Estuary Beavers: Nuisance, Regular Beaver or Something Special?
By James Horan
An estuary beaver? You probably have never heard about them. Until 15 years ago, when they were discovered by Dr. Greg Hood, a scientist with the Skagit River System Cooperative, no one else had either. He discovered beavers living in the Skagit River estuary system where salt and freshwater mix. Surprisingly, beavers (thought to be dependent on fresh water systems), were living and thriving in this brackish environment, building dams and lodges, creating a habitat essential for themselves, vegetation, and fish, including juvenile Chinook salmon. Prior to Dr. Hood’s discovery, no one in the scientific community had documented beavers living in estuaries. Since then, he has found evidence of beavers (248 dams and 5 lodges) from the estuaries of the Fraser River Delta in BC to the tributaries of the Columbia River, with more likely to be found.
Historically, North American beavers (Castor canadensis) enticed fur trappers to explore farther and farther west in search of their valuable pelts. As supply diminished and other materials became available commercially, settlers tended to view their industrious dam building as a nuisance. Beaver dams were considered a detriment to property development, because land, once drained, could be used for homes, barns and crops. Beavers were considered so undesirable they were almost wiped out across North America. Fortunately, in recent decades both public and private landowners began to recognize beavers add value to the environment. In the places where they build dams, diverse habitat is created, water is slowed, soil erosion is reduced and helpful vegetation can grow.
It turns out “estuary” beavers are North American Beavers who are able to make a living in brackish, tidally influenced estuaries. They build dams and lodges adapted to tidal movement ensuring at least a foot of water at low tide so they can always enter their lodge from underwater. The dammed pools support baby fish (fingerlings) including Chinook salmon, stickleback, and prickly sculpin. The dams create habitat in the tidal emergent zone for sedges and grasses where Great Blue Herons feed. Logs that settle in the tidal marshes become nurse logs where woody plants can grow, creating diverse habitat.
For more information, check out this video link to “The Beavers of Our Tidal Waters” https://youtu.be/IYYULzuExiA?si=DM7guXXcLyRJDV_F
Thanks to Laura Arber, WA Dept of Fish and Wildlife and Ryan Munes, Wildlife Refuge biologist for their help with this article. Photo by Rob Crisler
