Beavers: Extraordinary Architects
Last October, I was both delighted and dismayed to discover the handiwork of beavers in a nearby wooded wetland, where the furry little engineers had constructed a barrier of aspen and birch branches and mud across a narrow culvert, damming the small stream and creating a lovely wetland in its place. It was beautiful and serene, as titmice and cedar waxwings flitted and twittered all around, and the autumn reflections of overhanging red maple, yellow birch, black cherry and hemlock danced in gentle ripples upon the surface of the newly-formed pond. On the one hand, I celebrated the creation of this new wetland as a gift of nature — wetlands provide critical habitat for fish, ducks, geese, turtles, amphibians, mink and countless other creatures, while regulating and recharging ground water supplies, reducing erosion, filtering out sediments, detoxifying pollutants and minimizing flooding downstream. And I celebrated the creativity, ingenuity and adaptability of the beavers themselves, whose architectural and construction skills are nothing short of phenomenal. But on the other hand, I also grieved, knowing that these particular beavers were likely doomed — for their wetland was in the midst of property where their activity would not be tolerated by the landowners and where human concerns over flooding upstream would take precedence. No other mammal has a greater ability to alter its environment than the beaver, except for humans. And rarely will humans tolerate the competition.
The North American beaver (Castor canadensis) is the largest member of the order Rodentia, named from the Latin “rodere,” which means “to gnaw.” Their scientific name refers to the beaver’s castor glands, which produce a special scent with which they demarcate their territory. And masters at gnawing they are! With chisel-like incisors and powerful jaws, beavers can easily cut down a five inch thick willow in less than three minutes merely by biting out chips in a deep groove around the trunk. Beavers especially seek out trees such as aspen, willow, birch and red maple, using them as preferred foods and to provide construction materials with which they create their dome-like home (the lodge) and their quiet-water habitat (via their dam). Once a tree is felled, beavers trim and cut the branches into pieces, and carry them to the lodge or dam site. Larger branches provide the dam’s scaffolding, which is reinforced and packed with smaller twigs, grasses and cattails, then caulked with mud. Dams may be six feet high or more, reaching 25 to 40 feet across. Their purpose is to create a still, safe, and relatively deep watery habitat in which the lodge may be built, winter food may be stored and young may be raised.
A pair of beavers typically mate for life, breed between December and February and bear 4 to 5 kits about four months later. While newborns can swim within a half an hour after birth, mama keeps them close and may carry them on her back as she swims. Although parents produce a new litter each spring, juveniles from the previous year remain with the family a second year, helping with housekeeping and the care of younger siblings. Most beaver colonies are thus families of 4-8 individuals, the two adults and their children from the previous two breeding seasons. Family members greet each other, groom each other, wrestle, dance and play along with caring for and maintaining their carefully constructed habitat. Most of these activities are rarely seen, however, because beavers are nocturnal and busiest at night. Upon reaching sexual maturity at 21 months of age, the young adults are sent away to disperse into new territories, build new dams and lodges and begin their own little families.
Lodges, like dams, are impressive. Most lodges consist of one or more compartments, with two underwater openings for exit and entry, which is especially important for escaping from predators such as dogs, coyotes or bear. Living quarters for the family are in a hollow near the top of the lodge, with woodchips on the floor to absorb moisture and a vent to admit fresh air. A cache of winter food is stockpiled nearby, usually cut branches poked into the muddy pond bottom and ready for the taking. When eaten, a branch is held like an ear of corn, and the outer cork, cambium and sweet inner bark are eagerly consumed, along with leaves, fruits, seeds and even roots.
As remarkable as they are, beavers were once valued only for their dense, insulating pelts, and relentless exploitation nearly led to their disappearance. Fortunately, by the 1940s, new appreciation of their ecological role and revised management strategies eventually led to their spectacular recovery. With recovery have come renewed beaver-human conflicts, and rarely do the beavers win. It doesn’t have to be this way. If human tolerance and innovative solutions are embraced, humane remedies can be found. One promising, non-lethal approach is the “beaver deceiver,” or beaver pond flexible leveler, which is a flow device which controls the height of water behind a beaver dam to prevent flooding upstream.
Becky Nystrom is a Professor of Biology at Jamestown Community College, a founding trustee and current board director of the CWC, and a longtime CWC supporter and volunteer. The Chautauqua Watershed Conservancy is a local not-for-profit organization dedicated to preserving and enhancing the water quality, scenic beauty and ecological health of the lakes, streams, wetlands and watersheds of the Chautauqua region. For more information, call 664-2166 or visit www.chautauquawatershed.org or facebook.com/chautauquawatershed.