If you have ever walked the Lake Nevin Loop, chances are you have walked across the boardwalk that spans the lake’s southern tip, leading to Little Elina. Built in the 2000s, the boardwalk is now the perfect viewing platform for one of the largest (about 180 feet) publicly accessible beaver dams known in the southeastern United States.
This beaver family’s proximity is an opportunity for visitors to see beaver structures up close, for Bernheim staff to observe the complex’s development, and for volunteers to do important work to improve beaver-human relationships in the arboretum (see the work done by our Beaver Brigade volunteer group).
It also has led to many great questions from visitors and volunteers. Questions like: How many beavers live in this beaver complex? What is the beaver’s group structure? Does this group have a lodge, and where is it?
Based on our observations and beaver biology, here is what we know about the Lake Nevin Beavers, and some of our best guesses about their story and family structure.
Arrival: The Lake Nevin beaver pair
In the spring of 2021, Bernheim’s decades-long policy to trap and remove beavers from the arboretum was upended, and the final traps were removed. That spring, like every spring, young 1-3-year-old beavers across the continent were coming of age and leaving the safety of their parents’ compound. They’ll wander miles in search of a life mate and their own stretch of waterway, braving both predation on land and fierce competition for territory. From some distance that we will never know, one lucky young beaver pair wandered their way into Lake Nevin.
From the beaver’s perspective, one can imagine swimming upon the Lake Nevin bridge elevated over the slow-moving, shallow water perfect for damming. What looks to us like support beams looked to them like the perfect built-in structural support for a dam: a once-in-a-lifetime opportunity. A quick recon would reveal healthy forests on both upstream banks, which promised to keep them in woody forage for many years to come. With little more to ask for, these opportunistic beavers immediately began construction on the impressive 180 ft. dam that spans the bridge today.
Building: The early years
The beaver dam is the foundation from which a beaver pair builds their life. To beavers, water equals safety. On land, they are capable but slow: easy prey for coyotes, foxes, and even humans. In the water, they are prodigious acrobats, unreachable to most predators. Therefore, when a beaver pair finds a place they want to settle, the dam is first on their to-do list.
Through the summer of 2021, they spent months working: gnawing down trees, driving sticks into the creek bed, weaving twigs through the framework, and dredging up pawsful of mud and leaves to fill the gaps. By the end of the fall, their tenacity yielded success: they were holding back water. As the water level rose, their area of safety and forage widened, and they were working toward the water depth they needed to build a freestanding lodge with underwater entrances.
But their work was far from over. As they built their dam, summer yielded to fall and approached winter, a time where herbaceous forage disappears. Sensing this pressure with the shortening daylight, the pair pushed hard to collect woody forage and store it underwater where the cold would keep it through the winter. They did not have enough time to construct a full-size lodge, so they had to make do with their small, hastily dug, temporary den.
In the spring of 2022, their first litter of 3-4 kits would arrive, and life would somehow get even busier. The parents must feed their babies for the first 3 months, both through nursing and collecting forage. They groom and guard their newborns, clean up the den’s floor and bedding, all the while still collecting forage for themselves . After a couple months, the parents must drag their fearful kits down the watery entrance of the den -whose safety they have never left- and force them to begin their slow transition to adulthood. As the parents continue to build up their compound, they must also now carry the weight of their kits clinging fearfully to their fur. Eventually, the kits will detach and begin attempting to copy their parents’ building behavior, but they are mainly unsuccessful and completely unhelpful for the first year of their lives.
Despite all this pressure, the Lake Nevin beaver pair managed to survive, further build up their dam, build a bank lodge on the east side of the lake, forage for the next winter, and likely begin dredging up a system of canals along the bottom of their pond. Fall gave way to winter again, and the young family bunked down for the winter in their new lodge, resting from the summer and fall’s work.
The next few years were easier. The first year’s kits were now grown up, capable of helping build and improve the family’s structures and tend to the new litter of kits. The year after that, both the first and second year kits would be around to help too. In 2023, the Lake Nevin beaver family improved their dam and built another bank lodge across the lake from the first. By 2025 the dam was built up to its current impressive size and the family had built a roomy standalone lodge, which is upstream of the dam, tucked away out of sight from any of Bernheim’s trails.
Maintenance: A healthy family
Beaver family members are strongly bonded to each other through play, mutual grooming, and sharing warmth and space in the lodge through the winter. They rely on each other to survive, and will often die if separated from their family. It is a cooperative, communal, and hierarchical system with the original breeding pair at the core.
At any one time, the family consists of the original breeding pair and 1-3 years’ worth of kits, who stay behind to help the parents raise the newborns as they grow stronger in preparation for their own dispersal. Beaver compounds are occupied by only one family at a time, but that family can grow quite large, sometimes up to about 14 members. Because individual beavers are extremely difficult to differentiate visually (beavers rely much more heavily on scent than sight), we do not know how many family members live in the Lake Nevin beaver pond. However, considering how large and built-out the colony is, it is likely they are a sizable family, maybe around 10 members at any given time.
As with human developments, the more developed the family, the more structures there are, and the more that must be maintained. The beaver’s work never stops, and the parents spend their lives constantly repairing dams, and fortifying lodges, among many other chores. Bernheim staff were lucky enough to capture some of this maintenance activity after heavy June rains burst through a section of the Lake Nevin beaver family’s dam. Over the course of July, trail cameras captured the beavers building the section back out to a solid wall, integrating sticks, leaves, and mud to create a sturdy new seal.
Moving on: The future
One day, the Lake Nevin beaver family might have to move on. Forage, disease, and major dam blow outs can all drive beaver families to relocate. For now, we have the unique opportunity to observe, learn from, and appreciate these unique and industrious creatures from up close. The next time you are visiting Bernheim, consider coming down to the Lake Nevin boardwalk to take advantage of the opportunity to check out the dam for yourself!
Feature image by 2022 Environmental Artist in Residence Carla Rhodes.
Source: Could beavers be the secret to winning the fight against wildfires?, nationalgeographic.com
