Over the last few years, we’ve become aware of North American Beavers (Castor canadensis) patrolling two parks in the township – Cranberry Lake and Draper Twin Lake Parks. Cool! I’d seen a lodge, signs of beaver activity and what appeared to be a beaver at a distance swimming across Cranberry Lake as you’ll see below. And then the birding group spotted a beaver swimming toward the lodge one morning this May. The glinting sunlight on the water and the distance made photography impossible that day and I missed taking a photo of one swimming toward me the next morning when a family member called my cell phone at a critical moment. The wily rodent slipped into the reeds and did not come out again. Drat!

Check out this slide show to see signs of beavers that I’ve found in our parks in recent years.

This spring, an American Beaver (Castor canadensis) caused some concern at Draper Twin Lake Park when it built a small dam where the Twin Lakes drain into a wetland; the water level rose and flooded people’s property. Some of the lakefront homeowners approached our Stewardship Manager, Dr. Ben VanderWeide, about the problem. Ben suggested installing a “beaver baffle,” a device that helps control water at an appropriate level by sneaking water through the beaver dam. (More about that later.)

Now all of that happened at a fortuitous moment for me.

I had recently come across a new book about – you guessed it – beavers. Beaverland: How One Weird Rodent Made America by Leila Philip kept me engaged for a week with great info about this fascinating animal that I’d only briefly glimpsed. So I’m about to regale you with a taste of what I learned about North America’s largest, very likable, and at times very exasperating rodent!

[Many thanks to Draper Twin Lake Park neighbor Maureen Moons for a photo of our Draper beaver, Bill Beverly for the trail cam photos, neighbor Terry Nowels for her flooding photo, Joan Bonin for her local beaver photos, and the generous photographers at iNaturalist.org and Wikimedia.com.]

The Disappearing-Reappearing-Disappearing History of the American Beaver

According to Beaverland, one million years ago, beavers the size of bears roamed North America. These extinct Giant Beavers (genus Castoroides) inhabited the late Pleistocene along with other megafauna, like saber-toothed tigers, giant sloths and huge armadillos. Our American Beavers, which are distant relations of the Giant Beavers, also lived at the same time as Giant Beavers. According to Wikipedia, Giant Beavers could be 6-7 feet long and weigh between 170 and 250 pounds. Typical American Beavers average about 44 pounds and their bodies, excluding the tail, are about 3 feet long. Since beavers never stop growing, though, old ones can get larger.

After the glaciers receded, the landscape flooded then dried out and Giant Beavers became extinct. But our smaller American Beavers survived and thrived. They set off to remake the American landscape with their dams, which held water on the land, creating rich wetlands, marshes and lakes. They created channels through regrown forests to transport logs for their dams, creating new streams and even rivers while harvesting acres of trees. After surviving the Ice Age, they were in their heyday. As many as 100 -200 million beavers got to work adapting the North American landscape to meet their needs.

Most of us know the next part of the tale. According to Philips, “the Oneida, Huron and Iroquois had been trading [beaver pelts] among themselves for centuries, ” But extensive trapping by Europeans began in the early 17th century and continued unabated until the mid-19th century. Beaver pelts, Philip reports, especially the “dark and lustrous ones from “trading centers of Detroit and Michilimackinac sent London prices skyrocketing.” Fashionistas of the 19th century were not just interested in the shiny, water-resistant outer layer of beaver fur used for fancy collars and warm hats. Nineteenth century milliners paid top dollar for the dense, insulating inner layer of beaver fur with its interlocking barbs which they used as the smooth, shiny surface of luxurious top hats for the rich and famous.

Beavers probably survived in part because beaver fur was replaced by silk for top hats in the mid-19th century. Some state and local protections for beavers were passed in the late 19th and early 20th century, but to this day, beavers are still widely trapped. In Michigan no bag limits apply to beavers taken in season, and beavers were recently added to the list of nuisance animals that property owners can kill without a permit.

But despite advancing glaciers, the great floods at the end of the Ice Age and near extermination by fur traders and their milliner customers, about 10-12 million beavers still inhabit the waters of North America. Whew! It’s amazing they’ve lasted long enough to show up in our parks! I’m glad they made it to the 21st century.

Today’s Beavers – Equipped for Survival!

Perhaps the American Beaver survived because of their unique anatomical and behavioral adaptations. They outlived the Giant Beavers who probably ate submerged aquatic plants like our beavers. But tests on their fossil’s teeth indicate the Giant’s teeth couldn’t chomp into trees so it’s not known if they built lodges or dams, both of which serve as survival strategies for beavers. Modern beavers also feed on aquatic plants and leaves. For example, they often store the rhizomes (underground stems) of water lilies inside their lodges for winter meals. When cold weather sets in, they can also dine on the inner bark and cambium of trees using their bright orange, iron-fortified front teeth which grow back continually like the teeth of all rodents.

The beaver’s broad, paddle-shaped tail is the original multi-tool. The extinct Giant Beaver’s tail resembled the tail of our muskrats, round and thin. Today’s beavers’ paddle-shaped tails help cool them in the summer through the tails’ blood vessels and provide nourishment from the fat stored there if food is scarce during the winter. Our American Beavers are also famous for slapping their tails on the water to warn their families of danger. An exceedingly useful tail, wouldn’t you say?

Their dexterous forepaws allow them to fold leaves into their mouths, dig for food, groom fastidiously and rotate small sticks while gnawing off the bark. (Click on photos to enlarge.)

Beavers swim efficiently, too. Their very large webbed back feet and those useful tails propel them smoothly and quickly through the water, with the tail doing most of the steering as they thrust left and right. Clear membranes slip across the eyes to function as goggles when beavers dive, improving their vision in often muddy water. Their ears and noses close under water and a second set of lips behind their teeth allow them to open their mouths and chew when submerged. And because their eyes, ears and nose are all high on their head and aligned forward, they can cruise along the surface with their heads barely visible and their bodies submerged – a good defense against predators.

But probably the biggest survival adaptation for our beavers is their ability to change the environment around them. When the earth began to warm about 12,000 years ago after the Ice Age, the Giant Beavers lost many of the wetlands on which they depended; prairies and forests reclaimed the land. But the modern beavers set to work changing the landscape by creating wetlands, ponds and lakes with their dams – and luckily lived on!

Home Life for Beavers

Wikipedia explains that beavers construct their lodges out of sticks, twigs, rocks, and mud. Within they create two platforms, one space for drying off and another as living space. A small air hole is left in the top and an underwater entrance provides security. Predators like coyote, mink and in other regions , black bears or mountain lions, must try smashing their way into a beaver lodge, and that’s not easily done.

According to the documentary, called “Leave It to Beavers” on PBS’ program, “Nature,” beavers are monogamous and live in family groups. They mate between December and May and have from three to six kits. The youngsters have a lot to learn about foraging, felling trees and constructing lodges and dams – so they generally stick around for an average of two years before they head out on their own and mate.

In wintry locations like ours, beavers usually create a food cache in the fall by felling trees, collecting branches or small trees and then sticking them into the muddy lake bottom. Ice forms around them, but the protruding branches catch enough warmth from the sun to keep the water around the cache open , so the beavers can forage on them while under water or tow them inside. Some branches may be conveniently stuck into the lodge itself to be chewed on during the winter. In the photo above this section, taken at Cranberry Lake Park, you can see a bare branch stuck in the ice next to the lodge and branches protruding from it.

Now, About Those Dams…

Nothing motivates beavers more than the sound of running water. It’s like a siren going off – and not just in their ears! Those amazing tails also register a change in water pressure as the sound reaches them and any beaver in the area makes a beeline toward that sound.

Why? Dams are crucial to beavers because they need deep water near or around their lodges. Deep water protects them from predators but also means that it’s less likely that the pond beneath their lodge will freeze solid. Beavers need to leave their lodges to forage, escape and breathe during the winter. They can tolerate some ice by slamming their heads up against it from below to break a hole when or by finding an area just under the ice where air is trapped so they can breathe while hidden. Dams do the job of deepening the water enough to assure their survival.

The Pros and Cons of Beaver Behavior

First the Good News…Beaver Benefits

In her book Beaverland, Leila Philip reminds the reader that many of the ponds, rivers and lakes we enjoy were probably originally created and/or maintained by beavers. “Scientists call beavers ‘ecosystem engineers,’ meaning they create new habitats, new ecosystems when they build their ponds… Great blue herons stalk the shallows and red-winged blackbirds herald in the trees. In the highest points, osprey nest… Water from beaver-altered streams and wetlands has been measured to contain fifteen times more plankton and other microbial life than wetlands without beavers.” Tyler Brown in a video from Vermont Fish and Wildlife also mentions that beavers create habitat for all kinds of creatures – “moose, otter, a whole host of songbirds, water fowl, fish, amphibian and reptiles.” We benefit too as the beaver-created or maintained wetlands recharge our aquifers, filter out pollutants, help control floods and keep water in drought-ridden areas. For example, according to the “Leave It to Beavers” documentary, after reduced cattle grazing and fur trapping along Nevada’s Susie Creek, returning beavers turned a desert back into twenty miles of healthy habitat for wildlife, including mule deer, sandhill cranes and native trout. Beautifully green vegetation now covers over 100 acres, open water extends over 20 acres and the stream has been lengthened by almost three miles. An incredible restoration project engineered by human-beaver cooperation!

Now the Not-So-Good News – Beaver Problems

Obviously, beavers can also cause difficulties for humans. To build a dam or lodge, and to eat during the winter, they fell trees. An adult beaver can fell and tow a hundred pound sapling to a dam site – against the current! A five inch diameter willow can be felled in six minutes. Needless to say, tree felling isn’t always appreciated by humans who generally love trees. And as the water level rises, a piece of private property can disappear beneath the pond’s surface. If the sound of running water comes from a culvert or drainage ditch, beavers may persist in plugging it up to stop what they perceive as a completely unacceptable sound! Roadways, driveways, yards and septic systems can begin to flood. So what do we do? Sometimes, beavers must be professionally transported to new areas, but that’s rarely a long-term solution. So …

The Solution to Dam Issues in One of Our Parks Might Be Baffling the Beaver!

This spring some residents around Twin Lakes reported a rise in the water level from beavers that had been busy in the lake since about 2019. Sure enough, the small dam that appeared in 2020 had been heightened and water had risen about 18 inches in the lakes.

Ben researched solutions that would get the water level down while keeping beavers in the lakes to continue doing their helpful wetland habitat work. Killing or trapping beavers is rarely a long-term solution. Constantly tearing down the dam is a lot of work, and just invites the beavers to continue to cut down trees and shrubs to repair the damage. He recommended installing a device in the dam called a “beaver baffle” as a better solution. After meeting with the neighbors and the Park Commission’s Stewardship Committee, maintenance and stewardship staff gave it a try.

To work, a beaver baffle needs to prevent the sound and feel of water flowing. To accomplish that, a large round pipe inside a cage is placed in the water on the upstream side. A notch is cut into the dam for the pipe and the other end is immersed downstream beyond the dam. As a result, the water can drop slightly in the lake for the homeowners, but we hope, still satisfy the beaver’s need for deeper water. A win-win situation if all goes well.

On April 30, just before the baffle installation, the dam was notched to lower the water slightly to make it safer to work. Water began to flow into the wetland downstream from the dam and a trail cam recorded the flow.

Bill Beverly, a Draper neighbor and Parks Maintenance Technician, assembled some nighttime photos from the trail camera of the beaver busily piling sticks on the breach, while a Great Blue Heron looked on. I can’t spot the beaver in the video (except for a few bright spots to the left when the light hits its eyes?), but I can see the heap of branches growing rapidly! A lot of work on the night shift!

On May 1, stewardship and maintenance staff initially installed two baffles to get the water levels down, providing quick relief to lakefront neighbors after the recent heavy rains.

The trail camera also got wonderful shots of the progress of the beaver’s work over the following nights with the pile of sticks growing denser from May 6 to May 7. It also looks as though the dam is attracting wildlife! On May 6, the Great Blue Heron (Ardea herodias) checked out the repair work and the next night, two adult Sandhill Cranes (Grus canadensis) with their tiny “colt” (baby bird) explored the beaver’s handiwork.

For Now Our Baffle Seems To Be Working!

I went back to the site weeks later and all seemed to be well. The water level had dropped about a foot. Two pipes were no longer necessary to maintain the water levels, so one had been removed.

The remaining pipe with the cage was not blocked and a quiet flow of water was leaving the pond and flowing into the greenery of the wetland beyond. The beaver was not bothering the remaining cage or pipe. You can listen below to the water and note the call of resident Red-winged Blackbirds in the background.

Beavers and Humans Have One Big Behavior in Common?

Most animals have to adjust to the environments in which they find themselves. But, as Leila Philip says in her book, “Beavers, like humans, dramatically alter the landscape to create the environment they need (or want).” Both species have the ability to radically change the world around them – for better and for worse.

Beavers, though, will always be beavers. Their ability to change their behavior is dependent on thousands of years of evolution. And their numbers are limited by predation from other animals, including humans. Humans have few natural controls on our constantly burgeoning population and many of the changes we make for our habitat needs (or simply our preferences) have been harmful to the rest of the natural world . Unlike the beavers, we are now aware of the harm we have done and continue doing. And unlike most other animals, we’re blessed with the capability to quickly change our behavior.

Decades ago, visionary citizens in Oakland Township recognized that our local natural areas needed help. They began by protecting open areas from development through our Parks and Land Preservation millages. And since then, our Parks and Recreation Commission has worked to restore and nourish the habitats in which we live. Our stewardship staff monitors and removes invasive and non-native plants (even glamorous ones!), harvests and plants native seed, monitors bird, plant and insect populations, and much more. We work to heal the habitats in our township – prairies, forests, ponds, lakes, vernal pools, and wetlands – that we unwittingly damaged over time.

Now we know that human-caused climate change is bearing down on our natural world all over the Earth. We humans can change our ways quickly if we choose, unlike our dam building friends, the beavers. If we support the visionaries, scientists and leaders making those changes, bear the costs of doing so and quickly adapt our own behavior, perhaps we can restore the health not just of our local patch of earth, but that of our whole beautiful planet. Thanks to all of you who take action as a partner in that process!

RESOURCES

• Beaverland: How One Weird Rodent Made America by Leila Philip, published by Twelve/Hatchette Book Group, NY, 2022
• “Leave It to Beavers” a documentary on the PBS program, Nature, May, 2014
• “Beavers: Nature’s Wetland Engineers” – article by Natural Resources Defense Council
• Vermont Fish and Wildlife Video on installing water control devices, on YouTube
• Others as cited in blog.