If you are a persistent reader of my outdoor essays, you may recall the 2018 review of the American beaver, Castor Canadensis (link here). In that story I shared a memorable interaction with wild beavers at a small pond in Utah, along with the history and profile of these amazing creatures. I am revisiting the beaver in this article because of a trip in northern Maine where friends and I observed the significant impact of beavers on an ecosystem long after the beavers have moved on.

In the earlier article I described how beavers use their amazing engineering talents to reshape streams through the use of dams. Programmed from birth to impound running water, beavers apply themselves diligently to building durable dams, creating ponds that may last many years. Using four razor sharp front teeth, beavers are capable of cutting down everything from small saplings to sizable trees.

The process of building a dam starts small and low with beavers working in the main flow of a stream to begin backing up a small amount of water. Hour after hour, day by day, the beavers add additional material to the nascent dam using their teeth, small front legs, and tail to move sticks, grass, weeds, rocks, and mud into place. Beavers are highly attuned to the sound of running water, and any leaks in the new dam are immediately dealt with to continue raising the water level.

As the pond expands, the beavers are forced to widen their efforts in order to capture any water running around the ends of the dam. In an ideal location, the beavers will eventually extend the dam onto the sloped sides of a stream or valley, using the banked earth to help support the weight of all that water. You can imagine that a beaver pond of any size, for example 100 feet wide and five feet deep, means there are many tons of water pushing against that dam.  When rain water or snow melt comes rushing down the stream, the demands upon the dam are even more significant, and of course, sometimes the water wins and the dam fails.

Building such dams requires weeks or months of effort, and also ongoing maintenance to keep the dam in good shape.  There is safety in the water for beavers so they are highly motivated to secure as much as possible. There must be sufficient depth to ensure open water under the winter ice or the beavers will not survive. At the same time, during the few months between one winter and the next, the beavers have to create shelter, in the form of a log house or bank den, and they have to secure large volumes of food underwater. All this wood harvesting means the beavers have to work further and further from the dam to find enough trees and shrubs. While beavers are very capable in the water, on land they are slow and poorly equipped to defend themselves against predators such as bears, wolves, coyotes, and cougars.

If there is enough suitable vegetation within reasonable distance of the pond and stream (100 – 200 yards), a beaver colony may remain active for years. Eventually, the beavers exhaust the ready supply of building materials, or they succumb to predation, with the result that the dam is abandoned to the elements. Beaver colonies are serial builders so they move up or downstream in search of the next suitable dam site, sometimes supporting multiple dams simultaneously. If no good sites are available, the beavers are forced to travel overland and hope to avoid danger.

In my articles and presentations, I often refer to the importance of beaver pond habitat to a wide variety of species around streams. One of those creatures, the eastern moose, has presented me with several opportunities to camp in the great outdoors of Aroostook County on a wonderful large forested property owned by good friends. Thanks to winning licenses in the Maine moose lottery, my son, friends and I have traveled six hours to the area around Van Buren to set up camp in the midst of peak foliage season, generally with fine early autumn weather.

Among the roughly 3,000 acres of this forest, the prime habitat for moose is closely related to water. While we cover most of the forest with our scouting and hunting efforts, time and again we are drawn back to the small streams and the associated beaver ponds simply because that is where we find most of the moose activity. A hunt in 2008 found us next to a beautiful pond, and success came at 6:05 AM on opening day with a bull we had spotted there with a cow the day before. Several years later my son was nearly trampled by a giant bull in that spot even though the dam had failed, and a friend harvested his bull there 12 years later.

In 2018 I was back with a moose tag, and my friend Craig directed me to a newly built pond further downstream. In two days of scouting, it became obvious that every moose in the area was using the pond for drinking, feeding, and crossing the valley. It was no surprise that in three days of hunting I was fortunate to see four bulls and to harvest a fine bull on the edge of that pond. The beavers went on to build two more dams downstream and my friend Rob harvested his bull just up the slope from the second pond in 2022.

My luck in the moose lottery held so I found myself in Van Buren again this year in late September.  The foliage was just spectacular, probably the best I have ever seen in Maine, and the weather was generally perfect for being outside or camping. Craig pointed me to the three dams and scouting confirmed that once again, the stream bottom was the focus of moose movements. A beautiful morning midweek found Rob, Keith, and I hunkered down in vegetation on the edge of the upper pond, still in reasonable shape despite the dam having been abandoned years earlier.

If we had any doubts as to the ecological value of beaver ponds, that morning dispelled them quickly. As we sat there in silent observation, the forest around us was alive with bird song. After rain the previous day, it seemed that our avian neighbors were enjoying the day as much as we were. We heard or saw common birds like American Crows, Common Ravens, Black-capped Chickadees, Blue Jays, Northern Flicker, Hairy Woodpecker, and several Red-breasted Nuthatches caching seeds for winter. I was excited to hear the Ruby and Golden-crowned Kinglets, and the elusive Evening Grosbeak, a bird sadly in decline and not often spotted in our neck of the woods.

Then things turned really exciting as we were treated to some wildlife drama of the sort that happens only when you are sitting quietly enough to blend into the scenery. A Great Blue Heron flew in from the south and landed on a grassy hump. Naturally wary birds, this one gave us a long look to see if we represented a threat to his hunting plans. Satisfied that we were committed to quietude, the heron stalked into the water in search of prey. Craig later confirmed that this was the first sighting of the big heron on his pond.

Suddenly, in a rush of tiny wings, a flock of Green-winged and Blue-winged teal zipped into the pond. I was thrilled to see these little speedsters since they are early migrators, often heading south in August, and they favor small pockets of freshwater rather than the bays and ponds of Harpswell. The heron, however, was decidedly unhappy to have company on his pond, jumping onto a stump, flapping his huge wings and making deep croaking sounds to make his displeasure quite clear.

The tiny teal paid the heron little heed, popping up in the air and coming back down 30 feet away to continue feeding. This time of the year is meant for packing on the calories in anticipation of long flights to the south and cold weather to come, not the time to squabble with grumpy old herons! Quickly realizing that he would have to share his pond, the heron took flight in search of new territory, leaving the teal to swim around the pond for 30 minutes, bobbing up and down as dabbling ducks will do, in search of food and giving us a ringside seat on the show.  What a delight!

All of this was thanks to the beavers who labored long and hard to build the dam, creating a beautiful pond that still serves as an oasis for a myriad of creatures in a vast stand of mixed soft and hardwood forest. Yes, many trees were sacrificed to the beaver project but the return was new light in the forest, new soil in the stream bed to support vegetative growth, and vital new habitat for rearing young animals of all sorts. Craig and his wife Nancy are ardent conservationists who also thrill to the work of beavers on their property, knowing the long-term dividends to be reaped.

Conservation organizations like Trout Unlimited along with state fish and wildlife organizations around the continent are fully aware of the value that beavers can provide for restoring and protecting critical riverine and wetlands habitat. Numerous programs across the country are protecting beaver habitat, releasing beavers into the wild, and even building man-made “beaver dam analogues” to enhance habitat even without the presence of nature’s brilliant engineers. It will be a delight to have another opportunity in the near future to see beavers at work or to enjoy the fruits of their labor.

If you like Ed Robinson’s writing, check out his two Nature Notes books! Click here for more information.