Controlling BeaversSubmitted by Joe Kambietz.
The beaver (castor canadensis) is a native of North America. The craze for beaver fur hats in the 1700's was the driving force behind the early exploration of Canada. The trapping caused a dramatic nation-wide decline in the beaver populations. However, since then changing land use practices have provided new habitat and caused a surprising rebound in populations of beaver. Clearing of forests for agriculture and logging have given rise to a new succession of light-loving pioneer species such as aspen, birch, poplar and willow, all of which happen to be the beaver's favourite foods. The deepening and channeling of urban stream to enhance drainage has helped beaver, plus urban living has eliminated most of its natural predators. Now this dam building rodent is thriving once again and coming into conflict with landowners.
When dealing with beavers and the problems they can cause we really have only two choices. You can share your property with the visitors or you can take steps to remove them. Overall, an understanding of why beaver do what they do is important to the successful outcome of whichever option you choose.
Beavers are most comfortable in the water since they are clumsy and vulnerable on land. They will build dams to create pools to live in and they will not stray far from shore in search of forage or food. The beaver instinctively builds its lodge in a deep section of the pond or tunnels into the bank to create a den as a home. This reduces exposure to predators and provides a safe place to raise a family. The beaver has three basic requirements in choosing a home site. It needs trees for food and building materials, it needs running water, and it needs the right topography for the dam to hold back water to form a pond.
Before we look at the destruction beavers can cause we should also know that beaver ponds sometimes do good and play an important role in our ecosystem by creating habitat for many animals, birds and insects. In fact, beaver ponds are like a magnet for other wildlife and are one of the best places to observe nature.
Beaver ponds act as a reservoir to impound and store water, therefore reducing flooding events further down stream. This stored water is released slowly and provides for a moderate flow in dry periods that will keep the fish in the creek alive. Coho, cutthroat and steelhead benefit greatly from having the extra habitat, the constant flow and the insect food production from beaver dams.
The beaver becomes a nuisance when they interfere with man's use of the land. Dams can flood large areas of agricultural land or forest, roads can be washed out and cultivated trees and shrubs may be damaged or destroyed. Fish populations in the stream can also suffer if the upstream and downstream travel of the migratory fish is blocked.
Understanding the beaver and their needs will give you a successful strategy for living with them or removing them.
GUIDANCE AND APPROVAL
Controlling beavers or destroying their habitat on private, municipal or crown land is complicated greatly by the fact that the beaver is protected under provincial and federal law, as a fur-bearing animal. Also, the breaching of a beaver dam and the subsequent release of a large volume of water, silt and debris may violate the Canadian Fisheries Act and the Provincial Water Act. Before taking any action to solve your beaver problem on your property, you are obliged by common law to take appropriate care to ensure that your activities will not cause any damage to your neighbour's property. Next find out if the area with the problem beaver has a registered trap line. These people may come and take care of the problem for you, free or for a small fee. To do this contact the regional Provincial Ministry of Water, Land and Air Protection manager and ask if you are in a territory covered by the trapper. If it is not, ask how to get a permit for beaver removal, dam removal or both. There is little value in removing a dam without first managing the beaver population in the immediate area.
Questions to consider:
- What's the name of the stream?
- Where does it flow?
- How large is this stream?
- What is the magnitude of the beaver problem?
- How long is the dam?
- How high is the dam?
- How long has it existed?
- How many beavers occupy the site?
- Are there migrating salmon involved, etc?
All this information is helpful in issuing a permit. Some other important information to think about is;
- What is your strategy to solve the problem?
- Is it a simple fish passage problem that a two-day break in the dam will solve?
- Are the beavers to be live trapped and moved?
- Are the beavers to be killed?
- Do you want the dam removed?
Have in hand a plan before you ask for a permit.
Your key contacts in the approval process are the Provincial Ministry of Water, Land and Air Protection. The Provincial Ministry of Water, Land and Air Protection department handles nuisance wildlife calls, they issue trapping licenses and regulate hunting etc. The Land and Water BC Inc. Department issues permits to work in and about a stream and will have some concerns if the dam is impounding a lot of water, silt and is made from a large volume of trees, sticks mud and logs that could travel down the creek. Fisheries and Oceans Canada is responsible for migrating fish and their freshwater habitat. If there are fish in the stream, Fisheries should be advised of your plans. Lastly, the municipality or City should be contacted with your work plans.
There is a working relationship with these four groups and by contacting one you should be able to get an idea of the complexity of your request and given a contact in the other agencies that will help speed any further permits or permissions.
EFFORT AND SAFETY
Beaver problems occur all times of the year. The two times a year when it is most noticeable are in the late spring and fall. In late spring the two-year-old beaver in the lodge will set off to find their own territory. This is when they might travel, stop at your property and you first take notice of them and their work. The fall is the time of greatest activity for beavers. The dam is strengthened and food is cut and stored for the winter, all during a time of rising water levels.
The best time to deal with beaver dam problems is in July, August and September. There are three reasons for this. First, this is the yearly window of opportunity to do instream habitat work. You will find it much easier to get permission to do the job than at any other time of the year. Second, this is generally the lowest flow the creek will have throughout the year. This makes the release of water, debris, etc much easier to work with. Third, August is a warm weather month and it is much better to deal with a formidable task in the summer then on sleet driven November days.
The work is wet, muddy and slippery and can be exhausting. Like all instream work, it is very easy to over-extend or strain yourself. Take your time and have lots of help to share the workload. Like all other instream jobs have a plan before you start. Carry water and food for frequent breaks and do not forget the first aid kit and a cell phone with emergency numbers at hand. Lastly, because a beaver's dam collects all the debris that floats down the creek, be on the lookout for dangerous garbage. This can be containers of pesticides, poisons, gases and even hypodermic needles. Keep your eyes open and warn any young people you have helping about handling anything that looks out of place. Have all your permit approvals in place before works begins. Allow plenty of time (up to 6 months) to get all the permits.
MATERIAL AND EOUIPMENT
Beaver dam work on a remedial level is fairly low tech. Work involves a rope, shovels, Swede saws, buckets, boots and perhaps a wheelbarrow Bulldozers and explosives should not even be contemplated. Even though these have been used to assist removing dams, a project of this magnitude is beyond this fact sheet and should not be attempted by anyone except a trained professional.
Below are several strategies that will help you solve your beaver problems. These are listed from the simple to more complex plans. It is possible your solution maybe a combination of these. Beavers require three things, flowing water, food and dam building material. If you interfere with any of these things the beaver will abandon the site and move on.
WAIT THEM OUT
In many situations leaving them alone and enjoying the natural cycle of a beaver pond is all you have to do. The beavers will eventually eat all the food available to them and leave. Usually a beaver will not regularly travel more then 50 metres from the water for food, so let this be a rough guide in assessing whether you choose to sit and wait. Certainly, if the beavers do eat themselves out of house and home they will go away. This will leave your property unattractive to any other beaver that may come along in the future.
You may want to speed up the process or protect selected trees by fencing. Use square wire mesh of less then 15 centimetres and about 75-100 centimetres high. Build the fence high enough up the bank so that it will not be flooded over. Fences generally will not last long if exposed to the drifting debris in the pond. The fence must be secure and maintained. If beaver enter through a hole they may fall a tree across the fence to gain further access. Individual trees can be given protection by wrapping their trunks tightly with two wraps of chicken wire 75 - 100 cm wide. This stops the beaver from gnawing at the trunk. By reducing access to forge and building materials you have limited the beavers' ability to stay on your property.
The job of the beaver pipe is to "mysteriously" lower the water held behind the beaver dam. The beaver needs this water to feel secure. If they lose the ability to store water and control its depth they will abandon the site.
The straightforward approach by most people is to destroy the dam to eliminate the pond. This will work if you have a month or so to spare and you can work 24 hours a day, 7 days a week. If you can not, then beavers will repair the dam every night you rest. The secret is not to get into frustrating head-to-head confrontation. If the water drains out of the pond and the beaver can not figure out why, you win!
Beavers are mostly concerned with maintaining the dam face. A beaver pipe is installed through the dam. The inlet must be well upstream of the dam (10-20 metres) and be held well off the bottom by supporting legs. This pipe must be large enough to take the entire flow of the inlet creek; otherwise the pond will not drain. The inlet can not be an open pipe because the beaver will sense the flow and try to plug it. A cap must be put over the inlet end. Outgoing flow is achieved by making hundreds of saw cuts all around the pipe for at least three metres to allow the water to get into the pipe but give no definite place where a significant flow can be felt. Keeping this pipe at least 50-75 cm off the bottom should keep leaves and debris from plugging it. It should still be regularly checked and cleaned. The outlet end should be placed as far downstream as practically possible. Beavers are attracted to the sound of running water and if they can hear the water they may try to plug it on the downstream end.
When the pond water drops and the beaver can not discover why, they will get discouraged and move on, leaving a small pond. New beavers may move in but if the pipe is maintained they will not stay.
If upstream migration of salmon is the only problem there is a fairly straightforward approach. Salmon generally will not migrate upstream without the benefit of an increase in flow from heavy rains. Monitor the dam and look for fish being held up. When fish arrive, simply break a hole in the dam in one place in the evening and let the fish migrate through. The beavers will repair it over-night but most of the fish should have moved through. If more fish arrive, just repeat the process.
In most cases the beaver dams were built to hold back low summer flow. Quite often they are over-topped or broken by the fall and winter rains. In this case only the early fish have to be saved by this tactic. Following are some techniques that may help in making this dam breaching a success. These three simple things need to be done to the dam before the fish arrive.
Firstly, the cross section of a beaver dam will show that it's generally not very high and the base is quite wide. This means that water that does flow over the dam or through the breach you create has an incline to flow down before it reaches the streambed. Fish approaching the flow you create could certainly jump high enough to clear the top of the dam however the broad base of the dam stops them from approaching directly under the flow. Hence many fish that try to leap over the dam by jumping at the water flow of the beaver dam don't make it and drop back and are caught in the branches, sticks and logs that form the dam.
Secondly, a short channel has to be cleared at the back and into the dam to allow the salmon to approach the spilling water from underneath the falls. This allows the salmon to jump up and over easily. Thirdly, a few sandbags may be used at the downstream end of this channel to block the flow. This creates a small pool. The height that salmon can leap is directly related to the depth of the water it is jumping from. This entire channel should be lined with a polyethylene sheet. If the jumping salmon should miss or jump short it will slide back into the channel and pool easily rather then getting hung up in the branches to die. The beaver should not try to rebuild any of this preliminary work as long as you don't release water. Lastly, when everything is in place and the migrating fish have arrived, pull a hole in the dam releasing a small well defined flow into your lined channel and let them jump over the dam. Yes each night the beaver will plug your hole but it can easily be re-opened each time a new migration of salmon show up.
Generally, downstream migrating young salmon are not held back by a beaver dam. Migrating fry, however, will be stopped from travelling upstream by a dam. Keeping a dam open for upstream fry and trout migration requires a little more work, but it can be done. A breach in the dam is made on the far end, unlike the centre breach made for adult salmon. By allowing a flow to come around the long end of the dam the water will naturally flow at the toe of the dam and back into the creek bed. This is not like the one-meter drop you will find at the centre of the dam. Water flowing around the end will descend slowly down the grade to the creek. With a pick, a shovel and a bit of work a channel can be constructed that will allow juvenile salmon and trout to pass around the dam. The beaver will plug this flow but it can be maintained easily because it is at the far end of the dam and not built and armoured as heavily as the centre part of the dam.
By trapping live and relocating your beaver, you are just giving your problem to someone else. If you release a beaver in suitable habitat, other beavers probably already occupy the area. The established beavers will defend their territory and probably attack and kill the newcomer. In any event, removing beavers will not solve your problem, unless you do it continuously. As long as attractive habitat remains on your property it won't take long for new beaver to move back in.
Trapping of any sort is enhanced by complete dam removal. Sometimes if other factors are not over-powering, this will keep beavers away for awhile. Dam removal in this case is not just breaking it up. It means carrying it away from the site and disposing of the debris so beavers can't reuse the material.
Like trapping it is only a temporary measure unless it is done continuously. There is an added factor of destroying a fur bearing animal with a firearm in an urban area that will give provincial and municipal regulators (the permission people) fits... in any case this is just plain dangerous. You are working in a wet, muddy, slippery environment in the twilight, because beavers are semi-nocturnal and you are risking ricocheting bullets off of the water of a flat beaver pond. Shooting sounds like a quick and easy solution but it cannot be recommended. Only in the most dire of situations and then only by qualified people should it be considered.
Destruction of beaver dams alone is not recommended, as it does nothing to make the area unattractive for beavers. If you destroy the dam without eliminating the beaver they will rebuild, often starting the same day. They will use some new trees for repairs and this may accelerate the damage you were trying to stop in the first place. If you remove the beaver and destroy the dam perhaps other beavers will move into the attractive site. If this is the approach you will take prepare to be vigilant.
When considering removing a dam that has been in place for more then a few years, you should be aware of the potential to violate a number of laws and liabilities. The dam will release a sudden surge of water and silt downstream. This may cause a flood event that you will be held responsible for. For example, the released debris could plug road culverts and the ensuing jams wash out a road. Consult with your approval agencies. Complete removal of a large dam may need you to take extra precautions to ensure public safety and the protection of Fish and Wildlife habitat along with private property that is downstream.
This page courtesy of
The Pacific Streamkeepers Federation
September 18, 2003