The Current

Are saltwater beavers a thing? Scientists observe Canadian critters in potentially deadly habitat

Our documentary A Salty Tail explores beaver behaviour that is puzzling scientists. Canada's national animal is being discovered in saltwater zones, despite the long-held understanding that the rodents only live in freshwater. Are saltwater beavers actually a thing?

Rescued beavers with saltwater poisoning are dehydrated, disoriented

City of London has established a 'beaver protocol' to ensure conflict with the 'smart and industrious' critter doesn't cause flooding or other problems. (Shutterstock)
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Originally aired June 18, 2019.

At the end of long day studying saltwater marshes in northern Washington State, scientist Greg Hood had a surprising encounter.

"I was walking down the channel, and the water was about … thigh-deep — and a beaver was swimming towards me," said Hood, a senior research scientist with the Skagit River System Co-operative in La Conner, Wash.  

When Hood tried to take a photo, the beaver "swam the other direction… but that was pretty exciting!" he told CBC Radio's The Current.

Hood's surprise and excitement comes from the belief that — as every card-carrying Canadian knows — beavers, one of Canada's national symbols since 1975, live in freshwater systems.

But while Hood had observed that beavers were setting up home in saltwater, other experts say that it could make them sick, or even kill them.

Scientist Greg Hood was finishing work one day when he ran into a beaver swimming in the Skagit River in La Conner, Wash. (Jessica Linzey/CBC)

Saltwater poisoning can kill, says animal welfare worker

Breanne Glinnum has seen beavers with saltwater poisoning at the Critter Care Wildlife Society, her clinic and rehab centre in Langley, B.C.

"Some of them are coming in just a little bit dehydrated. We give them fluids, we make sure they're eating and off they go," she told The Current.

"Others are coming in completely disoriented, walking like they're intoxicated; some of them aren't even walking at all, they're completely flat out," she said.

"They're cold, and then we put them on heat. Some of them don't even make it past the heat, as soon as they warm up, they pass away on their own."

Douglas the beaver arrived at Critter Care Wildlife Society in April 2019 with saltwater poisoning, but has since made a full recovery, the clinic says. (Submitted by Critter Care Wildlife Society)

Over a two-month stretch last year, Glinnum says Critter Care picked up 13 sick beavers, more than half of which were suffering from saltwater poisoning. Those numbers have been climbing over the years, she added.

She thinks the beavers are ending up in saltwater because of decreasing freshwater habitats.

She explained that the rodents kick their young out when the kits reach two years old. The evicted youngsters then have to swim off and find their own body of water to call home.

If that search leads them to saltwater, they can end up in her clinic.

She thinks it's "really insane" that beavers are setting up home in the tidal marshes in Washington, but suggested they could be surviving by finding their food elsewhere, so they don't ingest as much saltwater.

Beavers are building with intention: biologist

Before Hood's first encounter with a beaver in the tidal marshes, he says he had been stumbling across "kind of weird-looking beaver dams."

"They didn't fill up a channel entirely, they were kind of low in the channel, and I'd never heard of beaver in tidal marshes," he told The Current, which made him reluctant to jump to that conclusion.

"So it was a puzzle for me. I was curious about it," he said, adding there's not enough interest in the subject to secure any funding for official research.

But wildlife biologist David Bailey has looked at how beavers living in saltwater have been adapting in Tulalip, Wash.

Wildlife biologist David Bailey has looked at the habitat of saltwater beavers in Tulalip, Wash. (Jessica Linzey/CBC)

Their dams are built lower than a normal dam, and disappear under the water at high tide, he told The Current.

He explained that they're built like that to stop the power of the tide from breaking them apart. The doors to their lodges are also at different heights to accommodate the rise and ebb of the water.

As Bailey realized what he was looking at, he thought: these are beavers with intention, they've settled here.

"It's definitely crazy, it's definitely eye-opening," he said.

"If I was trying to be a beaver and live out here, I don't think I would do this, it doesn't make any sense."

Bailey bounces gently on a lodge, to see if there are beavers inside. (Jessica Linzey/CBC)
Talking to The Current's Jessica Linzey, biologist David Bailey describes the sounds that tell you a beaver is nearby. 0:46

However, Hood disagrees with other scientists that it's "crazy" to find beavers in this habitat, and suggests maybe they've always done this, but we've never thought to look.

He thinks "it's a symbol of a forgotten landscape."

"People seem to think that science has discovered everything, even something like mental history, and in fact there's still a lot that we don't know about these systems," he said.

"Discovering tidal beaver is a reminder of our ignorance, and that we still have a lot to learn."

Click 'listen' near the top of this page to hear the full conversation.


Written by Padraig Moran. Produced by Jessica Linzey and Joan Webber.

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