Threatened beavers return to Sonoma

When a Sonoma Valley woman saw a tree behind her yard felled and chiseled by V-shaped gnaw marks, she was surprised and not quite sure what had caused the damage.

Soon she learned it was the work of something she never expected to find near her home: a beaver.

'I really now understand the phrases 'busy beaver' and 'eager beaver.' We wake up in the morning and look out and think 'wow' look how much they did overnight,' she said. Every day that passed more of the tree disappeared developing into an hourglass shape where the beaver noshed, and late last week the tree was down.

The woman asked not to be identified by the Index-Tribune in order to protect the beaver and their habitat from the beaver-curious.

'It is amazing. I'm so delighted that they're here, and I hope people will leave them alone,' she said, adding that it's important to keep dogs on leashes so that they don't disturb the beaver.

Beaver are prey animals and easily spooked, said Richard Dale, executive director of the Sonoma Ecology Center. He said he's seen beaver in the daytime, but as soon as they detect his presence they slap their tails and disappear.

Indication of their activities are usually more evident, such as the gnaw marks the local woman found. Dale said they make diagnostic V-shaped marks on trees, which they eat and use to build lodges where they hide for safety. They'll use pretty much anything to build the lodge but typically they are made of sticks, rock and mud.

They chew deciduous tree bark and cambium – the soft tissue under the bark – and are partial to willow, cottonwood, maple and a couple other tree species. But they will travel farther away from the protection of their lodges for aspen, said Kate Lundquist in a radio interview in January with KMUD, a radio station located in Humboldt County. Lundquist is the director of the Occidental Arts and Ecology Center's Water Institute and the Bring Back the Beaver Campaign.

Beaver are the largest of the rodent species in North America and can grow to up to about 60 pounds. Their incisor teeth 'keep growing and growing' so they are 'constantly working their teeth' to keep them under control, Dale said.

'They've been part of the ecosystems for thousands of years. Many systems are dependent on them,' said Dale, who has been studying them for about 25 years. Dale said beaver sightings in town are rare, but he recalls hearing of occasional sightings north of the city since the early 1990s.

'I was blown away when I saw them,' he said of the recent sightings.

While some people consider them a nuisance, beaver are called 'keystone species' or 'grassroots conservationists' and are considered vital to riparian habitats. They will build lodges in three different ways – open-water lodge, bank lodge or bank den, or burrow – and one colony may have several lodges scattered around their home range.

The lodges extend wetlands, elevate water tables and allow for recharging of aquifers and wells, and provide 'habitat for other critters,' Dale said. In areas where there are beaver lodges vegetation and watersheds stabilize, and downstream flooding and silt runoff is reduced.

Beavers are excellent engineers, Dale said. They know how to chew away a side of a tree so that when the tree falls, it lands where the beaver wants it.

'They can figure out how to drop a tree into the water,' he said.

Beaver were plentiful a couple centuries ago, but their pelt was used for currency, hats and other products, Dale said. Now they are threatened by loss of habitat and depredation by humans.

Lundquist has been working with lawmakers to change the policies and language in some laws to protect beavers, she said in the radio interview.

Research is showing what the loss of the animal is doing to our ecosystems.

'We're just now realizing the impact of having removed most of the beaver across California and we're starting to see how that's had a very profound long lasting effect of de-watering a lot of our systems. Now we want to try and be a little more aware of that,' Lundquist said.

Dale and others who have seen beaver or evidence of beaver activity are thrilled to know they are in Sonoma Valley.

'It's so incredible, to see something like a beaver here. It reminds us that we're a part of everything,' said the Sonoma Valley woman.

For those times when a beaver is destroying valuable plants – such as vineyards – there is 'beaver deceiver' technology out there, Lundquist and Dale said. Wrapping trees with wire will protect the bark, and if the lodge is in a place where too much water is backing up, there are simple cost-effective ways to release some of the water from the pond beavers have created.

'They hate the sound of running water,' Dale said, so it's important to set up the culvert in such a way that the beaver doesn't feel obligated to plug a hole.

Editor's note: This has been updated to reflect that beavers are vegetarian.

Contact Anne at anne.ernst@sonoma.news.com.