Preventing Beaver Problems

Keeping beavers alive and working in our waterways is the best possible watershed restoration strategy, and will require resolution of human/beaver conflicts. This article will explain the most common non-lethal methods for preventing beaver problems. Important concepts are in bold. If you’re in a hurry, just read those.

  1. Your location is the root of your beaver problem. You have beavers because you are in an ecosystem that will support beavers. While incredibly adaptable, beavers prefer slow-moving streams with abundant food and water. Since your location is good for beavers, and they’re always under habitat pressure due to human land uses, they’ll keep coming back to it.
  2. You can’t move the problem. As of March 2016 (and counting), California does not permit live trapping and relocation of beavers. This means you can’t move the problem beavers to somewhere they’d be welcomed, and leaves only two options: kill the beavers, or figure out how to live with them.
  3. You can’t kill the problem. Trapping is very rarely a permanent solution to a beaver conflict. While not incredibly fast breeders like rabbits, adult beavers do have a litter every year of anywhere from two to five kits. At two years old, the kits will out-migrate from their home pond and find new habitat (like your area). Trapping your beavers will not change the nature of your problem—it will only buy some time until the next beaver moves in.
  4. You can solve the problem. By understanding beavers, and taking advantage of a few key features of their behavior patterns, you can use a few simple strategies to solve the beaver problems you have.

Problem: Dams Causing Flooding

Why It Happens:

Dam building is instinctual in beavers wherever there isn’t enough water that they are safe from predators. They will try to capture as much water as possible, working from some basic instincts and within some limitations:

  1. The sound and feel of running water triggers beaver’s dam building instincts. This ensures that if their dam begins leaking, they rush over to fix it and avoid loss of predator protection. Scientists once tested this by placing a portable stereo playing the sound of running water near a beaver colony. The beavers responded by covering the stereo with sticks and mud. Obviously, they can be outsmarted.
  2. Trying to remove the dam is a losing proposition. If you tear down a dam, the beavers will immediately begin rebuilding it. They’re not trying to give you a hard time. They are fighting for their lives, and the lives of their young, driven by fear of predators who will eat them if they don’t have the protection of their pond. In full panic mode, they will work tirelessly until the dam is repaired. Additionally, the silt and muck that wash downstream are bad for stream health, and can suffocate endangered salmonids, especially during spawning season.
  3. Luckily, beavers will stop adding to a dam when more work does not impound more water. Plant matter in general isn’t a very high-energy food source, and beavers have to work really hard just to survive, so they’re not going to waste any energy they don’t have to. If we can control how much water the dam holds, we can keep them from flooding an area we’d rather keep dry. We can take advantage of this instinct by using a pond leveler.

Solution: Pond Leveler

To prevent flooding, use a pond leveler that lets you control how high the water rises in their pond. See the Pond Leveler description below for more information.

Problem: Cutting Trees and Other Vegetation

Why it happens:

Beavers are generalist herbivores, eating a surprisingly broad diet of trees, plants and shrubs as well as aquatic vegetation. They only eat plants, despite the common misconception that they eat fish (otters and muskrat are commonly mistaken for beavers, and they do eat fish).

  1. Beavers cut trees and vegetation for food and building materials. They will also cut more than they eat in order to create a food cache for winter. Since they don’t have chainsaws and felling wedges, sometimes the trees they cut will hang up in the canopy of surrounding trees. They don’t climb, and can’t get to the food and building materials, so they have to go after another one. They’re not trying to cut down the whole forest. And, contrary to popular belief, they don’t “eat themselves out of house and home” and then move on like locusts. They are actually tree farmers, managing a coppice, and practicing crop rotation. Their preferred trees will re-sprout after being eaten, sending up multiple shoots from a single stump. When the beavers return to where they started, which they will after a few years, there’s another crop of trees ready for harvesting. As well as a wider floodplain, higher groundwater table, and a wider riparian corridor—all good things in California’s parched landscape.
  1. Like all rodents, beavers have teeth that never stop growing. If beavers are deprived of materials to wear down their teeth, they will die when the teeth grow back into their head. They have to chew continually to keep them a manageable length, and so will gnaw trees even if they aren’t going to eat them.

Solution: Wrap and fence trees and other vegetaion.

Since beavers don’t climb, you can protect trees by either wrapping them in wire individually, or fencing out an area of multiple trees. Painting trees with a sand/paint mixture has had limited success, but requires frequent maintenance. If aesthetics are a concern, consider a two-strand electric fence instead. See Vegetation Protection below for details.

 

Problem: Blocked Culverts Causing Flooding

Why it happens:

As noted above, beavers want water for protection from predators. In the case of culverts, we’ve done almost all the damming for them. All they have to do is repair a couple small culvert-shaped leaks, and instant pond! No wonder they love the things so much.

  1. Beavers are plenty smart enough to use our infrastructure for their ends. Since they don’t have to do the tedious, dangerous work of felling and dragging enough trees to make a whole dam, a culvert is the ideal place for a beaver to get a new pond fast, by just plugging it up.
  2. Roadways are a much more permanent structure than regular beaver dams. They leak a lot less, require less maintenance, and can often impound incredible quantities of water with less danger of blowing out. Beavers can get by in more marginal areas by damming culverts, thus saving more of their energy for foraging, lodge building and other activities.

Solution: Culvert Protector

Here the answer is to use a culvert fence with a pond leveler running through it. The fence protects the culvert, and the pond leveler keeps the water level where we need it. The Culvert Protector section below has more information about these.

 

POND LEVELERS

Please read this section before requesting a consultation. It will address some common questions and misconceptions.

  1. Beaver “dams” are nothing more than soft, leaky piles of sticks and mud that briefly slow down the flow of water. They don’t actually stop the water, they’re not anchored to anything solid, and they won’t survive high flow events. They are much more akin to sponges than dams, and the water behind them is not trapped. It is merely delayed.
  2. Pond levelers are very simple and lightweight. A pond leveler is a small cage made of fencing, and a short length of flexible pipe installed through the pile of mud and sticks. An experienced person, working alone, can make and install one in 4-5 hours using simple hand tools.
  3. A pond leveler is not a siphon. In fact, these systems are specifically designed to make sure that siphoning is impossible. The entire top of the pipe is perforated, ensuring that no vacuum can form.
  4. So it can’t build any pressure. There is zero “head”, because the inlet for the pipe is below the outlet. The pond leveler simply acts as an overflow for the beaver dam, no differently than an open spillway.
  5. Therefore no concrete or engineering is required. During high flow events that briefly overwhelm the overflow’s capacity, the beaver “dam” it is installed through will be first overtopped, and then washed downstream entirely if flows are high enough.
  6. And it can’t drain the area. The installer and landowner determine the final water height, which should keep as much water as possible in the pond. This allows the beavers to stay in the area, prevents flooding, and retains valuable habitat for all the other species that depend on the beaver ponds.

 Vegetation Protection

Done correctly, vegetation protection work will last a long time and work well. It’s simple, cost-effective, and can be visually unobtrusive.

  1. Painting trees is a good option for areas with aesthetic concerns. Go with fencing when you can, as it lasts quite a long time. However, if aesthetic concerns rule out fencing, it is easy to color-match the bark on tree trunks for a nearly invisible treatment. The sand/paint mixture needs to be re-applied and checked regularly—6 months to a year depending on climate. Luckily, it’s quite cheap and easy to do.
  2. All fencing must extend 3’ above the anticipated snow level. Legends of ten-foot tall beavers are not uncommon, especially in areas that get ten feet of snow… So if you’re walking through a forest and see beaver chews at head height, that’s what happened. If you get snow in your area, it’s critical to wrap or fence your trees high enough that beavers can’t get to them when standing upright on the maximum snow height you expect for the season. And checking as the season continues is required for success.
  3. If wrapping trees, use heavy wire with a small mesh and be sure to leave room for the trees to grow (no chicken wire). Wrapping trees too tightly will girdle and possible kill the trees, and mesh that’s too large will allow young beavers to wriggle through and nibble the trunks.
  4. If you have multiple trees to protect, consider fencing an area rather than individuals. This is faster, easier and more efficient while offering the same protection. Be aware that riparian corridors are vital pathways for wildlife, so be sure your fenced areas have gaps between them that wildlife can navigate.
  5. Only wrap trees you’re really attached to or that present a threat if felled. Beavers are supreme ecosystem engineers, and given a few years can radically transform degraded habitat. Many trees that beavers prefer will re-sprout from the base when cut down, thus creating many more trees than were there before. Patience is key—what looks like a clear-cut this year will be a lush garden in a few seasons, and provide quality habitat for a radical increase in biodiversity. If you’re interested in doing the most good, give the beavers all the trees you can.

 

CULVERT PROTECTORS

Done right, a culvert protector should be a very low maintenance solution to culverts that are being blocked by beavers. They are robust, inexpensive and can offer additional protection against storm flows that might otherwise block culverts with debris.

  1. Culvert protectors are simple, sturdy, and easy to install. Each consists of a fence protecting an area in front of the culvert, a pipe that runs through the fence into the culvert, and a cage on the end of the pipe in deep water. An experienced person, working alone, can make and install one in 5—6 hours using simple hand tools.
  2. A culvert protector is not a siphon. These systems are specifically designed to make sure that siphoning is impossible. The entire top of the pipe is perforated, ensuring that no vacuum can form.
  3. So it can’t build any pressure. There is zero “head”, because the inlet for the pipe is below the outlet. The culvert protector simply ensures that beavers can’t block the culvert, and keeps the water moving.
  4. And no additional concrete or engineering is required. A culvert protector acts somewhat like a trash rack, and helps keep the culverts flowing. It doesn’t add any additional water, nor does it present a threat to the existing infrastructure.
  5. They’re low-cost, fail-soft insurance. In some extreme high-flow events (think hurricanes and 100 year storms), a culvert protector can be crushed, collapse, or be overwhelmed by the flow of debris and water generated by a storm. In a storm event of this magnitude, the culverts themselves will also be overwhelmed, as will the road surfaces and other local infrastructure. A culvert protector cannot augment the flow of undersized culverts. What it can do is keep the culvert open and running longer than it would otherwise. In some cases, a culvert protector can even save the road before it fails. Think of it as an additional layer of protection for the culvert and roadway.