landscape. When building ponds, for example, people often clear forest, leaving or planting only a few specimen trees that the beaver may then target.

While nuisance beavers can be killed without a permit any time of the year in Virginia, depending on local ordinances, and trapping is allowed in most counties in the winter, landowners now have other less lethal methods for controlling them. These include providing more of a forest buffer around ponds so beavers are less likely to target specimen trees, and using protective metal cages around those. Environmentally friendly chemicals that repel beavers are also available.

Although they are nocturnal, beavers can occasionally be spotted around ponds and streams during the day, especially at dawn and dusk. They are monogamous and breed cooperatively, which is rare among mammals. Dominant males and females control mating within a colony of four to eight related individuals.

Mating starts in January and continues through March, with kits born in the spring. Two-year-olds leave the lodge or are driven out just before the birth of another litter. While they can move as much as 150 miles from their birth place, young beavers usually stick within a few miles of their parents.

Beaver facts

  • In 1855, American poet Henry Wadsworth Longfellow featured the beaver and its lodge in his epic poem “The Song of Hiawatha.” In the poem (available at hwlongfellow.org), Hiawatha pursues Pau-Puk-Keewis, who entreats a colony of beavers to turn him into one of them so he can enjoy their “pleasant . . . dwelling” and escape Hiawatha. The king of the beavers agrees, inviting Pau-Puk-Keewis into the beavers’ lodge and making him the colony’s leader:

Thus into the clear, brown water
Silently sank Pau-Puk-Keewis:
Found the bottom covered over
With the trunks of trees and branches,
Hoards of food against the winter,
Piles and heaps against the famine;
Found the lodge with arching doorway,
Leading into spacious chambers.

  • To quote James Thurber, another American writer,

“One has but to observe a community of beavers at work in a stream to understand the loss in his sagacity, balance, co-operation, competence and purpose which Man has suffered since he rose up on his hind legs. He began to chatter and he developed Reason, Thought and Imagination, qualities which would get the smartest group of rabbits or orioles in the world into inextricable trouble overnight.”

  • The term “eager beaver” came into common parlance in World War II, from officers’ characterization of zealous recruits.
  • According to one nasty bit of folklore, beavers were thought to “self-castrate” in order to deter hunters from killing them to obtain their musk for perfume and medicine.
  • After their extirpation from Great Britain 400 years ago, beavers were reintroduced there in 2008.
  • Although beaver attacks are rare, then can occur when beavers feel threatened or have rabies. According to an article in Britain’s The Telegraph, last April an angler in Belarus died after he was got too close to a beaver, wanting to have his photo taken with the animal. The beaver bit him twice on the thigh, severing an artery.
  • Hats, especially top hats, were once made with beaver fur. The changeover to using silk benefited more than just Fred Astaire, helping to ease the demand for beaver pelts.
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Pam Owen
About Pam Owen 278 Articles
Writer, editor, photographer, and passionate nature conservationist living in Rappahannock County, in the Blue Ridge Mountains of Virginia. Two favorite quotes: By E.O. Wilson, who coined the term "biodiversity," "Nature holds the key to our aesthetic, intellectual, cognitive and even spiritual satisfaction”; by Douglas Adams, “I love deadlines. I love the whooshing sound they make as they pass by.”

3 Comments

  1. Great article! Yes Pam, there are many of us who respect and love beaver critters. The habitat they create is amazing.

  2. Great article! I wish more folks would realize that beaver flooding and chewing can be solved without trapping so that they could see the effects of their engineering first hand. My own city was worried about a local beaver dam and installed a flow device to control pond heigh, which solved the problem and allowed the family to remain. Now because of our beaver-tended wetlands we regularly see otter, steelhead, woodduck and even mink in a little urban stream!

    Heidi Perryman, Ph.D.
    Worth A Dam
    http://www.martinezbeavers.org

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