Authored by: Dr. Thomas E. Eveland, Ecology Consultant
The beaver means different things to different people. Only a few centuries ago, some Native Americans considered the beaver "big medicine," a spiritual animal to be treated with great respect and reverence. The early settlers on the other hand saw the beaver as "living gold," an animal with a high-priced fur that could bring a successful trapper considerable wealth and prestige. Today, our perceptual images of beavers are quite different than those of our forebears. Though we no longer worship beavers for the "big medicine" or compare the value of their pelts with that of gold, we do have unique cultural perceptions of beavers. For instance, a municipal road supervisor might see the beaver as a nuisance, constantly making life miserable by flooding roads and clogging drainage culverts. Ecologists and nature lovers, however, see the beaver as an indispensable and integral component of nature's web of life.
The truth of the matter is simply that, at times, beavers can be either or both, a positive or negative influence on our lifestyles. Learning to live with beavers, until recently, has been difficult for many people, municipalities, and state wildlife agencies. Correcting beaver problems meant eliminating the beavers. The drawback to this was simply that the positive influences of beavers were also removed. Thanks to modern technology and a new understanding of this unique species, it is now possible to diminish, or even eliminate, beaver problems without removing or destroying the beaver and hence prevent the loss of its benefits as well.
The beaver is classified as a rodent because of its unique dentition, but is more closely related to the squirrels and marmots of Rodentia than it is to the rats and mice. Having a life span in the wild of approximately 12 years, adult beavers can attain weights exceeding 50 pounds.
Besides being the largest member of its family on the continent, the beaver has many specialized features that make it unique among the animal world. Some of these specialized features are easily recognizable and are key ingredients to the beaver's success. Its tail, teeth and feet are just for gnawing. The outer front layer of the large front incisors are made of a bright orange and very hard enamel. The rear side of these teeth are made of a softer dentine. Hence, as the beaver gnaws, the softer rear portion of its incisor teeth wears down faster than the enamel fronts. This makes the teeth self-sharpening and gives them a chisel-like shape.
Another key feature of the beaver is its feet. The front paws are very flexible and used for digging and carrying mud, sticks, and other debris back to the lodge or dam. The hind feet are fully webbed and may measure six to seven inches long. It uses these feet for swimming and standing. Possibly the most outstanding feature of the animal, though is its unique tail. Attaining 15 inches or more in length and six to seven inches in width, the tail is used as a prop while standing and a rudder while swimming. At close inspections, the tail shows layers of scales that are laid in a pattern resembling those of a snake, or in the seeds of a pine cone.
Although these features make the beaver very unique and easily recognizable, it is the lifestyle of the beaver itself that makes it a controversial species. Beavers are one of those very rare species besides humans that substantially alter their environment for their benefit. When a family of beavers alters an area the general vicinity undergoes a radical change. First, beavers build dams, because the ponding of water will provide a safe haven for the beaver to carry out other important duties without the threat of attack from predators. After completing the building of a dam, a beaver may build a lodge, possibly other upstream dams, and a series of channels developed for floating branches and logs into the main pond. The area a beaver claims for its own can be large and extensive and may change the general character of the area for decades.
In order to build lodges and dams and also keep its perpetually growing, yet chisel sharp front teeth worn down, beavers continually gnaw on and cut down trees. In spring, beavers may cut trees for food and for materials to repair damages to lodges and dams caused by winter ice. Summer is a period of little tree cutting as the beaver feeds more on fresh grasses, tubers, and young saplings. Autumn, however, is a period of extensive logging by beavers.
Since beavers do not hibernate, they must have available food for the winter months. And since their pond may freeze over for several months during the winter, they will not be able to cut new trees. Hence, autumn is a period of extensive cutting for beavers as they can chop limbs into manageable pieces into their main pond, and store them underwater.
During the winter freeze, the beaver can swim from its lodge under the ice to the winter food cache, grab a choice limb and swim back to the lodge where it can eat in peace. This can all be done under the frozen surface of the pond without exposing itself to the severe winter winds and predators. If the beaver does not cut and store enough branches in autumn and winter holds its icy grip on the land for an extended period, the beavers will starve in their own lodges.
Earlier it was stated that beavers may have both positive and negative impacts on our lives. So before going into discussion regarding problem solving, let's take a moment to outline both the good and the bad.
Beavers can significantly alter a fishery. However, whether that alteration is good or bad depends largely on what species of fish is being discussed. It can also vary from one part of the country to another.
The state of Wyoming, for instance, joined forces with the Bureau of Land Management (BLM) to restock beavers into many mountainous areas of the state. One motivation behind this plan was the enhancement of the brook trout fishery. Fisheries research in Wyoming discovered that beaver ponds were ideal brook trout habitat and that this species grew faster and bigger in beaver ponds than in streams. Similar studies in Wisconsin discovered that new beaver ponds only a few years old were beneficial to brook trout but older beaver ponds were not necessarily favorable brook trout habitat.
In Wyoming, beaver ponds did not affect brown trout but did negatively effect rainbow trout because this species has migratory habitats that were largely restricted by the dams. Also, some southern states have noted a direct benefit to smallmouth bass populations in areas of high beaver concentrations.
Brook trout and beavers have coexisted throughout much of North America for thousands of years. It is highly doubtful that beaver activities would have a disastrous influence on brook trout populations since the two species have lived together in relative harmony for so long. On the other hand, introduced species of fish that have not closely evolved with beaver may or may not benefit depending upon the special needs of that particular fish species.
First and foremost, it needs to be stated that beavers do not create problems in natural or wilderness areas. It is only when they come into contact with people, or people "things," that conflicts sometimes occur. And since beavers are going to do what instinct tells them to do, the emphasis of problem solving is placed solely on the human participant.
Beaver problems, like most wildlife-related problems, are more often than not, actually people problems. Many people enjoy beavers and are very appreciative and respectful of these animals. Yet other people simply don't want beavers building dams or cutting trees on their property. An unwillingness to accept natural changes brought on by beavers or misconceptions of beaver behavior and habits are generally the cause of why some people want beavers removed from their property. Education is usually the key factor to correcting these problems.
Occasionally, legitimate beaver problems do arise. A property owner loses an expensive ornamental planting to a beaver, a township supervisor reports a municipal roadway is being flooded by a beaver dam, or a utility lineman is called out in the middle of the night to get a freshly gnawed tree off electrical wires. One by one, let's take a look at what can be done to either prevent or correct beaver problems.
If you live in an area that has beavers, own property with trees, and are located near water, there is always the chance that some of your trees will be selected by beavers for cutting. After all, that is what beavers do to survive. However, some species of trees are preferred over others. Here is a preferred species list:
If your property has any of these species and is directly adjacent to an area populated with beavers, chances are good that some cutting will occur. Most cutting can be expected in early spring or mid to late autumn. If certain individual trees have historical significance, are expensive ornamentals, or have some other specific importance, you can protect them.
The following information was taken from a paper distributed by The Beaver Defenders of Newfield, NJ (contact information on reference page). The Beaver Defenders experimented with several types of tree protectors and came up with the following recommendations. Individual trees can be spared from beaver gnawing by placing wire cylinders around them (see graphic #1). Cylinder cages should be made of heavy wire fencing 2 inches x 4 inches in size and 3 feet in height. The should be well anchored to the ground to prevent beavers from crawling under.
The Beaver Defenders also suggest that the space between the tree and the wire be no less than 6 inches and preferably 12 inches. Also, by cutting the horizontal wires at one end and next to a vertical wire, and then bending the horizontal wire into a hook, these cages can be easily removed for use on another tree. Obviously, the idea to this heavy wire cylinder is simply to keep the beaver from getting to the tee.
For instance, in a park setting, a three foot high brick or stone structure could be built to serve the same purpose as well as being aesthetically pleasing by acting as a bench. These devices can stop an already existing problem or prevent one from occurring.
When beavers travel along a watercourse, they are seeking an area that is easily dammed and will provide an adequately sized pond. Such areas that appear to be ideal for this venture are culvert and drain pipes. Though the semi-clogged pipe may not be a problem in itself, the resulting backed-up water may flood the road 50 to 100 yards in either direction. In many regions of the country, municipal road supervisors and state workers waste thousands of dollars in taxpayer monies by spending time cleaning these pipes. And in all cases, the pipes are reclogged by either the same beaver or new ones within a short time. The best way of dealing with this problem is by installing a device known as a "beaver baffler," several of which are on the market today. The general purpose of such a device is simply to render a culvert or drain pipe incapable of being clogged by a beaver. This is accomplished by installing a wire cage-like device on the upstream side. Such devices have proven extremely successful in a variety of ways:
Basically, a baffler is a 15 foot to 30 foot long heavy wire cylinder that is attached to the upstream side of the pipe. Another cylinder of heavy wire is placed around the first cylinder leaving a space of at least six inches between the two. Both cylinders should be well anchored to the bottom of the stream and firmly attached to the pipe entrance. Also, a screen or wire cover needs to be placed over the upstream entrance of the cylinders and over the exit hole on the opposite side of the road. These prevent animals from entering and clogging the interior under the road itself (see graphic #2).
Beaver bafflers, if properly installed, have been proven to be nearly 100 percent successful. Neil Thurber of DCP Consulting, Inc. has developed an entire business around the development and installation of the Beaver Stop device (contact information on reference page). He regularly installs beaver damage control devices for municipalities and various resource-based industries throughout Canada. One firm estimated it saved almost $40,000 in the prevention of road maintenance and repairs with just 11 of Thurber's Beaver Stops.
Beaver dams are excellent flood control structures. They impound water and release it at an controlled rate. But beaver dams create beaver ponds. And sometimes these ponds can become small lakes inundating many acres. As a result, beaver dams sometimes backup water to the extent of flooding crop fields, pastures, roads, and in a few isolated cases even basements. Though rare, severe flooding of critical or important land areas does occur.
Often the landowners would be willing to leave the beavers and their dams intact if the size of the pond were reduced to control the amount of water being backed up. Experimental devices have been used for almost 30 years to control water levels behind beaver dams. And of all the experiments attempted, virtually all of them have consisted of placing some kind of draining structure through the dam itself. Many have proven successful, but some have not.
After reviewing a number of these designs, it appears that there is a formula for success. It simply involves combining a little engineering with the understanding of beaver behavior. One does not need an engineering degree to figure out that a drain is needed to draw down the water level of a beaver dam. A PVC or other pipe can be driven through a dam with a backhoe, sledgehammer, or some other power device. And, a hand calculator and a bit of mathematics can provide the necessary information relevant to the volume of water removed per size of pipe used. But the key to success is knowing how to install these drains so they are not immediately clogged by the beavers as soon as the workers leave the scene.
When a natural leak occurs in a dam the beavers respond immediately to repair the damage. Natural leaks often occur as a result of ice or high water damage. Beavers must respond immediately, otherwise the declining water level may eventually leave them high and dry, totally exposed to predators. When such a leak occurs, they are stimulated into action by the feel, the sound and the sight of running water. If the device is placed in such a way as to eliminate these stimuli, there is an excellent chance it will succeed. If any one of these stimulants exist after installation, the beaver will probably clog the hole with debris.
Overcoming these points is largely a matter of common sense. Just knowing what stimulates a beaver into action is the biggest part of the job. Proper installation to avoid these stimulants can be accomplished simply by looking at the world through the mind of a beaver.
The sight stimulant can be overcome simply can be overcome simply by keeping the entrance hole of the pipe far enough above the dam not to be noticed. The sound stimulant can be overcome by making sure no gurgling noises or other sounds associated with running water exist after installation. And the feel stimulant can be removed by using a pipe that is some way perforated so that all the water is not drawn through one end causing a current easily felt by a swimming beaver. The diagrams on graphic #3 are examples of homemade devices that have proven successful in most situations.
There are professionals who design and install devices that will control water levels on the back side of dams. Neil Thurber of DCP Consulting, Inc. clearly outlines the cost of his Beaver Stop devices and their success rates in a catalog that can be obtained by writing to the address on the reference page. The general purpose behind installing these water control pipes is to permit the beavers to carry on with everyday life activities without backing up water into a particular property that may prove harmful. And, it may be the only way of controlling property flooding in some situations. To break the dam may mean only temporary relief since the break will be quickly repaired by the beavers. And removing the beavers may be impractical in some situations if the area in question has a sizeable population.
When a water regulating device is placed in a dam, two things happen with the beavers. First, if all the stimulants have been removed and the water level is not drastically lowered, the beavers will not be affected. They will probably conduct business as usual. However, if water levels are reduced to the extent of exposing the beavers and their lodge entrance to predators, they will probably move to a new location. This could be better or worse depending on where the new dam is actually built. It is better to work with the existing dam so that both beavers and people can coexist together. When that is achieved, the problem is truly solved.
We do not have the technology to either correct or prevent most of the problems created when beavers and people collide. It is simply a matter of understanding the beaver, the problem, and the methods used to change a bad situation into a good one. When this knowledge is then applied the outcome can be very rewarding.
To site a case in point let's take a brief look at Gatineau Park a large lake-strewn area encompassing over 80,000 acres in Quebec with a high population of beavers.
Gatineau had a serious beaver problem which began in the early 1960s. Road flooding and drain pipe blockage were common and accounted for approximately 60 percent of all beaver-related complaints. And for nearly 20 years the park managers tried to correct these problems through dam breaking and trapping. In 1981, the park hired a contractor to deal with the unsolved beaver complaints. Realizing the quick-fix method was not solving the problems over the long-run, they wanted to try new and innovative techniques. First, they began experimenting with various pipes through the dams themselves to regulate the water levels. Later, they experimented with other techniques at road culverts. When all was said and done, their success was amazing. From 1980 to 1985 they recorded an increase of 15 percent in the parks's beaver population. Yet, with the installation of the experimental devices, the number of flooding problems was reduced by more than 75 percent.
In 1980, only 5 percent of the entire park was under long-term management. By 1989, over 80 percent of the park was being managed for long-term problem prevention. At one site in the early 1980s more than 80 interactions were recorded for a single year. Yet only one year later, after the installation of a drain and without removal of the beavers, the interactions had dropped only to four or five. Rather than call this a form of wildlife management, the park's employees deemed it "natural resource management," a more appropriate namesake. Beside producing an almost total reduction in beaver-related problems, the park's attempt at natural resource management produced other results.
For example, with no controls on the park's beavers, the estimated total population that would be reached in the near future caused some concerns. However, the following outcome was quite different than expected.
The park's beavers stabilized at only 60 percent of the estimated figure. Apparently, this self regulation was caused by the following:
So, with a progressive program of beaver problem control utilizing technology and the philosophy of natural resource management and combining this with the self-regulating abilities of the beaver itself, Gatineau Park's conflicts between beaver and man have been reduced to near zero.
Sometimes when a beaver/human conflict arises, the first proposed solution comes in the form of a suggestion -- why not live trap the beavers and take them somewhere else? Though this may be feasible in some cases, it is not a reliable solution in the vast majority of beaver/human conflicts. Here's why:
These are just some of the problems with live trapping and moving beavers. Also, it may be possible to live trap and move beavers successfully only to have others move into the problem site shortly after their removal.
In some rare cases, however, the live trapping and transfer of beavers is a viable option and possibly the only one. In order to successfully complete such a project, it is important to follow a specific list of guidelines. Once it has been concluded that the animals in question will be live trapped and moved, the following steps are recommended:
If this seems like a considerable amount of effort to go through, it is. Live trapping and moving a wild animal can be time consuming and difficult. And, if not properly done, live trapping can kill the animals in question. However, there may be a few positive aspects to such an undertaking that may make it easier.
For example, if it's a first time problem it may be possible that there is only one beaver. When a beaver is two years old it is booted out of the family group and may travel extensively until it locates a new home site. This would probably be in late spring through mid summer. If this is the case, then the individual beaver can be live trapped and immediately moved to another area a long distance away. The beaver itself is relatively easy to trap and transport. The can be easily drawn to a trap with the use of store-bought beaver scent and, once caught, the are fairly docile, do not need to be drugged, an will travel quietly inside the trap to a release site.
One of the biggest problems with live trapping and transferring beaver is doing it too late in the fall. Most beaver problems occur in the autumn months when the beavers are cutting trees to build up their food stocks in preparation for the upcoming winter. As such, many problem beavers are live trapped and moved in September, October, and November. The property owners feel good because the problem has been solved and the beavers are back in the wilderness where they belong. And the parties involved with the live trapping and transfer feel like they have done their part to help both beavers and people. In almost all cases, however, beaver moved to a new area after September never survive the upcoming winter. Here's why :
Beavers undergo a very active period in autumn. "Busy as a beaver" really does apply at this time. The lodge and dam have to be reinforced to withstand the winter storms, high water and ice. A sizeable food stockpile must be built in the middle of the pond. And, the beaver itself needs to fatten up for the winter. This is why the beaver is so active in autumn.
Live trapping and moving beavers during autumn means that they will have to reestablish everything in a completely new area. A new dam and lodge will have to be built, trees cut and food stockpiled for winter. And, this needs to be done before the first big freeze. It is simply too much for the beaver to do in such a short time. Often the dam and a liveable lodge will be completed, but not enough food will be stockpiled in the pond. As a result, sometime during the winter the beaver will run out of food. With the pond iced over, the beaver, unnoticed by human eyes, will quietly starve inside its lodge.
Under no circumstances should beavers be live trapped and transferred after mid September. However, they can be live trapped in autumn and held in captivity for the winter to be released into the wild the following spring. This has proven successful in some situations.
A case in point occurred on the campus of Iowa State University. Several beavers had moved onto the campus and were cutting both historical and ornamental trees. The whole family was live trapped in October and November but not released into the wild until the following spring. The family was held in a university facility very successfully for the winter. If the facility does exist, holding beavers in captivity is a fairly easy thing to do.
During the winter, the entire family of beavers naturally spends several months all living within the confines of one lodge. As such, a whole family can be held in small quarters for long periods of time with no ill effects. Also being vegetarians, beavers need only a modest supply of tree limbs, vegetables, and other plants to sustain them.
Wildlife 2000, a Colorado-based organization, may be the most progressive group involved with live trapping and relocation of beavers. They also have considerable experience with holding beavers for long periods. The Beaver Defenders and Friends of Beaversprite are two other organizations with information on these subjects (contact information listed on reference page).
Though live trapping and relocating beavers is an option to solving a problem, there may be considerable time, effort, and expertise involved to make it a successful endeavor. It is suggested that it only be done in situations that have no other alternatives. Also, it should not be attempted until all aspects of the option are thoroughly investigated and well planned to guarantee success.
Special Note: No corrective measures should ever be undertaken without first contacting the necessary authorities. Many states have laws that prohibit the disturbance of stream banks and stream bottoms without necessary state permits. Also, many state wildlife agencies prohibit the disturbance of beaver dams, lodges and the animals themselves by unauthorized individuals. Make sure all the necessary people have been contacted well in advance of any preventative or corrective beaver-related projects.
Beavers were either totally wiped out or greatly reduced in numbers throughout most of the lower 48 states by the turn of the e 20th Century. And for the first half of this century their populations remained low throughout much of their North American range. It has only been within the past few decades that beavers have begun to increase in number and have reclaimed much of their native territories. As such, many people are encountering beavers in areas where the species has not built dams, raised young, cut trees, and altered the local habitat for a hundred years or more. In some cases, property owners welcome this unique animal and enjoy its benefits. Others, who often don't understand the beaver, are unwilling to accept the changes brought about by this species.
Education programs can remove much of the human ignorance that surrounds the beaver. When people are made aware of both the good and bad virtues of the beaver, many opt to leave the species in peace. But, in those circumstances where active measures are necessary to either correct a beaver problem, or better yet, to prevent one, the technology does exist to promote a reasonable and successful outcome for both beavers and humans.
The Beaver Defenders
Unexpected Wildlife Refuge, Inc.
Box 765
Newfield, NJ 08344
(609) 697-3541DCP Consulting Ltd.
Beaver Stop Division
3219 Coleman Road NW
Calgary, Alberta T2L 1G6
Canada
(800) 565-1152
http://www.nucleus.com/~beavstopBeavers: Wetlands & Wildlife
146 Van Dyke Road
Dolgeville, NY 13329
(518) 568-2077
http://www.telenet.net/users/beaversWildlife 2000
P.O. Box 6428
Denver, CO 80206
(303) 333-8294
Maurice Burton, 1972, The World Encyclopedia of Animals, Funk and Wagnall, New York.
Leslie Ebbs, Spring 1989, "Leave it to Beaver," Nature, Canada, pp. 4-5.
Robert H. Giles, 1971, Wildlife Management Techniques, Third Edition: Revised, The Wildlife Society, Washington, D.C.
Doug Hand, November 1984, "Beavers Are Back -- And Busy," Smithsonian, Vol. 15, No. 8, pp. 162-170.
Lewis H. Morgan, 1986, The American Beaver, Dover Publications, New York.
Robert J. Naiman, Carol A. Johnston, and James C. Kelly, 1988, "Alterations of North American Streams by Beaver," BioScience, Vol. 38, No. 11, pp. 753-761.
Leonard Lee Rue III, 1964, The World of the Beaver, J.B. Lippincott Company, New York.
Lars Wilsson, 1986, My Beaver colony, Doubleday and Company, New York.
