Sep 24 2018

Critter Corner: Busy Beavers
A Boon to Wildlife Habitat

By Stefani Spence, Land Steward

The North American Beaver (Castor canadensis) was once hunted to near extinction in New Jersey for its fur. Nowadays their population has recovered and beavers can be spotted at Crystal Springs Preserve and throughout Hunterdon County. Beavers are often considered a pest, but they play an important role in environments along stream banks. 

Beavers are often called “ecosystem engineers” for the way they modify their environment to suit their needs, like humans do. If there isn’t already a pond where beavers want to build their lodge, they will make one. Using their front teeth, they fell trees to make dams, eating the bark and leaves for food. The beavers dam the stream by placing vertical poles across its berth, filling the gaps with branches, weeds, and mud. The stream becomes a pond, where they then build their lodges out of mud and branches, digging out underwater entrances so predators like coyotes and bears can’t get in. 

Beaver dams cause drastic changes to the environment, but end up creating more habitat for other species. For this reason, beavers are a keystone species, or a species that has a critical impact on the structure of its ecosystem. Beaver dams slow the flow of water in the stream, which creates pools and riffles that are essential for fish like salmon and trout to reproduce.


The ponds created by beaver dams can drown trees, but this creates standing dead wood that serves as habitat for insects, birds, and mammals. The wetlands created by beaver ponds are excellent habitat for waterfowl like the Great Blue Heron and Wood Duck, as well as turtles, amphibians, and aquatic plants. In torrential rainfall events the wetlands also help contain stormwater and capture sediment, reducing flooding and pollution of rivers and streams.  

Unfortunately, beavers and people don’t always get along. Beaver dams can flood people’s properties upstream, and beavers frequently plug culvert pipes, which leads to flooding that can damage roads.

For those dealing with unwanted beaver activity, non-lethal measures exist. Humane trapping and relocation has a high failure rate due to resettlement by new beavers, but there are numerous ways to mitigate unwanted flooding while preserving the ecosystem benefits beavers provide. Simple options include fencing around culvert openings to prevent beavers from plugging them.

More complex methods may involve drainage pipes or submerged intake devices to control the water level in the beaver pond. These are only effective when installed with measures to muffle the sound of moving water, which otherwise alerts beavers to the source of the drainage and prompts them to plug the pipes or build a new dam further downstream. 

In New Jersey, where many of our rivers are in dire need of restoration, beaver dams can help restore degraded riparian systems. Slowing stream flow, creating backwatered areas, and reconnecting a stream with its floodplain are objectives accomplished by beavers and river restoration projects alike, though the beavers get it done at a fraction of the cost. Restored river systems mean less flooding during storms, better water quality, and better fishing and birding for us, and better habitats for New Jersey’s native species. When you look at it that way, busy beavers might not be such a bad thing! 

2 Responses to Critter Corner: Busy Beavers
A Boon to Wildlife Habitat

  1. Gordon Sell June 14, 2019 at 9:52 pm

    Saw a beaver swimming by the kayak beach in Spruce Run Reservoir today (6/14/19) about 7pm. I spend a lot of time sailing there, but never saw a beaver before.

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