NCSU Wildlife Damage Notes

Wildlife Damage Management


Beavers

Just 50 years ago, beavers were rare in North Carolina. However, because of restocking efforts between 1939 and 1956 and because beavers have naturally expanded their range across much of the state, this is no longer the case. Today many owners and managers of bottomland tracts in North Carolina report the flooding of roads, timberland, and other property because of beaver dams. This fact sheet explains how to protect against beaver damage and to reduce beaver populations when necessary.
Although economic losses of up to $1 million have reportedly been caused by beavers in some regions of the state, not everyone regrets the return of the beaver. Many people, particularly duck hunters, trappers, and nature enthusiasts, enjoy the benefits of beaver ponds, as they provide excellent habitat for many kinds of wildlife. Beaver ponds also improve the water quality of our rivers and bays by slowing the drainage of the land, allowing sediment to settle out of turbid waters.

Even when beavers finally move on or are removed, their drained ponds continue to provide important benefits. The exposed mud flats provide fertile soils for future agricultural operations, or they grow up with lush vegetation to produce diverse wildlife habitats. These and other benefits of beavers need to be kept in mind when control measures are considered.

When beaver activity becomes significant enough to be called beaver damage, several options are available for managing the problem, including exclosures, electric fencing, water-level control structures, and the removal of all or part of the local population of beavers by trapping, shooting, or both. Several other control methods are largely ineffective and should not be considered. Relocation of "problem" beavers is not recommended because the cost is high, many transplanted individuals die, and moving beavers to other areas does not solve the problem but simply transfers it to someone else. Repellents to protect crops and landscape shrubs and trees have not proven effective, and fumigation to kill beavers in their dens is not approved in North Carolina. Therefore, relocation and the use of repellents and fumigants are not discussed further. When considering which option or combination of options to use, be sure to take into account all aspects of the problem and the possible solutions, including the location and severity of the problem and the long- term economic and ecological effects of the proposed control measures.

In keeping with the principles of integrated pest management (IPM), this fact sheet presents economical and humane ways to reduce or eliminate beaver damage. Measures for protecting trees, shrubs and gardens from damage; for protecting culverts and standpipes from plugging; and for removing local populations are presented. For any IPM system to be successful, it is important to inspect the property regularly and take prompt action to prevent renewed problems.

Legal Status of the Beaver

Responding to the increased need for the year- round control of beaver problems, the North Carolina General Assembly changed the legal status of beavers and liberalized control options in 1993.

On April 26, 1993, the North Carolina Legislature established seasons for taking beavers and made it legal to take depredating beavers without obtaining a permit from the North Carolina Wildlife Resources Commission (NCWRC). This law applies to all North Carolina counties except Buncombe, Madison, McDowell, and Yancey. The law opens the season for taking beavers with firearms year round as long as permission is obtained from the owner or lessee of the land. Beaver parts can be sold outside of the regular trapping season only if a depredation permit has first been obtained from the NCWRC. Snares and properly set Conibear 330 and foothold traps are legal trapping aids. Snares and traps must be checked at least daily.

Any landowner or lessee whose property has been damaged or destroyed by beavers may take the beavers at any time on that property using any lawful method, and he or she may obtain assistance from other persons in taking the depredating beavers by simply giving those persons permission to remove beavers. If trappers aiding the landowner do not sell beaver parts, they are not required to have a trapping license.

Protecting Landscapes and Crops

Property can often be protected against beaver damage without removing the beaver population. A fence may be installed to protect individual trees or plants in lawns or gardens. To discourage beavers, the fence should be at least 3 feet high and constructed of 1/2- inch- mesh hardware cloth or 2- by- 4- inch welded wire. Install the fence so that it is 8 to 10 inches from the plant and completely surrounds it. The fence can be supported by burying the bottom 3 or 4 inches in the ground and driving metal rods into the ground inside the fence.

Beavers sometimes cause considerable damage to agricultural crops such as corn, peanuts, and soybeans, and they may also damage orchards, vineyards, and commercial nurseries. The loss of these plants may be avoided in many instances by not locating valuable agricultural and nursery operations close to large water sources or areas of current or past beaver activity.

Beaver damage can be minimized or prevented by installing an electric polytape such as the Gallagher Turbo brand. One or two strands of 1/2- inch- wide electric polytape, raised 4 inches off the ground, is sufficient to protect even the largest areas (Figure 1). The polytape should be run on nonconductive or insulated posts. On flat ground, posts can be spaced 20 to 30 feet apart, whereas in more rolling areas a 6- to 10- foot spacing may be necessary to maintain the 4- inch height. A 2- to 4- foot- wide strip of bare ground should be maintained under the tape by applying a knock- down herbicide two or three times per year, possibly in combination with a preemergent herbicide and mowing.

Beaver Figure 1
Figure 1. Electric polytape fence used to protect a vineyard.

In areas of up to 10 acres, the electric polytape can be charged with 12- volt batteries. A combination of a solar battery charger and a 12- volt battery may be necessary to protect larger areas successfully. One person working alone can easily install polytape at a rate of 1,200 feet per hour. The cost of materials for this system averages $4.25 per foot, or approximately $62 to $65 per acre, depending on the supplier.

Preventing Flooding of Roads and Protecting Pond Drains

Beavers instinctively try to block flowing water by plugging culverts and pond drains and by rebuilding dams that have been damaged or destroyed. Modifying their behavior so that the landowner retains control of the water flow and resulting pond levels remains a challenge.

Fencing to Protect Culverts

Protecting a culvert from blockage by beavers can be difficult and time consuming; however, fencing can be effective. Success in using fences depends on (1) the number of beavers attempting to block the culvert, (2) the size and topography of the upstream drainage area, (3) the minimum and maximum flow of the stream, (4) the amount and type of materials available locally to block the culvert, and (5) the persistence and patience of the people who regularly clear away debris to maintain a free flow through the fence.

The simplest way to protect a road culvert is to construct a fence upstream from the road (Figure 2). The beavers will then construct their dam against this fence instead of at the entrance to the culvert. Installing several 6- inch- diameter plastic (PVC) rigid leach- field drain pipes through the fence will also aid in controlling water levels. The height of the beaver dam at the fence must be reduced and debris must be removed from the area around the leach- field pipes periodically. During periods of high water flow, the flow rate may exceed the capacity of the PVC pipes and may temporarily overflow the top of the beaver dam and the fence.

Figure 2
Figure 2. Fencing installed to protect a culvert from blockage.

The second type of culvert excluder, called a baffler, is also intended to keep beavers from blocking culvert sites. Bafflers are constructed by rolling various sizes and lengths of wire mesh into cylinders that are then placed in the culvert, allowing water to continue to flow into the culvert even in the presence of debris. The baffler may be as simple as a single piece of concrete reinforcing wire rolled into an open, 3- foot- diameter cylinder or a combination of intermeshed rolled wire and solid slotted PVC pipe glued or epoxyed together.

Researchers at Clemson University have developed a combination baffler and water control device called the "Clemson Beaver Pond Leveller" (Figure 3). It has proven effective in many situations where damage has occurred and gives landowners a good alternative to removing local populations. The pond leveller has a definite advantage over other drain systems: instead of having to remove it to allow water levels to rise once again, the water flow can be turned on and off simply by changing the position of the outflow pipe. The leveller can be used not only to control beaver pond levels, but to also to restore water flow to culverts. Although the leveller costs more to build than most of the other control systems, it requires less maintenance. Also, it provides landowners the added option of managing beaver ponds as greentree reservoirs for waterfowl, which can mean additional annual revenues from hunting leases.

Figure 3
Figure 3. The Clemson Beaver Pond Leveller. The pond level is regulated by turning the swiveling elbow at the outlet. Here, the elbow is turned so that the outlet is pointed up, causing the pool level to rise above the baffle.

Protecting Drains in Reservoirs and Farm Ponds

Because beavers often use mud and sticks to block water flowing into reservoir and pond drains, protecting water- control structures (drop tubes, risers, standpipes, or whistler tubes) can pose quite a problem. Some measure of control can usually be gained by installing risers so that they open upstream instead of toward the dam and by placing riser structures far from the face of the dam to utilize as deep water as possible. Over time, however, even structures in 6 or more feet of water may become blocked because of the mounding of debris on the pond bottom, and efforts should be made to survey the site regularly so that beaver debris can be removed. Large risers can be protected from clogging by installing mesh bars (at least 5 inches square) to exclude beavers from entering the trash guard box (Figure 4). Because the sound of running water stimulates beavers to work, the use of a downturned "snorkel" (Figure 5) to minimize the sound will increase the effectiveness of most riser protection measures.

Figure 4
Figure 4. Mesh bars installed to protect the riser from clogging.

Figure 5
Figure 5. The use of a downturned snorkel minimizes the sound of running water.

Frequent examination and maintenance of fences, bafflers, and other drainage devices is important. Debris should be removed from clogged structures regularly, and signs of beaver activity should be noted. Watch for the presence of freshly peeled sticks in shallow areas, standing or unusually sluggish water, and new flooding at any time of the year as signs of possible beaver activity.

Controlling Local Populations

On some man-made impoundment's where beaver exclusion devices are repeatedly plugged and where flood control requirements have been compromised to the point that human safety is in question, eliminating the local beaver population using the proper shooting or trapping techniques should be considered. In addition to safety concerns, loss of property value may justify control of local beaver populations. Remember, however, that the removal of the beavers also means gradual loss of the wide range of ecological benefits that they provide. As noted in the following sections, beaver populations are much harder to control near major rivers and streams than in small watersheds.

Shooting

Shooting can be a time- consuming and highly inefficient method of controlling beavers. Several nights or even weeks are required to remove a beaver colony completely. In some situations, however, particularly those where the entire colony need not be removed, some degree of control can be achieved through shooting. Shooting is also useful in conjunction with trapping. In instances where total removal is desired, shooting can be used to take the final few beavers.

Beavers are nocturnal. Therefore, shooting works best just before and just after sunset. Shooting beavers during these hours usually requires a powerful, portable light and much patience.

Shooting is easier and more effective when two people work as a team. One person holds the light and the other does the shooting. The team should take up a position overlooking likely travel routes or in areas identified by fresh cuttings, slides, and tracks. By remaining quiet and periodically scanning the area with the light, the pair can locate and kill the beavers with a shot to the head or spine. Beavers can also be shot when they come to repair dams that have been removed or otherwise damaged, particularly during times of low water.

While any rifle- caliber .22 long rifle or larger may be used to dispatch beavers humanely, a 12- gauge shotgun loaded with buckshot is the recommended firearm because of the ease with which it can be aimed in low light situations. To avoid crippling the beavers, shooters using a shotgun should wait to fire until the beavers are within 20 yards. Retrieve and remove all beaver carcasses, as their presence may cause any remaining beavers to change their patterns, making future shooting efforts considerably more time consuming.

Trapping

If total removal of the colony is desired, trapping is usually necessary. Trapping is not difficult to learn and in many situations provides the most practical and cost- effective way of keeping beaver populations in check. Although trapping is sometimes strenuous, the method can be used to eliminate beaver damage problems in relatively small watersheds and farm ponds.

In trapping, the goal is to remove the entire population, as even one remaining beaver will continue to feed and maintain dams. Catching the last few beavers in well- established populations is often difficult and time consuming. Even after all the beavers have been removed, it is important to check the site regularly because other beavers may move in, making additional control work necessary. Beaver problems are much easier to take care of when they first occur.

A variety of traps and trapping techniques are effective for capturing beavers, and the best trap to use depends on the situation. In North Carolina the three legal trap types are the Conibear 330, the foothold, and the snare.

Using the Conibear 330 Trap

The Conibear 330 trap (Figure 6a) is the most humane trap for beavers. It is designed to instantly kill and hold any beaver that attempts to swim through it. Because of this trap's potential danger to humans and domestic animals, North Carolina law restricts its placement. In Buncombe, Madison, McDowell, and Yancey counties it must be used in water and must be totally submerged. In all other counties, Conibear 330 traps set for beavers can be set up to halfway out of the water but no higher. Whenever possible, Conibear 330 traps should be used only where they can be totally submerged.

Conibear traps can be set in both shallow and deep water and can usually be set faster than foothold traps. Although the Conibear trap is relatively easy to set and place, great care should be taken when using them. Be sure to follow the manufacturer's instructions carefully to avoid injury.

Conibear 330 traps are set by using setting tongs or a 6- foot length of 3/8- or 1/2- inch rope to compress the large springs on each side of the trap so they can be secured with the attached side safety latches. The rope setting method of compressing trap springs is the easiest to use in the field. One end of the rope is run twice through each trap ring of the side spring (Figure 6b) and attached to a loop around the trapper's foot or to a tree. The other end of the rope is then pulled to compress the spring (Figure 6c). A side spring safety latch secures the compressed spring in place. The second spring is compressed and secured in a like manner. After the large springs are secured, the trap jaws are compressed by hand and the trigger catch is set (Figures 6d and 6e). When the trap jaws have been compressed to set the trigger catch, care must be taken to ensure that the side safety latches on the two large springs remain in place. As an added precaution, a safety clip is installed on the compressed trap jaws near the trigger catch.

After the trap has been set and secured with side spring latches and the safety clip, two sticks long enough to protrude from the water are pushed firmly into the mud at a spacing equal to the width of the trap rings on the extended side springs. These sticks are gently placed through the side rings before the side safety latches and the safety clip on the trap jaws are removed (Figure 6f). The trap is then carefully lowered down the sticks (not shown) and into position.

Figure 6
Figure 6. Setting a Conibear 330 trap. The trap is held securely in place with one foot (a). A length of rope can be used to compress the large springs on the side of the trap (b and c; see text). After the side springs are compressed and the safety latches are in place, the trap jaws are compressed by hand (d) and the trigger catch is set (e), taking care to ensure that both side safety latches remain in place. A safety clip (inset) is installed on the compressed trap jaws near the trigger catch. After positioning sticks are in place and the trap has been placed on them, the side spring safety latches and the safety clip are removed (f) and the trap is lowered carefully into the water.

There are two basic ways to set Conibear traps for beavers, one of which is the underwater runway set or dive set (Figure 7). Underwater runways can be located by looking for continuous breaks in the vegetation leading from lodges, bank dens, or feeding areas. In dark water areas, runways can be located by using a pole to probe the bottom for shallow ditchlike depressions that usually have a harder bottom than the surrounding area. Water in the river is usually muddy or discolored. Set the Conibear trap just off the bottom of the runway and hold it in position with stout, dead sticks. (Freshly cut sticks are not recommended because the beaver may stop and strip the bark from them!) Pile debris or sticks on both sides of the trap to funnel the beaver through the trap. As a final touch, place a long stick on the surface of the water parallel to and directly over the trap jaws. This "dive stick" should be long enough to block the entire run area, forcing the beaver to dive under the stick and go through the trap.

Figure 7
Figure 7. Underwater dive set (runway set) using a Conibear 330 trap.

A second place to use the Conibear trap is in front of a dam at a crossover set. Because beavers usually cross the dam at the same place each time, crossover sets are very effective. The Conibear 330 trap is positioned on the upstream side of the beaver dam in the same fashion as the underwater runway set. Remember to attach the trap to a solid stake or tree on the bank with strong wire to make the trap easily retrievable after is has been triggered.

Conibear traps are sometimes set at lodge entrances, but this set may require trapping in deep water. Also, trap- wise beavers may stay in the lodge for up to a week.

Using the Foothold Trap

The effective use of foothold traps requires some skill and knowledge that can be acquired through trapping experience, books, trapping courses, or instruction by an experienced trapper.

The scent mound set (Figure 8) is used where beavers pile mud and leaves 4 to 12 inches high along their travel routes and mark them with castor from their scent glands. Conibear traps or snares can also be used for mound sets. Traps should be set near natural or artificial scent mounds freshened with a castor- based beaver lure. Level a bed for the trap in 2 to 10 inches of water (the steeper the bank, the deeper the trap bed), and set a No. 4 trap with the pan 2 inches off the center of the travel route. No. 5 "Bridger- type" traps are limited by law to underwater sets only; foothold traps with jaw spreads of greater than 71/2 inches are illegal in North Carolina. Attach the trap to a drowning wire made with a one- way sliding lock and 3/32- inch aircraft cable or heavy gauge wire (No. 11 or larger). Stake one end of the wire firmly to the bank and weight the other end with bricks or a cinder block and submerge it in deep water (4 feet deep or more) to pull the wire tight.

Figure 8
Figure 8. Scent mound set using a foothold trap.

Using Snares

Snares can be used to capture beavers anywhere they walk or swim. Snares are light in weight (1/4 pound), easily carried, inexpensive, and very safe to use.

Like the previously described foothold traps, snares may be used in a drowning set whenever water deeper than 4 feet is present. However, drowning sets may not always be desirable, and one advantage of using snares is that they enable the trapper to release unharmed any nontarget species, such as muskrats and otters, caught in the snare.

The equipment needed for snaring beavers includes snares, snare extensions (made out of 3/32- inch cable with an adjustable loop at one end and an S- hook attached to the other), cable cutters, lineman's pliers, an S- hook tool, and a spool of 14- gauge wire. Beaver snares are made from 3/32- inch aircraft cable with a nonlocking cable slide mechanism on one end and a swivel on the other. Nonlocking slides are essential because beavers and nontarget animals can be held around their bodies without strangulation, whereas snares that use the locking slides often found on foothold snares cinch tighter each time the animal pulls against the anchored cable, potentially injuring or killing animals caught by the body. Trappers can avoid causing permanent injury to nontarget animals by checking their snare sets daily.

As with any trap, there is some potential for injury to any nontarget animal that is caught, and any animals that are obviously severely injured should be destroyed. Most nontarget animals can be released by donning heavy leather work gloves before carefully covering the animal with a heavy tarp or jacket or by using a long pole equipped with an adjustable noose to restrain the animal before working the slide lock into an open position. Operations of this nature should be undertaken with a second person.

Beavers caught in any nondrown- ing set should be immediately killed with a pistol, rifle, or shotgun round fired through the base of the head or neck or by a sharp blow with a club.

A runway set (Figure 9) can be used anywhere along natural travel routes or in corridors that can be narrowed enough to force the beaver to move through the snare. Anchor the snare using an extension cable attached to a solid dead tree or stump at least 4 inches in diameter, preferably under water. Where suitable trees are not available, snares can be anchored by attaching the snare extension around the lower end of a tripod configuration constructed of long, stout limbs pushed solidly into the mud.

Figure 9
Figure 9. Snare used in a runway set.

To position the snare, wrap a 24- inch piece of 14- gauge wire around a small branch, leaving about 12 inches of wire free at the top. Set the snare loop about 8 inches in diameter and crimp the free end of the wire just behind the snare slide. With this wire in place, the snare can be positioned as necessary by simply bending the wire. Note that the wire is used only to position the snare and is not intended to hold the beaver. Position the snare with the bottom of the loop approximately 6 inches below the water level and then fence off both sides of the snare with just one or two dead sticks to complete the set.

In the snare slide set the snare is located on the bank with the bottom of the loop placed directly on the ground. Anchor and position the snare as in the runway set, and fence off both sides of the snare loop to force the beaver through the snare. Use a 7- inch loop instead of an 8- inch one to decrease the possibility of tripped but empty snares. This set can be enhanced by placing a castor mound and beaver lure at least 18 inches beyond the snare.

Sources of Additional Information and Assistance

Because of time, health, or financial limitations, many landowners cannot carry out beaver damage control activities on their own. For those landowners suffering severe losses, the North Carolina Wildlife Resources Commission has provided county Extension Centers with a list of trappers willing to render their services. Landowners may also wish to contact NCWRC district biologists or wildlife enforcement officers directly for recommendations on appropriate damage control measures. The NCWRC headquarters (telephone 919- 733- 7291) can provide the names and telephone numbers of the nearest biologists or officers.

Concerns may also be addressed to the U.S. Department of Agriculture's Animal Damage Control (ADC) office in Raleigh at 919- 856- 4124. Agency personnel can provide information on local beaver damage control programs and can suggest sources of beaver damage control equipment and supplies.

Prepared by

Peter T. Bromley, Department Extension Leader, Wildlife Extension, North Carolina State University
Jon F. Heisterberg, Director, Office of Animal Damage Control, US Department of Agriculture
William T. Sullivan, Jr., Research Assistant, Department of Zoology, North Carolina State University
Perry Sumner, Furbearer Project Leader, North Carolina Wildlife Resources Commision
James C. Turner, Extension Assistant, Department of Zoology, North Carolina State University
Ronald D. Wickline, Wildlife Technician, Office of Animal Damage Control, US Department of Agriculture
David K. Woodward, Research Technician, Department of Zoology, North Carolina State University

Illustrations by David Williams

The authors wish to thank Edwin J. Jones, Todd Menke, J. V. Vandenburgh, Nick Walters, and Sam Wiseman fot their reviews of the manuscript.

Support for this publication was provided by the North Carolina Office of Animal Damage Control, USDA-APHIS, and the North Carolina Wildlife Resources Commission.

The use of brand names in this publication does not imply endorsements of the products or services named or criticism of similar ones not mentioned.

11,000 copies of this public document were printed at a cost of $1,760.00, or $.15 per copy.

Published by North Carolina Cooperative Extension Service

Distributed in furtherance of the Acts of Congress of May 8 and June 30, 1914. Employment and program opportunities are offered to all people regardless of race, color, national origin, sex, age, or disability. North Carolina State University, North Carolina A&T State University, US Department of Agriculture, and local governments cooperating.

10/94-11M-TWK-240544

AG-472-4

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