Controlling Beaver Damage
The Unwelcome Visitor
The water is rising in the basement and flooding the driveway, and as you inspect the back creek, you come across a pile of sticks, a neatly packed dam, and the SLAP of a beaver tail. Now what are you going to do? You have a beaver problem, but who do you call for help?
Contact your DEC Regional office. DEC staff can offer information and technical guidance on how landowners can deal with beaver problems.
First and foremost, the Bureau of Wildlife serves the public by managing the size of the beaver population. Without management, beaver populations grow too large. A pair of beaver and their offspring can produce up to 600 offspring over their 10-year reproductive life. With proper management, however, they provide great benefits to all the people of New York.
Management in the case of beaver translates to annual harvest by licensed trappers during an open season. By varying the length of the open season we can vary the number of beavers taken and consequently the size of next year's population. [The season is open from mid-December to late March in most of New York State. Check the trapping regulations guide for exact dates in your area.]
The Management Process--WMU's
Biologists have divided the State into ecologically-based Wildlife Management Units (WMU's). For each WMU, a beaver population management objective has been set. These objectives are the result of careful analysis of beaver biology, habitat quality, human land use, and public tolerance levels. Objectives vary from a 10% to 30% occupancy rate in our region. In other words, wildlife managers would like to see beavers in 10% to 30% of the places where beavers could live.
Setting the management objectives is the most important beaver management decision. But, we don't stop there. Biologists also measure whether these objectives are successfully being met. Each year DEC monitors the beaver harvest in two ways - first by requiring New York trappers to report every beaver they take, and secondly by conducting telephone surveys to refine these figures.
But, measuring the annual harvest doesn't always tell us exactly how many beavers are out there. There are natural variations in populations, too. So, to annually re-assess the population size, trained observers conduct aerial surveys to count colonies.
The Right Number
All of these activities (WMU mapping, objective setting, harvest assessment, and population surveys) are designed to arrive at a population that will afford the people of New York the opportunity to enjoy all the benefits of beavers without suffering the problems that beavers can also cause.
The True Problem Solvers
But that's not all there is to beaver problem solving. There is another important step, namely trapping. It is the biologist-trapper partnership that makes beaver management work, and it's the trappers, themselves, who are the problem-solvers.
It's the trapper who will solve your problem. But, the DEC can play matchmaker; joining problem with solution. We can give you a list of trappers and/or trapper's organizations that you may contact to get help. We can also give your name to experienced trappers so they might contact you for permission to trap your land.
The biologist-trapper partnership is undoubtedly the best long term solution for beaver management in New York, but there are times when it does not provide relief as fast as some would like. There will always be cases where beaver problems need immediate attention, even if the season is closed. In these cases, a landowner can apply for a Wildlife Damage Permit by calling the DEC Regional Office. Wildlife staff may visit your site to assess the situation and offer solutions.
This may even involve authorization for you or an agent to take beaver out-of-season. Unfortunately, during the summer and fall, the beaver pelt is of little value due to natural seasonal pelage changes and the pelt cannot be sold. So, taking out-of-season beavers under permit is a poor way to reduce the population because it decreases one of the important values of beavers. Many times the best solution is to wait until the season opens.
Those Tricky Dams
Often beaver problems aren't with the beaver as much as the dam. Many landowners would like to have beavers if only they wouldn't raise the water so high. State regulations require that you must consult with the DEC Bureau of Wildlife before you do anything to a beaver's dam. A permit will have to be issued. This permit process allows us to provide important advice about dams and beavers. The management of beaver's dams, you see, is just as important as the management of beaver.
Beavers build dams to increase the size of their habitat. They gain access to more food as the pond gets bigger. Some measure of protection from predators is also provided.
The sound of running water triggers beaver activity. If there is a leak in the dam, you can be sure beaver will work through the night cutting more trees and hauling more mud to patch it up. It is for this reason that we recommend against disturbing the dam. The end result is always more disturbance to the area's trees and a likely increase in water levels.
In some situations, there are methods to quietly leak the water through the dam, without arousing the beaver. Wildlife professionals can give you advice on construction of these devices, and the required permit for disturbance to the dam. These devices are not maintenance free, however, and they can prove expensive in both materials and time.
The Good News is...
With all this talk about beaver problems, one might think that that's all beavers do is create problems. Really, that couldn't be further from the truth. In fact, they can be credited with inexpensively creating valuable wildlife habitats.
Let Us Help
So, we hope all your encounters with beavers will be pleasant ones. We do think our Official State Mammal is quite a wonder to behold. More times than not, beavers and man can co-exist. But if you should have a problem, give us a call, and we'll find some way or someone to help.
For more information about beavers and beaver regulations, contact the New York State Department of Environmental Conservation's Bureau of Wildlife at the Regional Office near you.
The Biology and Behavior of the North American Beaver(Castor canadensis)
The beaver is the largest rodent in North America with adults ranging from 35 to 46 inches long (including a flattened 12-18 inch tail) and weighing from 45 to 60 pounds. Beavers weighing over 100 pounds have been recorded. The hind feet are very large with 5 long webbed toes. Front feet are small and dexterous, which allows the beaver to carry dam construction material such as stones and sticks.
Both sexes of beaver breed at 21 months of age from December through February. Females ovulate 2 to 4 times at 7 to 15 day intervals during each midwinter breeding season. There are no records of beaver breeding as first year kits. Development of the fetuses requires 120 days with the young being born between April and July Litter sizes range from 1 to 9 with an average litter size of 4. The heavier the female, the larger her litter, also the number of young a female bears is inversely related to her family size at the time of breeding. Adult females will breed every year regardless of the habitat quality.
The occupants of a beaver pond or group of ponds is a family consisting of two adults and their offspring of two breeding seasons. Beavers mate for life; however, if one of the adult breeding pair is removed from the population, the remaining member will readily accept a new mate. The kits remain with the parents until they are 2 years old and then are driven off to find their own territories. This dispersal of juveniles can contribute greatly to the total number of property damage complaints.
As a food source, beavers prefer aspens and willows but will eat the leaves, twigs and bark of most species of woody plants found along the water's edge. During the growing season beavers will also consume large quantities of non-woody plants such as grasses and cattails. During the fall, they will stockpile their woody food supply in the water near their house for use during the winter months. The presence of these fresh cut feed piles is an important indicator of an active beaver lodge. During the ice covered winter months beavers are generally inactive with regard to tree cutting and dam building.
Beavers construct dams which result in the formation of ponds within which the lodge and winter food cache are located. It is believed to be a combination of water flow sensation and the sound associated with running water that stimulates this dam building activity. Within and around the pond the beaver construct canals for security and for the transport of food and building materials. Beavers are primarily active at night with regard to their dam building and tree cutting activity.
The beaver's dam and lodge are constructed of sticks and mud, with some beavers utilizing bank burrows along streams or ponds. Lodges consist of one or more compartments with each compartment having two underwater openings for exit or entry These are also important for escape from potential predators. Their aquatic habitat and instinctive behavior minimizes the adult beaver's susceptibility to predators. Domestic dogs, coyotes, bears and bobcats are among the larger predators in New York State that will prey on beaver if the opportunity arises. However, since beaver rarely travel far from water, they are relatively safe from most predators. Young beaver are more susceptible, with predaceous mammals such as otter and mink occasionally preying on kits. Overall, natural predation probably has little effect on beaver populations in New York State.
The impoundments created by beavers provide valuable wildlife habitat for assorted furbearer and waterfowl species. In this way, the beaver provides valuable ecological benefits to the public at large. On the other hand, the beaver's dam building activity can result in widespread flooding of woodlands and agricultural land and cause numerous complaints by plugging road culverts, flooding roads, railroad tracks and causing general property damage concerns.
This device prevents beavers from building a dam inside a culvert. This is a preventive measure and not a water regulation device. If beavers build a dam in front of the culvert, other measures should be taken.
- 1/2" -3/4" metal rods spaced 6" apart and held together only at the top with horizontal rods.
- Held in place by the current and by driving the vertical rods into the bottom.
- Easier to remove than wire mesh because there are no horizontal bars to catch on deposited material.
For more information, see the publication Managing Nuisance Beaver Along Roadsides (PDF) (250 kB).