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Living with Beavers

Management

Even in environments where beavers are appreciated and tolerated, their activities can become problematic if chewing and dam building damages property or causes flooding that threatens infrastructure such as buildings, roads and railways. There are several options for landowners to deal with beaver issues, including:

  • Preventing conflicts
  • Addressing existing problems, such as flood control
  • Live trapping and relocating beaver
  • Lethal control

Understanding that beavers fulfill an important role in the ecosystem by creating wetlands that provide multiple benefits to a variety of fish and wildlife as well as landowners, a beneficial approach is to beaver management is learning to co-exist with the beavers. The presence of beavers is often seen as a problem when, in fact, the beavers are causing no harm and may be providing important ecosystem benefits. To assess the beaver problem, it is important to consider if the beaver are really causing damage or creating hardship, and then determine the appropriate control action.

Preventing Conflicts

Protecting Plants and Trees

Beavers may fell a wide variety of trees, though they tend to cut fast-growing trees, such as poplar, willow, cottonwood and alder that have little commercial value. Although the felling of these trees may appear destructive, such culling often results in more, bushier growth next spring. For example, each willow stump may sprout three to four new stems, while other species regenerate from their roots.

In areas where the landowner or manager is interested in protecting trees from beavers, it is important to note that most, but not all, cutting occurs within 50 feet of the water. While beavers prefer certain tree species, they will cut trees that are most accessible, so it is a good idea to protect desired individual trees. It is beneficial to leave the trees that are already down, so the beavers are not driven to cut more.

Prevention

In areas where landowners and managers are interested in protecting key trees or stands, the following prevention methods are effective:

  • Individual large trees can be loosely wrapped with 3 foot high, galvanized welded wire fencing or hardware cloth, both of which can be painted to make them less noticeable. Welded wire fencing coated with green vinyl the helps the fencing blend in is also available.
  • Lengths of corrugated plastic drainpipe can be attached around the trunks of narrow-diameter trees. (Note: Dark-colored pipe can burn trunks in full sun; wider diameter pipe or pipe with holes in it may prevent overheating problems.)
  • Groups of trees and shrubs can be surrounded with 4-foot high barriers made of galvanized, welded wire field fencing or other sturdy material. Chicken wire is not an effective material as a beaver’s weight will pull down the fencing. Keep the bottom of the fence flush to the ground, or include an 18-inch wide skirt on the beaver side of the fence to prevent beavers from entering underneath.
Photo of aspen group with trunks fenced.

Multiple trees can be protected by small exclosure fencing.

drawing of tree trunk barrier

Barriers can be used to protect plants from beaver damage. All plants should be protected to at least 3 feetabove the ground. Figure courtesy of WDFW.

Repellents
Photo of tree-trunk painted with repellent.

Trees can be painted with abrasive paints and repellents. This method may require regular application.

Painting tree trunks with a sand and paint mix (2/3 cup masonry grade sand per quart of latex paint) has proven somewhat effect at protecting trees from beaver damage. The animals presumably don’t like the gritty texture. Commercial taste and odor repellents have provided some success, but are more labor intensive as they must be reapplied often, particularly in moist weather. Two repellents that have proven effective in some cases are Big Game Repellent® and Plantskydd®. For maximum effectiveness, these repellents should be applied at the first indication of beaver activity and re-applied a few times per year during dry weather. Repellents are not as effective as properly-installed fencing, but are an option in areas where fencing is not desired.

Flood Management

Removing or breaching dams is an immediate, but usually temporary, solution to flooding problems caused by beaver. In many cases beaver will rebuild the dam, sometimes as soon as overnight. It is often possible to control the pond level to prevent flooding and property damage using a flow device. Before starting any of the following treatments or activities, landowner approval must be obtained. In addition, as these activities typically require some work in wetlands or streams, permits may be required from various local, state, and federal agencies before work is started. Please refer to the Montana Stream Permitting Guide and contact Department of Natural Resource Conservation for assistance.

Flow Devices

Dam Management

Beavers create attractive and beneficial habitat by building dams, and often a series of dams, to pool water. When the damming activity creates nuisance flooding, we can still keep beaver and the high quality habitat but prevent damage from flooding by installing flow devices to regulate water levels at beaver ponds. Flow devices allow water to flow through a beaver dam and maintain a desired pond level, preventing flooding of adjacent roads, pastures, or structures. For flow device systems to work properly, you may need to have at least 3 feet of water in the pond area for the beaver to stay.

Barrier around a tree trunk

Example of a Castor Master TM flow device that controls the water level and prevents flooding while allowing the dam to stay intact. The dam in this picture has been notched for installation of the device and has not yet been repaired by beaver. Photo credit: Amy Chadwick

The Castor MasterTM, a design of Skip Lisle at Beaver Deceivers International, is an example of a highly effective device that controls water levels while allowing the dam to stay intact. The design includes a pipe extending through the beaver dam, with the pipe intake protected to prevent plugging by beaver. A flow device such as the Castor Master requires little maintenance (estimated 0. 5- 1. 0 hours/year), and with proper construction the effective life of the device is at least 10-20 years. Material, construction and installation costs range from about $900 to $2500 per flow device, depending on the location, structure size, number of sites at one location, and site characteristics. Other designs, such as the Clemson pond leveler, have proven effective in many situations. In general, flow devices pay for themselves within the first 1–2 years and are an affordable, long-term management solution.

Every site requires a specific design, developed based on beaver activity and likely response, site environmental controls, flood tolerance for protecting property, and proximity of other beaver activity. For sites with ongoing flooding issues, damming in irrigation ditches, and multiple dams we recommend a thorough site review to check project feasibility, develop a plan for beaver management, and define success criteria prior to any installation efforts.

For site evaluation and technical assistance, please refer to contacts on the Resources page. Each site is unique and requires evaluation and custom construction designs. Please see Living with Beavers 811 KB for more information.

Culvert Management

Beavers respond to the sound of flowing water through culverts by damming narrow channels and culverts, which impounds water against roadbeds and causing roads to flood or washout. Plugged culverts are difficult, time-consuming and expensive to repair, and road damaged caused by beavers is a costly problem. Trapping and dam removal is only a short-term solution that requires continual maintenance as beavers will re-colonize and rebuild. Installing a barrier to prevent dam construction is an effective, affordable, long-term solution to maintaining functioning culverts and roads.

A Beaver DeceiverTM is a flow device that protects culverts at roads or irrigation headgates and consists of two filters constructed of sturdy wire and wood posts with a pipe to connect the filters, which maintain water flow through the culvert, reduce the sound of flowing water, and prevent dam construction. This system is an effective solution to address the culvert plugging and provide the benefit of dramatically reducing maintenance costs. These structures are built to last at least 20 years with minimal maintenance. Cost savings provided by these structrues were documented in a 2006 study funded by the Virginia Department of Transportation, which compared the cost of flow device installation to traditional maintenance (culvert unplugging, dam removal, trapping) and found that every $1 spent on flow device installation saved $8 in maintenance costs. See Further Reading for more information.

Photo of another Beaver Deceiver.

Another Beaver DeceiverTM design for a larger stream with more flow fluctuation.

Photo of Beaver Deceiver.

Example of a Beaver Deceiver TM installed in an irrigation ditch to a protect culvert from damming and prevent associated flooding and road damage.

For all flow device systems, each site is unique and requires evaluation and custom construction designs. Please refer to Living with Beavers 811 KB or Technical Assistance for additional information on flow devices.

Live Trapping and Relocation

Photo of beaver dam.

Photo credit: Amy Chadwick

Beaver trapping tends to be an expensive and short term solution, as new beavers will relocate to the trapped area, often within 1-2 years. Beavers are classified as furbearers in Montana and you must have a license or damage permit to trap legally. If trapping is the only solution, please contact Montana Trapping Association for expert assistance. Additionally, many of the Montana Fish, Wildlife & Parks offices also maintain a list of trappers who can assist with live trapping efforts and can arrange trapping.

Relocating beavers to a new site requires cooperation between adjacent landowners and local wildlife officials, particularly if there are not already beavers present at the new site. Relocation of live animals may require development of an Environmental Assessment, which will provide a cooperative evaluation of existing habitat quality and potential adverse beaver activity. It should be noted that beaver will cut a large number of trees for dam building for the first year or two after relocation. It may be helpful to provide beavers with a truck load of aspen or other trees to use as building material at or near the release site. It is best to relocate beavers during from late July to September, within their principal dam-building period but early enough to allow them to set up their winter lodging and food cache. Trapping and relocation should be avoided in May to June, when baby kits are still in the den and would starve if the adults are removed. For effective live-trapping and relocation the whole family unit should be trapped and moved together