River otters and beavers are coexisting in a Sonoma creek

Sometimes it’s a case of mistaken identity, a river otter misidentified as a beaver – or the other way around – but both are here in Sonoma and living in close proximity to one another.

“If I had a dime for every time an otter was misidentified as a beaver I would not have to raise funds for my project,” said Megan Isadore, co-founder and executive director of the River Otter Ecology Project.

Photos of North American River otter provided to the Index-Tribune for a story about a beaver dam in Sonoma misidentified the animal as beaver. Isadore and others correctly identified the critter in the photo.

“It’s a very common mistake,” said Heidi Perryman, beaver advocate of Worth a Dam, a non-profit organization dedicated to maintaining beavers in Martinez.

She said the two animals are found in similar habitat, but it’s not because they seek one another’s company.

“They are not best friends,” Perryman said. “They are like neighbors; neighbors who don’t really get along.”

Otters are carnivores, she explained, and will take a beaver’s baby (called “kit”) so beavers will protect their young and chase away otters.

There are a number of differences between the animals, such as beavers are vegetarian and river otters will eat crayfish, crab, insects, frogs, insects and snakes, Isadore said.

“They eat a lot of water birds, even birds as big as pelicans,” she said. “They’ll eat small rodents if they can get them. They’re not very picky.”

Worth a Dam provides identification help on its website. Otters have long, sleek bodies compared to a beaver’s rounder frame. Beavers can weigh about twice as much as an otter. Otters are white in color around their muzzle with a lot of whiskers. Their tales are quite different, too. Where an otter tail starts wide at the back end it tapers into a point, whereas a beaver tail is flat, like a paddle.

Otter are “very common” in the Bay Area, Isadore said, and they are found all over in Sonoma, Napa, Solano and Marin counties, and even in the East Bay as far south as Fremont. Her otter project has “been collecting sightings for eight years.”

Sightings maps can be found on the project’s website RiverOtterEcology.org. Isadore cautioned that the sightings identified on the website are only sightings that have been submitted there, and in no way should be considered a comprehensive count or location limitation of otter habitat.

The Sonoma otters are probably taking advantage of and enjoying the habitat the beavers created here, but the presence of otters doesn’t mean the beavers have left town, the experts said.

Some local residents and the nature experts are in agreement that the hole cut into the beaver dam recently by workers with Sonoma Water was not effective.

Perryman is upset that the agency referred to the hole as a “notch.”

“You don’t ‘notch’ with a chainsaw,” she said. “You notch a dam with a rake or a pair of clippers.”

She said it’s difficult to get agreement on what “notch” really means. “Ripping out the dam, even if that’s what they did, it’s not a problem for the beavers. They’re not looking for retirement.”

Barry Dugan, principal program specialist with Sonoma Water, said the hole cut was a temporary measure to prevent erosion and for flood control and to lower the level of the water there.

“The bypass channel by the dam” was eroding part of the road, and they consulted with water stream maintenance and Department of Fish and Wildlife and followed their recommendations “of how to lower the dam,” Dugan said.

Where water backed up in that area it caused damage to some trees, and flooding became a concern, he said.

“In terms of the long-term plan, we will discuss it with our biologist, and develop a long-term plan,” which could include a pond leveler.

Cutting holes in the dam will not solve the problem of bypassing water, experts said. Beavers will just continue to fix whatever hole is cut in the dam.

Dugan said the agency installed a wildlife camera near the dam last week. They will monitor the dam, creek and beaver activity to help them plan for a long-term solution.

On the Sonoma Ecology Center Facebook page is a video, taken in July, of a beaver at work on a tree: facebook.com/SonomaEcologyCenter/videos/2386053161672186/.

Contact Anne at anne.ernst@sonomanews.com.