The Future of Responsible Beaver Management

Why We Should Protect Wisconsin’s Beavers

"When we try to pick out anything by itself, we find it hitched to everything else in the Universe." This oft-quoted phrase, written by John Muir in 1911, is particularly applicable to beavers today. When one species –beavers– are removed from the environment, there can be far-reaching negative consequences. Whole ecosystems teeming with wildlife can be destroyed, along with the important free services beavers provide our communities. 

Beavers are ecosystem engineers
The much-maligned American beaver (Castor canadensis) is a medium-sized, semi-aquatic mammal of the rodent family whose size and reputation belies its powerful role as an ecosystem engineer. These industrious, 40-pound creatures build highly complex wetland ecosystems as homes for themselves and their families, and in doing so, they create habitat for the 75% of Wisconsin’s wildlife that spend all, or part of, their life cycle in wetlands - including 32% of all Wisconsin’s threatened and endangered species. Protecting beavers, a keystone species, is thus vital to maintaining healthy wetland ecosystems in Wisconsin.

Beavers create complex wetland habitats
Beavers initiate an ecosystem engineering project by building a single, primary dam on a stream, which backs up water and creates a pond. They may also build smaller secondary dams that create additional ponds. Beavers are slow and awkward on land and prefer to stay in the water to avoid predators like bears and wolves. These enterprising creatures build an intricate system of canals from their ponds leading into the forest to access their primary food source – trees, while remaining in or near the water. Over time, this colonized portion of the stream becomes a large wetland complex consisting of ponds and braided meandering channels that effectively spreads and holds water on the landscape and supports a thriving community of streamside vegetation.

This intricate wetland water world creates a mosaic of habitats that serve as homes and feeding areas for many hundreds of species, from the smallest macroinvertebrates to fish, birds, waterfowl, and large mammals. A wetland complex such as this serves as a critical refuge for wildlife and plants during times of drought, a warming climate, and wildfires.

Beaver wetland complexes benefit trout
Some incorrectly believe that beaver dams block fish movement. This is not true of dams in mature beaver wetland complexes. Beavers build dams that are inherently “leaky.” Fish and amphibians easily move over, under, and through the dam structure, or they bypass the dam altogether using side channels for movement upstream and downstream. Beavers and trout have shared a long history of coexistence, with both species thriving for millennia in the absence of human management. Beaver ponds provide trout with a place to rest, an abundant supply of aquatic insects, cool water in the summer, and deep pools for winter refuge.

Routinely removing beavers and beaver dams from trout streams to improve fish passage is ill-advised, and temporarily interrupts fish movement. A newly constructed dam needs time to evolve and reconnect the stream with the floodplain to avoid the potential interruption of fish passage. As the water volume increases behind the dam, connecting the stream to the floodplain, fish can once again move easily over, under, through, and around the dam.
 

Beavers provide free benefits for people
A peer-reviewed study published in Mammal Review in October 2020, calculates that beaver ecosystem services, including the following, are valued at $179,000 per square mile every year.

• Increased Water Retention: A mature beaver-created wetland ecosystem holds millions of gallons of water on the landscape -- approximately 1 million gallons of water per acre. The surface water in the wetland complex is, however, small compared to the amount of water held in adjacent soil, gravel, sand, and rock as groundwater. Beavers’ structures slow the flow of surface water, which significantly contributes to groundwater recharge. It is not inconsequential that in Wisconsin, 70% of residents and 97% of communities rely on groundwater as their drinking water source.
• Flood Control: Beaver wetland complexes slow the rate of flashy stream flows from major rain events, protecting downstream riverbanks and infrastructure from erosion and collapse. Beaver structures attenuate downstream flooding by as much as 60%, protecting roads, homes, farms, and businesses from flood damage. 
• Sediment Capture: Wetlands clean stream water. As rain and surface water runoff moves through a wetland, chemicals like nitrates, phosphates, and sodium chloride (road salt) are removed. Silt settles out behind the beavers’ dams, preventing it from moving downstream and clogging gravel spawning beds. 
• Carbon Sequestration: A wetland ecosystem sequesters significantly more carbon than a comparably sized forest due to the relatively slow decomposition rate of wetland soils. 

It takes a decade or more for a single beaver dam to mature into a complex, fully functional wetland ecosystem that delivers the myriad of important services that beavers provide, but it takes just a few hours and a couple sticks of dynamite to destroy it. Many years may then pass before beavers return to a damaged wetland ecosystem to begin the process of restoring it

Short History of Beavers in Wisconsin
Historically, beavers were found in nearly every stream and flowage in Wisconsin. They fulfilled an important role on the landscape by fostering ecological diversity and providing critical habitat for countless other wildlife species. Beginning around 1650, however, Wisconsin's beavers became an important commodity and would remain so for the next 200 years. The fur trade, driven by the demand for beaver felt hats in Europe, decimated the beaver population. A combination of unrestricted trapping, and habitat alteration from more than 50 years of intensive logging and slash burning of Wisconsin’s forests resulted in near extirpation of the State’s once robust beaver population by 1900. The absence of beavers led to a 50% wetland loss in Wisconsin, which has yet to recover.

Settlers arriving in the State located their farms along streams where water was available for their farming operations, and towns sprung up along rivers for access to water and navigation for commerce. Many of these were places where beavers had once flourished. As the remnant beaver population began to rebound slowly and move back to their historic beaver habitats to re-establish their homes, conflict with the new tenants was inevitable.

Beaver trapping was closed in the early years of the 20th century due to their small numbers. In 1917, the State’s first legislation was passed to allow the trapping of “complaint” beavers. There were a small number of beaver complaints registered initially, but by 1945, the number of beavers and complaints had grown substantially. By this time, the extensive areas of forest in the State that had been logged and burned were regrowing a cover of primarily pioneering aspen and birch – food preferred by beavers!
 

Current Beaver Management
Today’s human-built environment – homes, cities, farms, and road infrastructure – exacerbates conflict with beavers. Beavers can plug road culverts and irrigation ditches, flood roads and farm fields, or cut down trees. The Wisconsin Department of Natural Resources (WDNR) developed the State’s first Beaver Management plan in 1990. This plan focused primarily on reducing beaver populations to protect critical resources. The successor plan, the Wisconsin Beaver Management Plan 2015-2025 (the Plan) continues to emphasize reducing beaver populations for trout stream protection but also considers the importance of beaver populations and the valuable ecosystem services they provide.

Although the goals of the Plan are legitimate, beavers are treated today as a nuisance species in State policies. There are no harvest limits on beavers during the long trapping season, and landowners may kill beavers and remove dams on their property without a permit at any time of the year (NR 12.10(1)(b)1.c). In fact, landowners may remove beaver dams from their neighbor’s property if they believe they are a nuisance (88.90(3)).

In 1988, the WDNR began contracting with the USDA’s Animal and Plant Health Inspection Services, or APHIS, to lethally manage Wisconsin’s beaver population at an estimated annual cost approaching $500,000 in some years. In 2023, according to USDA-APHIS-Wildlife Services, beavers and their dams were removed from 1,800 miles of trout stream, and 3,132 beavers were killed deliberately, along with 148 otters killed accidentally.

Simply killing beavers in a conflict situation completely ignores the significant benefits that beavers provide our communities. The U.S. Fish and Wildlife Service notes that beavers are “one of the most cost effective and sustainable solutions for ecological restoration and climate change resilience.”  A new approach to beaver management is needed. Current non-lethal beaver management techniques need to be employed to mitigate conflicts wherever possible, and most importantly, more research is indicated – particularly regarding beaver/trout/watershed interactions – to inform policy reforms as Wisconsin moves forward to update its beaver management plan.

The Future is Non-lethal Beaver Management
It is a beaver’s instinct to dam flowing water. Researchers have demonstrated that both in the wild and in captivity, beavers will build a dam around a speaker playing a recording of the sound of running water. This instinct serves them well in keeping their dams in good repair, but it causes a problem when their dam plugs a culvert or floods a farm field.

There are various types of inexpensive, easily fabricated, and effective flow devices designed for protecting culverts or for lowering the level of a pond to prevent flooding. These coexistence tools, when properly deployed, can usually resolve flooding problems. Simply killing the beavers and removing their dam is not a long-term solution, because if it’s a good place for a dam, new beavers will invariably move in and recolonize the area.

Experience over the past 20 years has shown that the cost of killing the beaver and removing the dam is typically twice the cost of installing a flow device. Beaver and dam removal is, at best, a short-term “fix” that must be repeated regularly. A properly designed and constructed exclusion device is a relatively long-term solution, yielding annual economic benefit. Coexisting with beavers saves money and keeps the creatures on the landscape to continue providing valuable ecosystem services for the community. Non-lethal beaver management is clearly the preferred approach from both an ecological and economic perspective.

Read about coexistence tools on the Illinois Beaver Alliance Webpage: Examples of Flow Devices | Illinois Beaver Alliance

Beaver Relocation
Sometimes beavers select a location for their home that will not work for people or for the future of the beavers! Beavers have been known to build dams in unlikely places, such as irrigation canals, road ditches, Walmart parking lots, and water treatment facilities. Scenarios such as these call for the relocation of the beavers. The offending creatures can be live trapped and moved to a new location where they are needed. This may sound simple, but it is not. In Wisconsin, beavers can be relocated to private property with the landowner’s permission, but they cannot be relocated onto public property. Finding a suitable place to move a beaver, or a beaver family, can be an impediment to successful relocation. Because of the potential difficulty in finding a place to move beavers, many municipalities contract with APHIS Wildlife Services to simply kill the beavers and remove their dams. Such short-sighted lethal “solutions,” however, often become an annual necessity – and an annual expense.

Several states, acknowledging the increasingly valuable ecosystem services provided by beavers, have instituted policies and programs to facilitate the process of relocating beavers to habitats where their services are needed.  For example, the Wyoming Game and Fish Department (WGF) has a statewide system that identifies places, both on public and private land, where beavers will be an asset, and in some instances, where these rodent engineers have been requested by landowners. WGF recently built a beaver holding facility in Cody to house beavers temporarily until an entire family is trapped and is ready to be relocated. The Department subsequently uses a “beaver trailer” to move them to their new homes. Wyoming is among a rapidly growing number of states that recognize that beavers’ biggest benefit is their ability to store water on the landscape. As our climate continues to warm and our weather patterns change, beavers’ ability to store water, improve water quality, reduce erosion and runoff, and create habitat for a wide range of other wildlife species, becomes ever more important.