Jimmy D. Taylor

Supervisory Research Wildlife Biologist

USDA-APHIS-Wildlife Services 

National Wildlife Research Center

Corvallis, Oregon

Greg K. Yarrow 

Professor of Wildlife Ecology 

 and Chair

Department of Forestry and 

 Environmental Conservation

Clemson University

Clemson, South Carolina

James E. Miller 

Professor Emeritus

Department of Wildlife, Fisheries 

 and Agriculture

Mississippi State University

MSU, Mississippi

Human-Wildlife Conflicts

The American beaver (Castor canadensis) 

(Figure 1) is known as an “ecosystem 

engineer” because of the benefits their 

dams provide to biological diversity and 

ecosystem function. It also is considered a 

“keystone species” because of its ability to 

transform its environment, creating new 

habitats upon which other species depend. 

Despite the many positive benefits 

beavers provide through foraging and dam 

building, beavers also create conflict with 

people when their activities cause 

damage. The authors of this publication 

acknowledge and appreciate the many 

positive benefits that beavers provide; 

however, the focus of this publication is to 

provide basic information on beaver 

ecology, damage, and management. In 

general, beavers cause damage by 1) 

gnawing on trees or crops; 2) flooding 

trees, crops, property, or transportation 

corridors (roads, airports, railways) through 

dam building; and 3) degrading and 

destabilizing banks and levees through 

burrowing. 

Wildlife Damage Management 

Technical Series

U.S. Department of Agriculture

Animal & Plant Health Inspection Service

Wildlife Services

March 2017 Beavers

Figure 1. American beaver (Castor canadensis).

Quick Links

Human-Wildlife Conflicts 1

Damage Identification 2

Management Methods 3

Economics 12

Species Overview 12

Legal Status 16

Glossary & Key Words 17

Resources 18 

Appendix 21 
Landscapes

Beavers occupy a variety of landscapes from desert to 

taiga, although beaver-human conflicts are fairly consistent 

across all landscapes. In general, beavers cause damage 

to human resources by 1) gnawing on trees or crops; 2) 

flooding trees, crops, property, or transportation corridors 

(roads, airports, railways) through dam building; and 3) 

degrading and destabilizing banks and levees through 

burrowing. The scale and scope of beaver damage to 

human resources are dependent on many factors including 

floodplain size, water availability, beaver population size, 

and juxtaposition of beavers and humans. Not all beavers 

build dams; however, beaver dams are generally 

constructed prior to seasonal high water events. 

Beavers will gnaw on trees of all sizes and most species 

(Figure 2). Beavers, like most rodents, need to gnaw to 

keep their teeth at the proper length. Thus, they 

sometimes girdle trees that they do not fell. Large diameter 

trees are sometimes felled by beavers, who feed on twigs 

and haul small stems to dams and lodges. Beavers 

sometimes fell large trees that they do nothing with, such 

as conifers. The value of trees and crops damaged by 

beavers may depend on their aesthetic, cultural, 

ecological, economic, or historical importance. The 

damming of one small stream; however, may cause 

potential harm to human life and overshadow all other 

values. 

Figure 2. Beaver damage to trees.

Page 2

Figure 3. Beaver damage and the collapse of beaver dams can lead to 

structural damage of roadways and blocked culverts.

WDM Technical Series—Beavers

Human Health and Safety

Residential buildings are sometimes damaged when large 

beaver dams fail, generally due to rapid increases in water 

velocity. Risk to residents is high during flash flood events, 

and reports of economic damage to structures during 

single events are estimated in the millions of dollars. 

Unexpected beaver dam failure also has led to the 

collapse of railroad structures, roads, and airport runways 

(Figure 3). These events not only result in significant 

economic loss, but also have led to human fatalities. 

Beavers are hosts for several ectoparasites and internal 

parasites including nematodes, trematodes, and 

coccidians. Giardia lamblia is a pathogenic intestinal 

parasite transmitted by beavers, which has caused 

human health problems in water supply systems. Beavers 

also are known to carry tularemia, which can be 

transmitted to humans through direct contact. 

The effects of beaver behavior are viewed as positive or 

negative depending on people’s perceptions and 

tolerance levels. Habitat modification by beavers, caused 

primarily by dam building, is often beneficial to fishes, 

Damage Identification
furbearers, reptiles, amphibians, bats, waterfowl, 

shorebirds, cavity nesting birds, and mammals. However, 

when this modification comes into conflict with human 

objectives, the perceived negative impacts may far 

outweigh the benefits. Identifying beaver damage generally 

is not difficult. Signs include the presence of dams; 

plugged culverts, bridges, or drain pipes resulting in 

flooded lands, timber, roads, and crops; girdled, partially 

girdled, or felled trees; and burrows in banks and levees. 

There are several lethal and nonlethal damage 

management tools and techniques for resolving beaver 

conflicts. Lethal methods include shooting and trapping. 

Although lethal methods may be appropriate in many 

situations, modern wildlife damage management also 

includes several non-lethal options. Non-lethal techniques 

for reducing beaver damage include exclusion, habitat 

modification, repellents, and relocation. To be the most 

effective at reducing damage, it is recommended that 

several management methods be used in combination. 

Flooding by beavers generally occurs where beavers dam 

streams or plug culverts. Conflict resolution in either case 

requires human intervention to control water levels. 

Mechanical removal of dam material often is used to seek 

immediate results (Figure 4); however, beavers can rapidly 

replace dam material. Under certain hydrological 

conditions, flooding can return within 24 hours. Lethal 

trapping is used to supplement dam removal with a goal to 

remove the dam-building beavers from the area. Similarly, 

live-capture and relocation are used to supplement 

mechanical dam removal where permitted by state law. 

While these techniques generally provide immediate 

success at the point of damage, other beavers may occupy 

dam sites up- or downstream and flooding reoccurs. 

Furthermore, relocating damming beavers may lead to 

damage at the release site, and cause undue stress to 

relocated beavers. 

Use of flow devices modifies beaver habitat and offers a 

more long-term solution to flood control (see Habitat 

Page 3

Figure 4. Damage associated with flooding by beavers generally occurs 

where beavers dam streams or plug culverts. Mechanical removal of dam 

material often is used to seek immediate results.

U.S. Department of Agriculture

Management Methods

Modification section). Flow devices should be 

implemented, where applicable, in beaver management 

plans before damage occurs, and may be used in 

conjunction with trapping and mechanical dam removal 

after initial flooding is abated. 

Repellents and tree exclusion are not useful in controlling 

flooding by beavers; however, they may help reduce tree 

cutting. These techniques may be integrated into 

management plans along with lethal control measures 

where protection of high-value trees justifies costs of 

installation, application, and maintenance. 

Habitat Modification

Flow devices are tools that combine exclusion and 

deception to maintain positive water flow where beavers 

dam culverts and streams. Flow devices are often most 

effective at dams or culverts when corrugated pipe is used
in conjunction with an exclusion fence (Figure 5). Flexible 

pipe and round fence also can be used to reduce water 

levels at dams (Figure 6). Clemson pond levelers are 

another example of a flow device (Figure 7). They are most 

often utilized to control water at dams, but also can be 

used with culverts. 

Breaching dams may provide immediate relief, but it does 

not prevent rebuilding and is not a long-term solution. 

Mechanical breaching is a common method used to 

reduce or remove dams. This may range in effort from a 

few minutes with a rake or hoe, to several hours with heavy 

machinery. Other methods, including high pressure water 

pumps and explosives, can breach dams; however, they 

require specialized training and are generally done by 

trained government employees. 

Exclusion

To protect trees from gnawing, total exclusion with fencing 

(e.g., chain link) is the only proven technique. However, this 

technique is often cost prohibitive and is not practical in 

uneven terrain. Wrapping individual trees with wire mesh 

and T-posts can reduce gnawing; however, beavers can 

chew through wire. Additionally, changing water levels may 

submerge the fencing or other barriers, providing beavers 

foraging opportunities. Seedling tubes are ineffective for 

protecting individual seedlings from beavers. 

Figure 5. An example of a flow device using an exclusion fence at the culvert 

intake (lower right corner), corrugated pipes and round fences.

Page 4

Figures 7. An example of a Clemson pond leveler used to control the water level at a dam.

WDM Technical Series—Beavers

Figure 6. An example of a flexible pipe with a round fence used to control 

the water level at a dam.
To reduce flooding, fencing may be placed upstream of 

culverts to exclude beavers from damming culvert intakes. 

These fences may be referred to as deep water fences or 

culvert fences. Culvert fences can be effective when 

maintenance requirements are low; however, culvert 

fencing is most effective when combined with corrugated 

pipe to create a flow device (see Habitat Modification). 

Exclusion devices such as culvert grates or T-culverts, 

which are placed directly on or adjacent to culverts, are not 

recommended to reduce flooding. They typically catch 

floating debris and require a lot of maintenance. 

Additionally, beavers can dam the device which has the 

same function as directly plugging the culvert. 

Frightening Devices

Not applicable.

Repellents

There are no chemical repellents registered for beavers. 

General herbivore repellents will not deter beavers from 

damming or plugging water flow structures, but they may 

be useful in protecting vegetation. Although herbivore 

repellents do not deter beavers from gnawing through 

trees, they can reduce the palatability of plants and 

seedlings when applied directly to the foliage. Research 

has shown that textural repellents (e.g., masonry grade 

sand and latex paint) may reduce tree damage. One study 

showed that treating trees with red maple extract inhibited 

feeding by beavers, but this may not be effective where red 

maple does not occur naturally. 

Predator odors have also been shown to have some effect 

at deterring beaver, but over time may become less 

effective without the presence of predators. The success of 

any repellent is dependent on the palatability of the 

treated species and the availability of alternative food 

sources. During certain seasons and when food is scarce, 

repellents may be completely ineffective. Other studies 

have used a combination of dam removal and repellent 

soaked rags (Thiram 80 and/or paradichlorobenzene) to 

discourage beavers with varying degrees of success. It has 

been shown that beavers are less likely to colonize sites 

treated with a mixture of beaver castoreum anal gland 

secretion than untreated sites. It may be possible to 

prevent beavers from settling in an area by treating the 

area with castoreum; however, the feasibility of such an 

approach is still unknown.

Toxicants

None registered.

Shooting

In some states, it is legal to shoot beavers. Before 

attempting to shoot beavers, check regulations, and if 

applicable, secure permits and notify local law 

enforcement personnel of your intentions.

Beavers are most active from late afternoon to shortly after 

daybreak, depending on the time of year. They usually 

retire to a lodge or bank den for the day. Therefore, if night 

shooting is not permitted, the early evening and early 

morning hours are most productive. Creating a breach or 

break in the dam may draw beavers to this spot making it 

easy to locate and target them. Choice of weapons 

depends on the range and situation. Most shooting is done 

with a shotgun at close range at night. Shooting alone is 

generally not effective in eliminating all beaver damage in 

an area. However, shooting can be used to quickly reduce 

immediate conflict by removing damage-causing 

individuals.

Trapping

Trapping is the most commonly used method to reduce 

beaver damage. The effectiveness of trapping is strongly 

dependent upon the trapper’s knowledge of beaver habits 

and food preferences, his/her ability to detect and “read” 

beaver sign, and his/her ability to select, use, and properly 

place the trap. 

A good trapper with a dozen traps can generally trap all the 

beavers in a given pond (behind one dam) in a week’s 

worth of trap nights. Obviously in a large watershed with 

several colonies, more trapping effort will be required. 

Those with trapping experience and some outdoor “savvy” 

U.S. Department of Agriculture Page 5
can become an effective beaver trapper in a short time. In 

an area where beavers are common and have not been 

exposed to trapping, anyone experienced in trapping can 

expect good success. Additional expertise and improved 

techniques will be gained through experience.

Trapping regulations vary from state to state. Some types 

of traps and trapping methods, although effective and legal 

in some states, may be prohibited by law in other states. 

Individual state regulations must be reviewed annually 

before beginning a trapping program.

In some states where beavers have become serious 

economic pests, special regulations and exemptions have 

been passed to allow for increased control efforts. For 

example, some states categorize beavers as “predators” 

and allow their removal throughout the year. Others, 

however, prohibit trapping except during established fur 

trapping seasons. Some states allow exemptions for the 

removal of beavers only on lands owned or controlled by 

persons who are experiencing damage. 

A variety of trapping methods and types of traps are 

effective for beavers. In 2006, the Association of Fish and 

Wildlife Agencies published the Best Management 

Practices for Trapping in the United States (http://

www.fishwildlife.org/files/Introduction_BMPs.pdf). A 

chapter for beaver is included which details trapping 

methods, as well as several trap manufacturers and trap 

designs (http://www.fishwildlife.org/ files/ 

Beaver_BMP_2016.pdf). Although not all manufacturers 

are included in this manual, it provides insight into the 

commonly accepted standards for beaver traps and 

trapping methods. 

When trapping for beaver, special attention should be 

given to look for signs of river otter. In areas where both 

species occur, river otters occupy the same habitat and are 

frequently caught in beaver traps. To avoid capturing river 

otter, search for their signs and avoid setting traps at high 

probability otter travel-ways, particularly paths connecting 

bodies of water, shoreline trails, and inactive beaver bank 

dens or lodges. One should also attempt to avoid lures that 

may attract river otters. Over trapping an area may also 

increase the risk of capturing otter. Set an appropriate 

number of traps for the number of beavers perceived in an 

area and avoid leaving traps for extended periods of time. 

Carry a catchpole or similar device to assist with releasing 

live otters. 

Bodygrip Traps

The bodygrip trap is one of the most effective lethal traps 

for capturing beaver. This trap kills beavers almost 

instantly. When properly set, the trap also prevents any 

escape by a beaver, regardless of its size. Designed 

primarily for water use, it is equally effective in deep and 

shallow water. Generally, only one trap per site is 

necessary. The trap exerts tremendous pressure and 

impact when tripped. Appropriate care must be exercised 

when setting and placing the trap. Special caution should 

also be taken when using bodygrip traps in urban and rural 

areas where pets (especially dogs) roam free. See the Trap 

Sets section to select the best set to avoid capturing nontarget species.

If using a bodygrip trap, additional equipment, such as an 

axe, hatchet or large cutting tool; hip boots or waders; wire; 

and wire cutters, may be useful. With bodygrip traps, some 

individuals set the trap using a tool called “setting tongs.” 

Others use a piece of 9 or 13 mm (3/8 or 1⁄2 in) nylon rope. 

Most individuals who are experienced with these traps use 

only their hands to set them. Regardless of the techniques 

used to set the trap, care should be exercised. 

Earlier models of bodygrip traps came with round, heavy 

steel coils which were dangerous to handle unless properly 

used in setting the trap. They are not necessary to safely 

set the trap. However, the two safety hooks, one on each 

spring, must be carefully handled as each spring is 

depressed, as well as during trap placement. On newer 

models an additional safety catch (not attached to the 

springs) is included for extra precaution against 

inadvertent spring release. The last step before leaving a 

set trap is to lift the safety hook attached to each spring 

and slide the safety hook back from the trap toward the 

spring eye, making sure to keep hands and feet safely 

away from the center of the trap. If the extra (unattached) 

safety catch is used, it should be removed before the 

safety hooks are attached to the springs to keep it from 

Page 6 WDM Technical Series—Beavers
getting in the way of the movement of the safety hooks. 

Bodygrip traps are best set while on solid ground with dry 

hands. Once the springs are depressed and the safety 

hooks are in place, the trap or traps can be carried into the 

water for proper placement. Stakes are needed to anchor 

the trap down. In most beaver ponds and around beaver 

dams, plenty of suitable stakes can be found. At least two 

strong stakes, preferably straight and without forks or 

snags, should be chosen to place through each spring eye 

(Figure 8). Additional stakes may be useful to put between 

the spring arms and help hold the trap in place. Do not 

place stakes on the inside of spring arms. Aside from 

serving to hold the trap in place, these stakes also help to 

guide the beaver into the trap. Where needed, they are 

also useful in holding a dive stick at or just beneath the 

water surface (Figure 9). If necessary, the chain and circle 

attached to one spring eye can be attached to another 

stake. In deep water sets, a chain with an attached wire 

should be tied to something at or above the surface so the 

trapper can retrieve the trap. Otherwise the trap may be 

lost.

There are many sets that can be made with a bodygrip trap 

(for example, dam sets, slide sets, lodge sets, bank den 

sets, “run”/trail sets, under log/dive sets, pole sets, under 

ice sets, deep water sets, drain pipe sets), depending on 

the trapper’s capability and ingenuity. In many beaver 

ponds, however, most beavers can be trapped using dam 

sets, lodge or bank den sets, sets in “runs”/trails, dive sets 

or sets in slides entering the water from places where 

beavers are feeding. Beavers swim both at the surface and 

along the bottom of ponds, depending on the habitat and 

water depth. Beavers also establish runs or trails which 

they habitually use in traveling from lodge or den to the 

dam or to feeding areas, much like cow trails in a pasture. 

Place traps directly across these runs, staked to the 

bottom (Figure 10).

Use a good stake or “walking staff” when wading in a 

beaver pond to locate deep holes, runs, or trails. The staff 

can also help locate good dive holes under logs as you 

follow runs or trails. In older beaver ponds, particularly in 

bottomland swamps, it is not uncommon to find runs and 

lodge/bank den entrances where the run or hole is 0.6-0.9 

m (2-3 ft) below the rest of the impoundment bottom.

To stimulate nighttime beaver movement, tear a hole in a 

beaver dam and get the water moving out of a pond. 

Beavers quickly respond to the sound of running water as 

well as to the current flow. Timing is also important if you 

plan to make dam sets. Open a hole in the dam about 46-

60 cm (18-24 in) wide and 60-90 cm (2-3 ft) below the 

water level on the upper side of the dam in the morning. 

This will usually move a substantial amount of water out of 

the pond before evening. Set traps in front of the dam

Page 7

Figure 8. Basic method of setting and staking a double-spring bodygrip trap.

U.S. Department of Agriculture

Figure 9. Double-spring bodygrip trap used in a dive set. Note the dive stick 

placed at the top of the set to encourage the beaver to dive under water 

through the trap.
opening late that same evening. Two problems can arise if 

you set a trap in the morning as soon as a hole is made: 1) 

by late evening, when the beavers become active, the trap 

may be out of the water in and ineffective; or 2) a stick, 

branch, or other debris in the moving water may trip the 

trap, rendering it ineffective.

The best dam sets are placed about 30-45 cm (12-18 in) 

in front of and on the upstream side of the dam. Using 

stakes or debris on either side of the trap springs, create a 

channel to encourage the beaver to swim through the jaws 

of the trap. Always set the bodygrip trap trigger in the first 

notch to prevent debris from tripping it before the beaver 

swims into the trap. The two heavy gauge wire trippers can 

be bent outward and the trigger can be set away from the 

middle, if necessary, to keep debris from tripping the trap. 

This can also keep small beaver, fish or turtles from 

accidentally springing the trap. In areas where river otters 

are present, use a “side-parallel” position on the trigger by 

moving the wires to one side of the bodygrip trap. Placing a 

stick in front of the wires will help prevent an otter from 

hitting the wires. Using traps with 2-way or adjustable 

tension triggers also prevents non-target captures. 

Foothold Traps

Double-spring foothold traps have been used for hundreds 

of years and are still very effective when used properly 

(Figure 11). Use at least No. 3 double (long) spring or coil 

spring type foothold traps or traps of equivalent jaw size, 

spread, and strength. Include a submersion set 

attachment with a weight when using a foothold trap. 

When a beaver trips a foothold trap, it will immediately 

head for the water. The submersion set with a weight will 

hold the trapped beaver underwater until it drowns. If a 

submersion set attachment is not used, it is likely that the 

beaver will escape.

Placement is even more critical with foothold traps than 

with the bodygrip traps. Place foothold traps at the water’s 

edge, slightly underwater, with the pan, jaws, and springs 

covered lightly with leaves or debris or pressed gently into 

the soft mud. Make sure there is a cavity under the pan so 

that when the beaver’s foot hits the pan, it will trigger the 

trap and allow the jaws to close. Place traps off-center of 

the beaver trail or run to prevent “belly pinching” or 

missing the foot or leg. With some experience, beaver 

trappers learn to make sets that catch beavers by a hind 

leg rather than a front leg. The front leg is much smaller 

and easier to pull out of the trap. To avoid capturing river 

otter, use castor mound sets with traps placed 20-25 cm 

(8-10 in) deep in the water.

When using foothold traps, it may be beneficial to create 

two trap sets in the beaver’s slide, run, dam, or feeding 

place to increase trapping success. In some situations, a 

combination of trapping methods can shorten trapping 

time and increase success.

Trappers have come up with unique methods of making 

submersions sets. One of the simplest and most practical 

is a slide wire with a heavy weight attached to one end, or 

with an end staked in shallow water (i.e., less than 0.9 m 

(3 ft) deep). The other end of the wire is threaded through 

a hole in a small piece of angle iron. The trap chain is 

attached to a hole in the other end of the angle iron. The 

end of the wire is then attached to a tree or stake driven 

into the bank (Figure 12). When the beaver gets a foot or 

leg in the trap, it immediately dives back into the water. As 

the angle slides down the wire, it prevents the beaver from 

reaching the surface. The angle iron will not slide back up 

the wire, thus preventing the beaver from coming up for 

air. Trappers should be prepared to quickly and humanely 

dispatch a beaver that is caught in a trap and has not 

drowned. 

Page 8 WDM Technical Series—Beavers

Figure 10. Bodygrip trap set half-submerged in a beaver run with trigger on 

the bottom jaws.
The foothold trap set in lodges or bank dens is also 

effective, especially for trapping young beavers. Place the 

set on the edge of the hole where the beaver first turns 

upward to enter the lodge or den, or place it near the 

bottom of the beaver’s dive hole. To set the trap so that a 

swimming beaver’s foot can trip the pan, keep the trap’s 

jaws and pan from resting on the bottom of the pond by 

pulling the springs backward. Stake the set close to the 

bottom or wire the trap to a log or root on the bottom. This 

avoids needing submersion weights, wires, and angle 

irons. Generally, more time and expertise are needed to 

make effective sets for foothold traps and snares, than 

bodygrip traps.

Use castor scent or freshly cut cottonwood, aspen, willow, 

or sweetgum limbs to entice beaver to foothold trap sets. 

Bait or scent is especially useful around beaver castor 

mounds and slides along the banks or dams. Most 

trappers who use bodygrip traps do not employ bait or 

scent. In some states it is illegal to use bait or scent.

Live Traps

Suitcase-style live traps are becoming more widespread 

due to lethal trapping restrictions. The traps are rarely 

used, however, except by professionals in urban areas 

where anti-trap sentiment or other reasons prevent the 

lethal trapping of beavers. These traps are heavy (typically 

weighing around 13.6 kg (30 lbs)) and costly, particularly 

Page 9

Figure 11. Number 4 double-long spring trap.

U.S. Department of Agriculture

Figure 12. Diagram of a traditional drowning set. Note the a food lure with 

shaved branches can be used instead of castor.

when multiple traps are required. Muller-Schwarze and 

Haggart (2005) recommend the Hancock live trap (Figure 

13), however, other manufacturers are available. Most 

suitcase traps are similar in design and, like the Hancock 

trap, consist of two spring loaded jaws surrounded by wire 

mesh. A trigger plate is located in the center of the trap, 

which when triggered, causes the trap to close and 

surround the beaver in wire mesh like the closing of a 

suitcase (Figure 14). Safety should be considered when 

using a suitcase style trap. Although not as dangerous as a 

bodygrip trap, the springs on the suitcase traps are strong 

and may cause injury. One problem is that the safety 

device for the Hancock live trap is located near the trigger 

plate inside the trap, causing the trapper to reach inside 

the trap to release the safety. A piece of wire or twine can 

be tied to this safety ring, which will allow the user to 

disengage the safety from outside the trap. A more 

involved and intricate safety modification is also described 

in Muller-Schwarze and Haggart (2005). 

Snares

Non-powered cable devices (snares) can be a very costeffective method for capturing beavers (Figure 15). Snaring 

equipment costs far less than trapping equipment and is 

more convenient to use in many situations. In addition, 

beavers can be captured alive by snaring and released 

elsewhere if desired and legal.
Snare placement is similar to trap placement. First, look for 

runways and fresh sign that indicate where beaver 

activities are focused. Find a suitable anchor such as a 

large tree, log, or root within 3 m (10 ft) of the runway 

where the snare will be set. If necessary, anchor snares 

with rods driven into the ground. Attach three, 14-gauge 

wires to the anchor so that each can swivel freely. Cut each 

wire to length so they reach about 30 cm (1 ft) past the 

runway. Twist the wires together to form a strong braided 

anchor cable. Drive a supporting stake into the ground 

near the runway and wrap the free end of the anchor cable 

around it twice. Prepare a new, dyed, No. 4 beaver or 

coyote snare, consisting of 107 cm (42 inches) of 2.4 mm 

(3/32-inch) steel cable with an attached wire swivel and 

slide lock. Twist the free ends of the three anchor wires 

around the wire swivel on the end of the snare cable. 

Wrap the longest anchor wire around the base of the wire 

swivel and crimp it onto the snare cable about 5 cm (2 in) 

from the swivel. Use both the stake and the supporting 

anchor wire to suspend a full-sized loop about 10 cm (4 in) 

above the runway. If necessary, use guide sticks or other 

natural debris to guide beaver into the snare.

The described snare set is very common, but there are 

several variations and sets that can be used. Snares are 

frequently placed under logs, near bank dens, and next to 

castor mounds. Drowning sets can be made using 

underwater anchors, slide cables, and slide locks.

Snares should be checked at least every 24 hours. 

Dispatch snared beavers with a small caliber gunshot to 

the head. Beavers can be chemically immobilized and 

transported to suitable sites for release, if desired and 

legal.

Snares must be used with great care to avoid capturing 

non-target animals. Avoid trails or areas that are used by 

livestock, deer, or dogs. To avoid capturing river otter, use 

a 23-25 cm (9-10 in) loop with a 10 cm (4 in) loop stop. 

Check with your local wildlife agency for regulations 

associated with trapping and snaring. Snaring is not 

allowed in some states.

Page 10 WDM Technical Series—Beavers

Figure 13. A Hancock live trap (suitcase-style) set along a streambank with a 

scent stick placed in the back of the trap. 

Figure 15. Diagram of a non-powered cable device (snare) set with bait. 

Figure 14. Beaver captured in a suitcase-style live trap using a bank set
For more information about the use of snares see A Guide 

to Using Snares for Beaver Capture (Weaver et al. 1985), 

Using Snares to Live-Capture Beaver, Castor canadensis

(McKinstry and Anderson 1998) and Use of Snares to LiveCapture Beavers (McNew et al. 2007) listed at the end of 

this publication.

Fertility Control

Fertility control using immunocontraception is gaining 

popularity as a nonlethal method; however, it has not been 

tested for use with beavers. Surgical sterilization of the 

adult male or female beaver in a colony has been shown to 

reduce fecundity and alter beaver behavior. This method 

is not a practical solution for managing large, free-ranging 

beaver populations because it is expensive, time 

consuming, and involves surgery. Furthermore, 

sterilization does not reduce beaver damage. 

Handling

When handling any wild animal, including beavers, wear 

disposable latex or nitrile gloves. Be sure to keep your 

distance from the beaver’s mouth and feet. Beavers can 

reposition themselves quickly and cause severe damage 

from biting and clawing. A restraining or catch pole may be 

used to keep a beaver penned for a short period of time. 

As a rule of thumb, thoroughly wash your body and clothes 

after trapping and handling beavers to reduce chances of 

contracting a zoonotic disease, such as tularemia. 

Relocation

Relocation has been effectively used to restore beaver 

populations in areas where they were previously extirpated. 

More recently, efforts to restore and enhance wetlands 

through beaver relocation have generally failed. Reasons 

for this include: 1) relocated beaver often move great 

distances from release sites, and 2) relocated beaver have 

low survival rates because of predation and disease.

In general, relocation is not a recommended management 

method and is often prohibited in many states. In states 

that allow beaver relocation, one should consider both the 

benefits and risks involved before initiating a relocation 

program. Will beavers stay at the release site? Will they 

create the desired effects (i.e., increase biodiversity) or 

undesirable effects (i.e., human-beaver conflicts)? Will 

relocation cause increased disease risk with local native 

species? 

Euthanasia

According to the 2013 American Veterinary Medical 

Association (AVMA) Guidelines on Euthanasia, “approaches 

to euthanasia that ignore recent advances in technology, 

and that do not minimize risks to animal welfare, 

personnel safety, and the environment for a particular set 

of circumstances, are unacceptable.” Most people will not 

have access to wildlife pharmaceuticals to euthanize 

beavers. However, when possible, the use of a sedative 

followed by an intracardiac injection of barbituates is an 

acceptable method of euthanasia for free-ranging wildlife, 

such as beavers. 

Inhaled agents are not a practical methods of euthaniasia 

for beavers given the beaver’s ability to hold its breath for 

several minutes. Adjunctive methods such as 

exsanguination, cervical dislocation, and thoracic 

compression are not practical due to the physical build of 

the species. 

A gunshot to the head (targeted to destroy the brain) is an 

AVMA-approved method of euthanasia for free-ranging, 

captured, or confined beavers. Where guns are prohibited, 

manually applied blunt force trauma to the head may be 

used to euthanize beavers. 

Disposal

Check your local and state regulations regarding carcass 

disposal.

U.S. Department of Agriculture Page 11
There are a limited number of economic studies on beaver 

damage and most include outdated statistics. A study in 

the late 1970s in Mississippi estimated annual loss to 

agriculture (including timber) at $2.5 million. Another 

Mississippi study estimated beaver damage to timber 

ranged from $25 to $118 per hectare, a potential annual 

economic loss of $215 million in 1985 U.S. dollars. A 2011 

economic study evaluating Mississippi’s Beaver Control 

Assistance Program (BCAP) found that for every dollar 

spent on BCAP between $39.67 and $88.52 were saved 

from reduced beaver damage to timber and the state’s 

economy.

Economical tradeoffs between the potential loss of a 

resource (e.g., estimated value of timber at harvest or the 

cost of repairing a damaged road) and the cost of beaver 

management should be assessed prior to implementing a 

beaver management plan. 

It is important to identify and anticipate beaver problems in 

advance. Once beaver colonies become well-established, 

management can be difficult and costly. For instance, 

management can be impeded if adjacent landowners do 

not allow beaver management on their property. In this 

situation, long-term strategies are necessary to achieve 

management goals.

Identification

The American beaver (Castor canadensis) belongs to the 

Family Castoridae in the Order Rodentia. It is one of two 

extant beaver species. The other species is its Eurasian 

counterpart, the European beaver (Castor fiber). 

Physical Description

The American beaver is the largest rodent in North America 

(Figure 16). Most adults weigh from 16 to 23 kg (35 to 50 

lbs), although individuals can exceed 45 kg (100 lbs). 

The beaver is a stocky rodent adapted for aquatic 

environments. Many of the beaver’s features enable it to 

remain submerged for long periods of time. It has a 

valvular nose and ears. Its lips close behind four large front 

(incisor) teeth. Each of its feet has five digits. The hind feet 

contain webbed skin between each digit to aid in 

swimming and a split claw on the second digit that is used 

for grooming. The front feet are small in comparison to the 

hind feet (Figure 17). The underfur is dense and generally 

gray in color, whereas the guard hair is long, coarse and 

ranging in color from yellowish brown to black, with reddish 

brown being the most common color. The prominent tail is 

flattened dorsoventrally, scaled, and nearly hairless. It is 

used as a prop while the beaver is sitting upright and for a 

rudder when swimming. Beavers also use their tail to warn 

others of danger by abruptly slapping the surface of the 

water. The beaver’s large incisors are bright orange in color 

on the front and grow continuously throughout its life. 

These incisors are beveled so that they are continuously 

sharpened as the beaver gnaws and chews while feeding, 

girdling, and cutting trees. If a beaver is unable to chew, its 

teeth would overgrow and eventually cause its death. 

The most common way to distinguish between the sexes 

(unless the female is lactating) is to feel for the 

Page 12 WDM Technical Series—Beavers

Figure 16. American beaver with radio-transmitter attached to its tail. 

Economics

Species Overview
presence (male) or absence (female) of a baculum or 

penile bone. It is also possible to distinguish between 

males and females by inspecting the cloaca (the single 

urogenital opening on both males and females). Anterior to 

the anus two openings are present in the female, with only 

one in the male. Anal gland secretions (AGS) also vary in 

color and viscosity between the sexes, with the males AGS 

generally being darker and more viscous. None of these 

field techniques are completely reliable and require 

experience to differentiate. If sexing is crucial, a genetic 

analysis is recommended.

Range

American beavers are found throughout North America, 

except for the extreme arctic tundra, parts of peninsular 

Florida, and desert areas devoid of free-flowing water 

(Figure 18). The species may be locally abundant wherever 

aquatic habitats are found. Populations of C. canadensis

are exotic to parts of Europe where they were introduced 

and coexist with the Eurasian beaver (C. fiber). They also 

are present in the Tierra del Fuego region of South America 

where they are considered an invasive species. 

Voice and Sounds

Beavers communicate by vocalizations, posture, tail 

slapping, and scent posts or castor mounds placed around 

banks and dams (see Tracks and Signs). 

Tracks and Signs

The beaver’s castor glands secrete castoreum, a 

substance that is deposited on mud mounds to mark 

territorial boundaries (Figure 19). These scent posts are 

found year-round in active ponds, but are more frequent 

during the spring, which may coincide with dispersal. Signs 

of beaver activity also include tree cutting/girdling, slides, 

and fecal pellets. 

The presence of active dams and lodges are indicative of 

beavers, but are not good indicators of beaver presence or 

relative abundance. Many beavers live in bank dens 

among steams and rivers and do not build dams. Bank 

dens can be identified during low water. In areas with 

harsh winter habitat, food caches may be found near 

lodges. 

U.S. Department of Agriculture Page 13

Figure 17. Beaver tracks.

Figure 18. Range of beaver in North America.
Reproduction

Beavers are socially monogamous, however, recent genetic 

studies have shown that they do participate in 

promiscuous mating if opportunities are available. 

Copulation may take place either in the water, lodge, or 

bank den.

After a gestation period of approximately 128 days, female 

beavers generally give birth to 3 or 4 kits between March 

and June, and nurse them for 6 weeks to 3 months. The 

kits are born fully furred with their eyes partially opened 

and incisors erupted through the gums. They generally 

become sexually mature after 1.5 years.

Denning 

Beavers build lodges (Figure 20) or bank dens, depending 

on the available habitat. All lodges and bank dens have at 

least two entrances. The lodge or bank den provides 

shelter and protection from predators, and is used for 

raising young, sleeping, and storing food. In extremely cold 

environments where water freezes for long periods of time, 

beavers also cache food near lodges and bank dens for 

easy access. Lodges are typically constructed in lentic 

systems (e.g., lakes, ponds, swamps); whereas, bank dens 

are generally used by beavers in lotic systems (e.g., 

streams, rivers) where lodges would not withstand rapid 

water flow.

Mortality

In the absence of predators, beavers have relatively long 

life spans, with individuals known to have lived up to 21 

years. Most, however, do not live beyond 10 years. 

Beavers have only a few natural predators besides people, 

including coyotes and bobcats. River otters and mink are 

known to prey on young kits. In other areas, bears, 

mountain lions, wolves, and wolverines may prey on 

beavers. In the southeastern states, alligators are known 

to be occasional predators of both juvenile and adult 

beavers; however, their predation has limited impact on 

beaver damage. 

Population Status

Methods to estimate beaver populations are generally 

unreliable; therefore, their population status is unknown. 

Relative measurements, such as trapper harvest and 

nuisance complaints, are often used to detect trends; 

however, this does not reflect population size. In areas 

where beavers live in bank dens and do not build dams, 

their population size is likely underestimated. 

Page 14 WDM Technical Series—Beavers

Figure 19. Castor mound created by a beaver to mark its territory.

Figure 20. Cross section of a beaver lodge.
Habitat

Beavers are found in a variety of habitats from sea level to 

3,400 m (>11,000 ft) and are generally found wherever 

there is a constant source of water. Example habitats 

include rivers, streams, lakes, ponds, swamps, roadside 

ditches, canals, mine pits, oxbows, railroad right-of-ways, 

water treatment facilities, and below natural springs or 

artesian wells. 

Beavers build dams to increase water surface area, which 

increases survival and the growth of desired foods. 

However, not all beavers build dams. Where beavers build 

dams, the slope of the land is generally between 1 and 5 

percent. 

Dam building is thought to be stimulated by running water; 

however, this is not always the case. The length or height 

of a dam varies depending upon the amount and flow of 

water behind it. While wood is a main component of dams, 

beavers also use other available materials found nearby, 

such as fence posts, bridge planking, crossties, rocks, and 

wire. In areas where wood is scarce or unavailable (e.g., 

canals in large agricultural fields), beavers may build dams 

with corn stalks, soybean vines, sorghum stalks, other 

plant materials, and mud. Well-constructed dams generally 

consist of several interwoven branches perpendicular to 

the flow of current. Beavers carry mud and pack it 

between the branches using their front legs. Some dams 

last many years and others are ephemeral (lasting days or 

weeks) depending on water flow and the geomorphology of 

the stream.

Bridges and culverts used to channel water under 

transportation corridors (roads, railways, runways, etc.) 

provide easy damming opportunities for beavers because 

they require little work. 

A beaver’s dam and its subsequent pond provides safety 

from predators. The flooding of outside stream channels 

also increases the growth and availability of desirable 

forage. Thus, dam-building beavers help create their own 

habitat. 

Behavior

Beavers are semi-aquatic and herbivorous. It is not 

uncommon to see beavers during the day; however, they 

are generally nocturnal or crepuscular. The phrase “busy 

as a beaver” is appropriate as they are often seen outside 

of dens/lodges, constructing or maintaining dams. Beavers 

are territorial. A colony typically consists of 4-8 related 

beavers, which resist additions or outsiders. However, 

close kinship is not a strict requirement for colony 

membership. Recent genetic studies have documented 

unrelated individuals residing in a colony and unrelated 

lactating females sharing the same bank dens. Young 

beavers are frequently displaced from the colony shortly 

after they become sexually mature, at about 2 years old; 

however, dispersal age and patterns vary. Some beavers 

disperse in their first year, while others may remain in the 

colony for three years or more. This variation may be 

affected by several ecological factors, including population 

density. Beaver often disperse to another area to start a 

new colony, but some become “solitary hermits” inhabiting 

old abandoned ponds or farm ponds. Individuals not 

associated with family units (i.e., colonies) may be referred 

to as “floaters”.

Food Habits

Beavers require a mixed diet to meet their nutritional 

needs. They are considered “central place foragers” as 

they search in all directions from their lodge/den site to 

forage on plants. Beavers are best known for eating the 

bark, leaves, and twigs of a variety of tree species, but also 

spend a considerable amount of time consuming other 

plant materials, such as corn, sorghum, soybeans, vines, 

shrubs, grasses, forbs, and aquatic vegetation. 

The size and species of trees cut by beaver are highly 

variable—from a <2.5cm (1 in) diameter at breast height 

(DBH) softwood to a 1.8 m (6 ft) DBH hardwood. Beavers 

sometimes girdle larger trees without felling them. Some 

tree species, such as sweetgum, which ooze storax (a type 

of resin) when girdled, may provide compounds necessary 

for the formation of castoreum. Castoreum is used for 

scent marking. 

U.S. Department of Agriculture Page 15
Food selection may vary greatly by availability, season, and 

region. Beavers forage on aspen and willow (Figure 21)

where available, but will eat a variety of species including, 

but not limited to alder, ash, beech, birch, cherry, 

cottonwood, hornbeam, maple, oak, salmonberry, and 

sweetgum. Beavers also eat conifers like spruces, firs, red 

cedars, and pines. Select parts of conifers are more readily 

eaten in late winter and spring which may coincide with 

rejuvenated sugar flow through the trees. Trees with large 

quantities of phenolic compounds, like red maple, are 

usually avoided, but will be consumed if other tree species 

are not present. Beavers become more selective the 

further they venture from the lodge, selecting smaller 

specimens and more preferred species. Beavers tend to 

select smaller diameter trees of non-preferred species, 

while foraging on all size classes of more preferred 

species. In agricultural areas, beavers will eat crops, often 

traveling 90 meters (98 yards) or more from a pond or 

stream to find corn, soybean, and other growing crops. 

They cut the plants off at ground level and drag them back 

to the water. They eat parts of these plants and often use 

the remainder as dam construction material. 

The legal status of beavers varies from state to state. In 

some states, the beaver is protected except during 

furbearer seasons. In others, it is classified as a pest and 

may be taken year-round when causing damage. Because 

of their aesthetic, recreational, and ecological values, 

beavers are generally not considered a pest until damage 

exceeds a landowner’s tolerance level. Low fur prices for 

beaver in some states have made trapping for profit 

uneconomical. In some northern states, trapping is 

prohibited near lodges or bank dens to protect and 

perpetuate beaver colonies. Fur prices for beaver pelts are 

historically higher in these areas. 

Page 16 WDM Technical Series—Beavers

Figure 21. Fresh willow cutting by beavers.

Legal Status
Castoreum: A secretion that is deposited by beaver on 

mud mounds to mark territorial boundaries.

Crepuscular: Primarily active at twilight (i.e., the period 

immediately after dawn and before dusk) 

Floater: A lone beaver not associated with a family unit or 

colony. 

Flow Device: A tool that combines exclusion and deception 

to maintain positive water flow where beavers dam culverts 

and streams. 

Girdling: The complete removal of a strip of bark from 

around the entire circumference of a branch or trunk of a 

woody plant.

Herbivorous: Eats only plants

 

U.S. Department of Agriculture Page 17

Figures 1, 2, 3, 4, 5, 13, 14, 16, 19 and 21. Photos by USDA-APHIS-WS

Figure 6. Diagram by M. Callahan

Figure 7. Diagram by Jim Miller and Greg Yarrow

Figures 8 and 9. Diagrams by Jim Miller

Figure 10. Photo by Stephen Vantassel

Figure 11. Photo by Dallas Virchow, USDA-APHIS-WS

Figure 12 and 15. Diagrams by Bob Noonan

Figure 17. Diagram by Jill Sack Johnson 

Figure 18. Map from Schwartz and Schwartz (1981)

Figure 20. Diagram from Schwartz and Schwartz (1981)

Acknowledgements

Glossary

Wildlife can threaten the health and safety of you and 

others in the area. Use of damage prevention and control 

methods also may pose risks to humans, pets, livestock, 

other non-target animals, and the environment. Be aware 

of the risks and take steps to reduce or eliminate those 

risks. 

Some methods mentioned in this document may not be 

legal, permitted, or appropriate in your area. Read and 

follow all pesticide label recommendations and local 

requirements. Check with personnel from your state 

wildlife agency and local officials to determine if methods 

are acceptable and allowed. 

Mention of any products, trademarks, or brand names 

does not constitute endorsement, nor does omission 

constitute criticism. 

Disclaimer

Citation

Taylor, J.D., Yarrow, G.K., and J.E. Miller. 2017. Beavers. 

Wildlife Damage Management Technical Series. USDA, 

APHIS, WS National Wildlife Research Center. Ft. Collins, 

Colorado. 21p.

Key Words

Beaver, Castor canadensis, Culverts, Dams, Flooding, Flow 

devices, Gnawing, Roads, Trapping, Trees
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Page 20 WDM Technical Series—Beavers
Damage Management Methods for Beavers

Page 21

Appendix 

 

Type of Control 

 

 

Available Management Options 

 

Exclusion To protect trees from gnawing, total exclusion with fencing (e.g., chain link) is the only proven 

technique. However, this technique is often cost prohibitive. Wrapping individual trees with wire 

(e.g., hog wire or wire hardware cloth) and T-posts can reduce or delay gnawing; however, 

beavers can chew through wire. Seedling tubes are ineffective for protecting individual 

seedlings from beavers. 

To reduce flooding, fencing may be placed upstream of culverts to exclude beavers from 

damming culvert intakes. Culvert fencing is most effective when combined with corrugated pipe 

to create a flow device (see Habitat Modification). 

Frightening Devices Commercial frightening devices are available, but typically do not deter beavers.

Habitat Modification Flow devices are tools that combine exclusion and deception to maintain positive water flow 

where beavers dam culverts and streams. Flow devices are often most effective at dams or 

culverts when corrugated pipe is used in conjunction with an exclusion fence.

Breaching dams may provide immediate relief, but it does not prevent rebuilding and is not a 

long-term solution. Common methods used to reduce or remove dams include mechanical, 

explosive, and high pressure water pumps.

Repellents Repellents are not effective at altering damming/flooding behavior, but some have been shown 

to temporarily affect food selection in some cases. Among these are herbivore repellents, 

textural repellents, unpalatable plant compounds, and predator odors. 

Shooting Shooting may provide very short-term immediate relief (where legal), but like trapping, it does not 

prevent reinvasion. 

Toxicants None available

Trapping Trapping reduces immediate impacts but does not prevent reinvasion. It is an effective method 

for controlling beaver damage as part of a long-term integrated strategy. Consult state and local 

regulations first as they vary on acceptable trap types, trap check requirements, and season. 

Bodygrip traps are a common and effective method for lethal trapping of beaver. Foothold traps 

(longspring and coil-spring types with equivalent jaw spread and impact) may be used for lethal 

trapping of beaver in submersion sets.

“Suitcase” style traps are primarily used for live trapping in dry sets or on the waters edge, but 

can be used as a lethal tool in submersion sets. These traps may also be useful to capture 

beavers for research studies or where state regulations restrict lethal trapping. 

Walk-in cage traps also are used for live trapping and can be used on land sets. Like “suitcase” 

traps, they may also be useful to capture beavers for research studies or where state regulations 

restrict lethal trapping. A relatively new cage trap, commonly referred to as the Comstock beaver 

trap, can be used as a walk-in or swim-in trap. 

Non-powered cable devices (commonly referred to as snares) can be useful, particularly in 

submersion sets and can also be used for live restraint.

Other Methods Electric barriers have been used to deter beavers from entering culverts; however, the 

overwhelming risks to humans and non-target species should carefully be considered before 

using this method.