In defense of long-toothed rodents

Published on Thu, Jul 25, 2002 by Tami Du Bow

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In defense of long-toothed rodents

By Tami Du Bow

One of the many benefits to living in Birch Bay Village is the proximity of a variety of marine and freshwater wildlife. This benefit does not come without some amount of compromise and can require creativity to keep everyone happy.

The beavers living in the Birch Bay Village beaver pond most likely consist of one family group, or “colony” that has established a dynasty in this location over time. Beavers are territorial animals. This means that the monogamous, mated pair remains in one defended area their entire lives, usually about 12 years.

The adult pair raises the young kits in their territory, and send them off at two years old to establish their own colonies. Thus, there are always young beavers in search of vacant territory. This reality makes the traditional method of beaver damage control, lethal or live-trapping, a short-lived solution because vacant territory will be reinhabited.

Being rodents, beaver’s teeth continually grow and must be filed down by frequent gnawing on wood. They cut trees for food and for use as building material in dams and lodges. Beavers are strict vegetarians with varied tastes that change seasonally. Although generalizations can be made about their vegetation preferences, there are always exceptions, and beavers have individual personalities and tastes.

In general, they cut down the most trees toward the fall to store food and shore up the dams for winter. During the winter in western Washington, where the water rarely freezes, beavers will continue to cut trees and to feed on what they have stored under the water in their caches near the lodge. In the spring and summer when greenery is available, they consume a lot of leaves, shoots, young trees, sword fern roots and lily pads.

What follows are suggestions for sharing beaver habitat in ways that minimally disturb them, while allowing people to live comfortably in their homes and gardens. There are no absolutes when dealing with wild animals, so be prepared to be creative and flexible, and perhaps try combinations of methods for the best results.

Traditional Fencing: There are many choices of fencing one can use to exclude beavers from an entire garden, or to protect individual plants.
In general, the fencing must be a minimum of three feet tall, with at least three inches buried in the ground and of a sturdy composition. Beavers are not climbers, but they are excellent diggers. The fence grid should be no larger than 6 x 8 inches.

Wooden fences can work, although they are vulnerable to beaver gnawing. Painting the wood with a sand/paint mixture (discussed further under repellents) could protect the wood. Wire fencing is the most likely to be successful. Chicken wire rarely works for long because it is so light-weight.
Keep in mind that an adult beaver weighs between 60 and 80 pounds, so the fence needs to withstand that pressure. Stream restoration workers in Whatcom County have found that 2 x 4 inch utility wire works best for protecting an individual tree or small group of trees. The wire cage is secured to the ground with bamboo stakes or rebar woven through the mesh. To protect large numbers of trees, restoration workers are using 6 x 6 inch field fencing which conforms more easily to uneven terrain. The larger grid also allows for wildlife other than beavers to pass through the barrier. A verity of fencing materials are available at CENEX, Hardware Sales and Home Depot.

Electric Fencing: One strand of electric fencing six inches off the ground between the pond and your yard can exclude beavers. Some recommend using two strands of wire, one at six, and another at 12 inches. Regular maintenance is required under the fence to keep foliage from making contact and shorting out the connection.

Repellents: Although some commercial herbivore repellents claim to work for beavers, they don’t work well enough to justify the cost. One repellent method showing promise, however, is a paint/sand mixture.

Exterior latex paint mixed with #30 sand (available from Pacific Concrete); 20 oz. sand: one gallon paint (approx. 1.25 lbs/gal) creates a textural repellent when applied to the bottom four feet of tree, that beavers don’t want to gnaw. The mixture should be made fresh for use and mixed constantly during application. Don’t be afraid to apply it rather thickly as exterior latex paint allows for transpiration through the wood. An advantage to this method is being able to match the paint color to the bark.

Plant choices: Beavers like some trees more than others. Unfortunately, this does not guarantee that they will not first cut something, and then decide they don’t like it. Some of their favorite trees are Willow, Cottonwood, Alder, Apple, Cherry, young Western red cedar, Black hawthorne, Birch and Big leaf maple. Among native vegetation they are significantly less likely to cut Sitka spruce, Douglas fir, Hemlock, Cascara, Elderberry, Ninebark, Twinberry, Vine maple and Indian plum. Scientific studies in other area of the country reported Beaked hazelnut, Canada honeysuckle, Balsam fir, Northern white cedar, American elm, Silver and Red maple, Prickly ash, Black gum, Water oak, Titi, and Silver bell as less preferred by beavers.
Feeding diversion: One strategy is to plant a large number of native rooted willows along the bank of the pond to divert the beavers, hopefully keeping them satiated enough not to venture into your yard. Rooted willows are a renewable food source for the beavers as the browsing stimulates rapid and vigorous regrowth. Other native shrubs that beavers will cut, but that rapidly resprout are Dogwood, Sitka alder and Spirea.

Flooding: Beavers can cause flooding by building dams and blocking culverts. There are flow devices that can be built to allow the beavers to continue their behavior, while controlling the water level. These require a hydraulic permit from Washington State Department of Fish and Wildlife and skilled installation.

For more information contact Tami DuBow at 733-3509 or tdubow@hotmail.com..
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