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CMMCP Beaver Mitigation Program




The Central Mass. Mosquito Control Project (CMMCP) receives many requests from city and town officials and property owners seeking assistance to alleviate flooding cause by beaver activity.   CMMCP recognizes beavers as keystone species of the natural and ecological landscape.  Beaver activity creates wetland and wildlife habitat that benefits many plant and animal species.  Along with the positive aspects of beaver activity come some negative aspects.  The most frequent issue affecting CMMCP is dam building activity which clogs culverts and drainage ditches.  Increased flooding creates new habitat for mosquitoes and increases the need for Integrated Pest Management (IPM) techniques. 


Proper management of beaver populations is needed to address the negative aspects of beavers.   Health departments have the authority to determine whether a complaint is caused by beaver or muskrat and whether the situation constitutes a threat to public health and/or safety, as defined in the Massachusetts Beaver Law, M.G. L. c. 131, and s. 80A. CMMCP will assist cities and towns with beaver conflicts on a case-by-case basis.


CMMCP supports and follows the recommended practices for beaver management per the Massachusetts Division of Fisheries and Wildlife.  Beaver activity will not be interrupted unless it becomes a threat to public health and safety per the Massachusetts Beaver Law M.G.L. c. 131 S. 80A. CMMCP will fully adhere to the permitting process as regulated by the Division of Fisheries and Wildlife (DFW) and the Department of Public Health (DPH).


CMMCP staff have been actively gaining the necessary licenses and knowledge over the past few years to be able to deliver this new service to member cities and towns. We have attended seminars and workshops to obtain licenses, interact with biologists, trappers and beaver mitigation experts. Click this link for a brochure from a seminar held in 2013 by the Northeastern Mosquito Control Association (NMCA):


Certain restrictions apply to this program, and CMMCP reserves the right to determine a project is not feasible.



Best Management Practices


CMMCP will consider all options for resolving beaver conflict according to the recommendations of the Division of Fisheries & Wildlife (DFW).  CMMCP staff such as the Wetlands Project Coordinator and Wetland Project Specialists will keep current with all beaver control laws including hunting and trapping regulations.

The following website is MassWildife’s Beaver Management home page and may be referred to for current rules and regulations:


CMMCP best management practices for beaver control will be guided by the DFW publication:

The Use of Water Flow Devices in Addressing Flooding Problems Caused by Beaver  This publication is a manual designed as a reference tool for people who are incurring beaver problems. The manual provides the information necessary to determine which technique, if any, is the best option for any particular situation.


CMMCP will utilize the Best Management Practices as set forth in the Massachusetts Best Management Practices and Guidelines for Freshwater Mosquito Control (Draft Version Nov. 1, 2007).


The following Options for Resolving Beaver Conflicts is an excerpt from MassWildlife website and shall be considered:


Options for Resolving Beaver Conflicts:


1.       Tolerance - People who learn to tolerate a certain amount of beaver influence on their land generally find that co-existing with beavers provides more benefits than perceived harm. In situations in which beavers are simply an inconvenience to landowners, tolerance is the easiest solution.


2.       Enclosures - Fencing can provide a long-term solution, while preserving the beneficial aspects of beavers. The most effective way to protect specific trees and shrubs is to construct enclosures around them. These enclosures should be constructed of heavy-gauge fencing, be a minimum of 4 feet tall, and be flush with the ground. To protect larger areas, such as orchards or nurseries, standard fencing is usually sufficient since beavers are poor climbers, rarely burrow under fences, and generally don't chew fencing unless it is wrapped around trees or shrubs. CMMCP does not typically offer this service.


3.       Breaching and removing the dam - Dam breaching is an immediate, but short-term solution to flooding problems caused by beaver. Cued by the sound of escaping water, beavers will usually rebuild the damaged dam quickly, sometimes overnight. If the afflicted landowner does not want beaver lethally removed, it is recommended that a water level control device (WLCD) be installed to prevent beaver from rebuilding the dam. Please see below for further information on WLCDs. Permits are needed to disturb or tear open a beaver dam or beaver lodge for any reason. Dismantling or breaching a dam can result in severe flooding for property adjacent and downstream of the dam. Dam breaching and removal affects wetlands; such activities are regulated by Massachusetts' wetland protection laws. To find out how to obtain a permit, please read our "Beavers and the Law: A Citizen's Guide to Addressing Beaver Complaints" (.pdf).


4.       Water Level Control Devices (WLCD) - In situations in which increased water levels threaten property, crops, or public health and safety, water level control devices (WLCD) may be an appropriate way to control the flooding. Sometime referred to as "beaver pipes" or water flow devices, WLCDs can be successful at regulating water levels at desirable levels behind dams. By successfully installing an effective WLCD, the life of a desirable beaver wetland, and its associated benefits, can be prolonged. An assortment of WLCDs are available and all have advantages and disadvantages associated with their use. Two factors are key to the success of these devices: they must be designed to reduce the cues used by beavers to detect escaping water, and they must be difficult for beavers to plug. Water flow devices should be used only where appropriate conditions exist and will likely require regular maintenance. Do not try to install a water level control device on your own. In Massachusetts, it is illegal to disturb beaver dams or lodges without a permit.


5.       Lethal removal - Beavers can be trapped during the open season (November 1-April 15) by a licensed trapper using permissible traps (i.e. box or cage-type traps). An Emergency Permit is not needed during the regulated season if permissible traps are used by a licensed trapper. By removing beaver during the regulated trapping season, they can be used as a natural resource because its pelt, meat, and castor oil are highly valued and can be used. Trapping is highly regulated in Massachusetts. An Emergency Permit is needed to trap beavers with restricted traps (i.e. body-gripping traps, "conibear" traps) and to trap beaver outside the regulated trapping season. Removal of problem beaver can be a quick way to alleviate beaver problems when done by an experienced trapper. New beaver may move into the area, but this depends on several factors, such as the habitat features and the density of beavers in the area.


It is against state law to capture and release beaver into another area. Often people want to capture problem animals and release them someplace else. However, moving wildlife is detrimental to both people and wildlife populations and is against the law. This law has been in effect for many years, protecting both people and wildlife.


Permitting for Beaver Removal and Beaver Dam Breaching or Installation of a Water Flow Device.


The main remedies for beaver control are trapping beaver, breaching dams or installing water-level control devices (beaver deceivers).  The use of these measures will be assessed on a case-by-case basis by the Wetlands Project Coordinator and recommendations will be discussed with the property owner and town officials.  The most appropriate form of control will be utilized per M.G.L. 131, s. 80A.


Massachusetts Beaver Law:

 M.G.L. c. 131, s. 80 A – An Act relative to Foothold Traps and Certain Other Devices. 

The law grants permitting authority with local Boards of Health in situations were beaver activity is causing threats to human health and safety.  The law also outlines what types of beaver conflicts could constitute a threat to human health and safety, though the local Boards of Health can use their own discretion.


Many state environmental statutes specifically exempt mosquito control work authorized under the provisions of M.G.L. c. 252, including, most notably, M.G.L. c. 131, §40 (Wetlands Protection Act) and M.G.L. c. 40, § 8C, (Conservation Commission Act).   Because of this exemption CMMCP is not required to obtain permits from the Conservation Commission.  However CMMCP will notify the Conservation Commission when modifying a beaver dam (i.e. breaching or installing a flow device).  CMMCP will provide the Commission with a copy of the CMMCP Beaver Management Guidelines.  Any information supplied by the Conservation Commission will be considered when developing a plan for beaver control.


Note:  Massachusetts Department of Environmental Protection (DEP) and the US Army Corps of Engineers (USACE) typically have considered the emergency permit issued by the Board of Health satisfactory for CMMCP to conduct dam removal and have not required any other paperwork.


To initiate a site assessment, please e-mail Wetland Project Coordinator Katrina Proctor at



Water level Control Device (WLCD) examples:



Keystone Culvert Fence:

Trapezoidal Culvert Fence Diagram -  Side View



Flexible Pond Leveler:





Fence & Pipe Flow Device:


Fence and Pipe Diagram - Side View