Wisconsin is home to more than 13,000 miles of trout streams. Each year, the state Department of Natural Resources works on habitat restoration projects to help trout populations thrive, both on public lands and private properties where the state has an easement to allow access to fish.
Wildlife officials say part of that work is keeping another native species from thwarting their efforts: the beaver. However, some conservationists resist the idea that beavers pose a threat to trout populations.
David Rowe is the director of the DNR’s Southwest Wisconsin Fisheries Team. He said beavers are part of the native wildlife along these waterways, but his team’s work in creating the ideal habitat for trout often attracts beavers to the area.
He said the rodents love the shrubs, such as willow and elder, that grow along the streams, and the rocks used to stabilize the banks are an ideal foundation.
“It looks very attractive for a beaver to enclose its dam with a hard spot, and its dam will last longer. So the beavers you know that are going up and down these creeks are like, ‘Oh wait a second great place to build a dam now,'” Rowe said. “So we’re making it more appealing to them. “
He said a beaver building a dam can undo the DNR’s paid-for habitat work on a creek through the $10 trout brands bought by Wisconsin anglers.
In addition to preventing damage, Rowe said the main reason DNR officials are removing beaver dams in his area is the flooding that can occur around the waterway. On public lands, he said, the DNR often allows the dam to remain because recreational trappers help control the beaver population. But on private land, Rowe said, the DNR is working with the US Department of Agriculture’s Wildlife Services to trap beavers and remove their dams from the area.
“The landowner expects that if a beaver shows up in these places that we’ve prepared… and now starts flooding his cornfield, flooding his pastures, flooding his driveway, we’ve got to get that beaver under control,” said Rowe. “We don’t want to create a situation where we invite a beaver in and now there’s a huge pond on his property instead of a trout stream.”
He said the DNR mostly culls beavers on a case-by-case basis, but officials are monitoring some issues in areas that have seen repeated beaver damage.
Beaver culling occurs statewide every year and is not limited to trout streams. A spokesman for USDA Wildlife Services said the agency looted or removed 3,055 beavers statewide in 2021. Almost half of all beavers killed in 2021 – 1,279 in total – were taken from trout streams. The agency also removes beavers on behalf of county road and forestry departments, municipalities, and from lakes with wild rice beds. The counties with the most beaver kills were in northern Wisconsin, including Douglas, Sawyer, and Bayfield counties, which have the highest density of beavers in the state.
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However, as the state experiences more frequent heavy rains and resulting flooding due to climate change, some conservationists say the practice of killing beavers is harming trout streams and the surrounding area.
Bob Boucher studies beavers and how they affect hydrology and is the founder of Milwaukee Riverkeeper, an environmental advocacy focused on the Milwaukee River drainage basin. He said wildlife officials had started killing beavers based on the flawed science that beaver dams block fish migration and cause harmful warming of water in trout streams.
“Actually, they stabilize stream temperatures so that they’re cooler in the summer and warmer in the winter,” Boucher said. “If you stabilize the thermal climate flow, you also have more productivity because more beetles are farmed.”
He said these insects are key to trout populations thriving. Although fish prefer to live in cooler sections of water, they need the warmer parts for food.
Beyond trout populations, Boucher says, beaver dams are reconnecting rivers and streams to their natural flood plain. Over the past two decades, Wisconsin has experienced an increasing number of severe storms with heavy rainfall, particularly in northern and southwestern Wisconsin, resulting in flash flooding. Boucher said allowing beavers to build their dams on these waterways would help the waterways better manage the water inflow and stop it from flowing through the system.
He said wildlife officials are also killing otters on these waterways because they continue to use deadly traps for beavers. USDA Wild Services accidentally killed 146 otters last year as part of beaver removal efforts.
“They could move to non-lethal techniques, using flow devices and things like that,” Boucher said. “The[state]Department of Natural Resources is really damaging the wildlife of Wisconsin and I would say the waters of the United States.”
Rowe said the DNR recognizes the need for more research to better understand the actual impacts of beaver dams on local trout populations.
He said the department currently has one researcher working on the topic. He also said the DNR has been working to improve the habitat restoration process so they don’t accidentally attract beavers to an area that later needs to be removed. And he said the agency tries to reconnect trout streams with the natural floodplain in every habitat process because doing so has been shown to help projects be more successful and long-lasting.
