Beavers are notorious for gnawing on aspen trees. (Image: Sierra Wildlife Coalition)

Beavers often get a bad rap, when really they should be rewarded for being one of Mother Nature’s natural removers of fine sediment.

“Beaver physically modify the environment more than any other non-human organism in the Northern Hemisphere. They are appropriately named ecosystem engineers,” Erin Miller, aquatic biologist with Lake Tahoe Basin Management Unit, said. “The dam structures they build change how water flows over the landscape, which helps to create habitat for many threatened and endangered species both in the stream and adjacent wetland habitats. Furthermore, beaver dams slow the flow of water and spread it across the floodplain. This process can reduce the intensity of floods, reverse the effects of channel erosion, and promote groundwater recharge. In Lake Tahoe, beaver dams have been shown to enhance water quality by trapping sediment that flows downstream.”

The U.S. Forest Service is responsible for their habitat.

“There are beavers everywhere now so it is obviously good habitat,” Sherry Guzzi, co-founder of Tahoe City-based Sierra Wildlife Coalition, said of the basin.

This nonprofit formed in 2010 because of a beaver-killing incident in Kings Beach.

Beavers are so beneficial that in 2022 the California Department of Fish and Wildlife rewrote its beaver policy.

“This update is intended to ensure that staff are considering the benefits of beaver presence against the impacts of beaver depredation in each incident and evaluating whether there are feasible non-lethal deterrents that can effectively alleviate the conflicts and facilitate human-beaver co-existence,” said Valerie Cook, CDFW’s beaver restoration program manager.

Evidence of old beaver activity on the South Shore of Lake Tahoe at Taylor Creek. (Image: Lisa Herron)

Beaver facts

“It is now established that beaver were native to the Sierra Nevada until their extirpation by fur trappers in the 19th century,” Miller with LTBMU said. “Archaeological and ethnographic evidence indicates that beaver were present in Sierra watersheds prior to westward expansion.”

A paper by California officials in the 1930s said otherwise. Since then, better data and research has proven beavers are native.

Cook with CDFW explained, “Due to overexploitation by the fur trade (in the) late 1700s-1800s and later the compounding impacts of managing beavers as a nuisance in the early 1900s, beavers had been extirpated from many of California’s watersheds. In the 1930s to 1950, beavers were translocated and released in multiple locations in California, though I have not seen any data or evidence indicating that beavers were translocated into the Tahoe basin. Based on the available records, only one translocation occurred in El Dorado County—1938, the U.S. Forest Service translocated four beavers and one in Placer County; 1945, four beavers, by California Fish and Game. Neither of these records indicate the actual release site, so we don’t know where these were relative to the basin.”

No agency could provide an approximate number of beavers in the basin, which in part is because they are nocturnal.

North American are the Tahoe beavers. Eurasian beaver is the other type that exists in the world. The two do not breed.

“The Tahoe basin is home to a species known as mountain beaver. Not a beaver at all, but a much smaller than an American beaver, ground-dwelling rodent of the forest floors of the Tahoe basin,” Jamie Roice-Gomes with the Nevada Department of Wildlife said.

Guzzi says beavers are North America’s largest rodent; with adults weighing more than 40 pounds. These mammals are herbivores, chew with top and bottom incisors, don’t hibernate, mate for life, and live to about 15.

“They are aquatic mammals, and are most comfortable in water. They are very good swimmers. Their back feet are webbed,” Guzzi said. “They are very slow on land and awkward.”

Coyotes, bobcats and bears are a threat to young beavers, otherwise humans are their main foe.

Beavers last fall make a dam at Taylor Creek near South Lake Tahoe. (Image: Lisa Herron)

Tahoe projects

Sierra Wildlife Center has been instrumental in working the LTBMU and others to eliminate conflicts beavers may pose.

“The act of removing beaver dams in Taylor Creek to facilitate migration of kokanee salmon is no longer in practice. Beaver dams in Taylor Creek are only manipulated when they create unsafe conditions or threaten infrastructure,” LTBMU  aquatic biologist Sarah Muskopf said.

She wrote her 2007 thesis about beavers.

“The thesis was focused on the impacts of beaver dam removal and nutrient transport: Did beaver dam removal in Taylor Creek increase the amount of total phosphorous entering Lake Tahoe? The results implied that the presence of beaver ponds in Taylor Creek could improve water quality by reducing the phosphorus load entering Lake Tahoe when flows are increased from Fallen Leaf Dam,” Muskopf explained.

Sierra Wildlife Center helps entities with installing levelers and deceivers that divert water to prevent flooding while keeping the beaver dams intact. The center also uses paint mixed with sand on tree trunks to stop beavers from chewing aspens or willows. They don’t like the grit.

Sierra Wildlife Coalition’s main focus today is educating the public and agencies about beavers’ benefits and how to co-exist with them.

Note: A version of this story first appeared in Tahoe In Depth.