SAN JOSE -- A family of beavers has moved into Silicon Valley, taking up residence along the Guadalupe River in the heart of downtown San Jose.

The discovery of the three semiaquatic rodents -- famous for their flat tails, brown coats and huge teeth -- a few hundred yards from freeways, tall office buildings and the HP Pavilion represents the most high-profile Bay Area sighting since a beaver family settled in Martinez in 2006. The discovery of those beavers sparked national headlines when city leaders at first tried to remove them and then backed down after public outcry.

The appearance of the furry mammals in downtown San Jose is believed to be the first in 150 years.

As word about their new home spreads, the animals are being held up as a symbol of the slow but steady environmental recovery of San Francisco Bay and its streams after decades of pollution and sprawl -- a hopeful sign of the resilience of nature in the nation's 10th largest city.

"My reaction is cartwheels. I'm so excited," said Leslee Hamilton, executive director of the Guadalupe River Park Conservancy in San Jose.

"It's amazing we have this living river in downtown San Jose, with great blue herons, egrets, chinook salmon, steelhead trout and now beavers. We live in such a highly urbanized area, it's a delight to walk out and actually see that wildlife are able to survive here."


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The beavers, a female adult and two yearlings, have been swimming between the Children's Discovery Museum and the St. John Street Bridge. Beavers are nocturnal and rarely come out in the daytime. But some people have reported seeing San Jose's beavers a few times just after sunrise, Hamilton said.

They haven't built a dam, which might raise flood control issues.

"Our perspective is that there's really nothing to do right now except monitor the situation. We have no plans to do anything," said Marty Grimes, spokesman for the Santa Clara Valley Water District, which is responsible for flood control on the river.

If they do build a dam, it is in an area where there is a large overflow channel, built as part of a $300 million project in the 1990s to protect downtown from flooding. So any water that backed up could flow harmlessly into that channel, Grimes said.

"We've got the overflow capacity. There are worse spots for them," he said.

Nobody knows where the beavers came from. The key theories at the moment are that they were part of a colony that has been known to be living in the upper reaches of Los Gatos Creek, upstream from Lexington Reservoir, for at least 20 years. They could have swum down Los Gatos Creek, because their current home is close to where the creek flows into Guadalupe River.

Another thought is that maybe they are connected with the Martinez beavers, who are believed to have originally come to the Bay Area from the Delta.

"Our female beaver produced 15 live births. They've all dispersed," said Heidi Perryman, president of Worth a Dam, a Martinez nonprofit that advocates for that city's beavers. "They could be in San Jose. There's certainly a chance."

There are still four beavers living in Martinez in Alhambra Creek. Flood control concerns were reduced by putting a pipe in the beaver dam that regulates the flow of water. So if the water gets too high, it drains out downstream.

The beavers in downtown San Jose -- who may become as well-known as the peregrine falcons who live atop San Jose City Hall -- were first discovered about two weeks ago when San Jose resident Roger Castillo noticed telltale chewing marks on trees near the Shark Tank.

Castillo, who gained fame in 2005 for finding the skull of a 14,000-year-old Columbian mammoth while walking his dog along the river, sent news of the find to amateur naturalists around the South Bay. A few days later, on March 30, one of them set up two remote cameras in the trees near the St. John Street Bridge and the confluence of the Guadalupe and Los Gatos Creek.

When Greg Kerekes checked the memory cards in the days that followed, he saw three beavers frolicking, climbing on logs and chewing on trees.

"This is a sign that things have recovered enough that there's enough native vegetation to sustain a family of beavers," said Kerekes, who works for the conservancy and for the Santa Clara Valley Audubon Society.

"Every time I go down there I see something new, a new butterfly or a new bird. There are still challenges dealing with the homeless and litter, but overall it's a good sign of the ecosystem's health that the beavers are there."

Beavers are believed to be native to the Bay Area. A skull in the Smithsonian is from a beaver found in Santa Clara in 1855.

Over the years, they were hunted across California and most of the U.S. for their pelts. To this day, they can be hunted without limit by anyone with a hunting license in 42 of California's 58 counties, including Alameda and Contra Costa, between Nov. 1 and March 31. It is against the law to hunt beavers in 16 counties, including Santa Clara, San Mateo, Marin, San Francisco and Santa Cruz.

Beavers that are damaging property can also be trapped and killed under permits issued by the state Department of Fish and Wildlife.

In recent years, beavers have been spotted along the bay front in Sunnyvale, Vallejo, American Canyon and Benicia.

The vegetarian animals live up to 15 years. Research shows they benefit salmon and other animals by keeping water in dry streams year-round and pooling water behind their dams, which allows sediment to settle and provides cool water for young fish.

"Whether these beavers came from the bay or Los Gatos Creek, I don't think we know," said Rick Lanman, a Los Altos physician who has published scientific papers on California beavers. "As long as we keep improving our environment, we are going to see more recolonization. It is a really cool story."

Paul Rogers covers environmental issues and resources. Contact him at 408-920-5045. Follow him at Twitter.com/PaulRogersSJMN.