The beaver is again: Pair of the semiaquatic rodents noticed in Palo Alto | Information

0
108
The beaver is back: Pair of the semiaquatic rodents spotted in Palo Alto | News

More than 160 years ago, the sight and sound of beavers in the local streams was probably commonplace, splashing their paddle-like tails with their brown bodies slicing through the water with noses just above the waterline.

Exterminated by hunting, the North American beaver, scientific name Castor canadensis, has not only fallen into oblivion locally; According to scientists, it was long assumed that it never existed here at all.

But now the beaver is back. In April, the first beaver was sighted in a remote stretch of Matadero Creek. Today there are two of the chubby herbivores. If they successfully recolonize local streams, the presence of these large, semiaquatic rodents could herald a return of other long-vanished species, including salmon, endangered amphibians and birds, according to scientists.

The beavers could also play a crucial role in replenishing groundwater, repairing erosion of river channels and restoring wetlands, said Dr. Rick Lanman, a Los Altos-based physician, scientist, historical ecologist and President of the Institute for Historical Ecology.

For Lanman, whose seminal work found beavers native to Santa Clara County, the journey to rediscovering beavers began in 1987. His home in Los Altos is near Adobe Creek.

He began considering the possibility that beavers might be native to the western Bay Area after hearing stories from old-timers like then-80-year-old Herb Bickell.

“He said, ‘You know, I used to fly fish in the backyard up until the 1950s,'” Lanman recalled.

Lanman began to wonder why the creek has been dry for half a year now and there are no fish.

“One of my theories was that maybe there were beavers. Beaver ponds are like seepage ponds. They raise the water table so that in our dry season, when the water table is high enough, it fills up the stream again. He told me that the stream used to flow all year round. So did Senator Alan Cranston, who lived just up the river from us,” Lanman said.

But scientists had long dismissed the beaver as not native to the Bay Area. Joseph Grinnell, the first director of the Museum of Vertebrate Zoology at the University of California, Berkeley, wrote a book in 1937 entitled Fur-bearing Mammals of California, which claimed that beavers never lived in the Coast Range watersheds or in the United States Sierra given Nevada, Lanman said.

“And then I met an archaeologist who found a buried beaver dam in the Sierra Nevada. And that was my first publication on historical ecology in 2012. It was a buried beaver dam at about 12 feet down,” he said.

Radiocarbon dates from the hives showed the dam had stood there for hundreds of years and was likely rebuilt by successive generations of beavers. The beavers apparently stopped building the dam around 1850, coinciding with the gold rush, he said.

“And that was when all these Anglo-Americans were chasing everything. So when we get to 1937, Prof. Joseph Grinnell… suffers from what we call ‘shifting baseline syndrome,’ where you think how things were when you were born. That’s how things have always been. It’s a baseline shift,” he said.

Physical evidence of beaver habitation in the Bay Area was also sparse.

“If you look in California museum records, you won’t find a beaver,” he said, noting that Stanford University’s local collections were largely destroyed in the 1906 San Francisco earthquake and the beavers were likely gone from most places, when people started collecting . The semiaquatic beavers were chased out of the area in the mid-1800s, Lanman said.

“But if you look in the Smithsonian, it turns out there’s a beaver skull that was collected from Saratoga Creek around 1855. So that was the first physical evidence of a Bay Area beaver in a tributary of the South Bay. And we published that work in the California Fish and Game Journal in 2013,” he said.

In April, nine years after Lanman and the Institute of Historical Ecology published their findings, Palo Alto resident Bill Leikam, co-founder and executive chairman of the Urban Wildlife Research Project, documented the first modern record of beavers in a remote stretch of Matadero Creek. Leikam, known for his research on the Baylands’ famous gray foxes, captured images of a beaver with wildlife cameras after being warned by a friend. First one, then two beavers appeared in the spooky black-and-white images.

Then, early one morning in September, Leikam had a direct encounter with a lone beaver swimming in deep water. He took a color picture with his camera.

He was walking around the area on a sunny afternoon the other day. If the critters were present, it was still too light for them to appear, he said. Beavers are crepuscular — they’re mainly active at dusk and dawn, he said. But he described what happened to him that morning when he took the picture.

“They probably weigh around 30 to 40 pounds and eat mostly willow,” he said.

Again, physical evidence is hard to find. There is no beaver dam and no tracks. Leikam said they probably live in a cave they built deep in a creek bank. The area would be camouflaged by trees and scrub; Its entrance is probably underwater and inclined into the bank.

Beavers don’t always build dams; They mainly do this in shallow water to raise the level, he said. According to Lanman, beaver burrows are also not likely to endanger wide levees, nor are their dams likely to pose a flood hazard.

When beavers built a dam in San Jose, the Santa Clara Valley Water District wanted them removed, but Lanman argued against it.

“The beaver dams cannot withstand storms like our winter storms. They just blow them out and then build them up again the next spring and summer. So you are not really a problem. They’re not increasing the flooding,” he said.

How they made their comeback

Beavers got another chance to return to Santa Clara County’s waterways in the 1980s after being reintroduced into Los Gatos Creek. Problem beavers in a Central Valley canal had to be removed or eradicated by California Fish and Wildlife employees. They chose to relocate and release the beavers to upper Los Gatos Creek, where they reach Lexington Reservoir, although the animals were still considered a troublesome species and translocation wasn’t widely allowed — and still isn’t.

Still, taking the beavers to a relatively harmless spot and seeing what might happen seemed like a worthwhile experiment.

The animals eventually made it over Lexington Dam and down into Los Gatos Creek, where they built stock dams. They didn’t stop there.

“In the next decade, a dam will appear in San Jose. Los Gatos Creek empties into the Guadalupe River, which flows through downtown San Jose into the South Bay,” Lanman said.

In the early 2000s, beavers appeared in Coyote Creek to the east, and in 2008 in San Tomas Aquino Creek, where they reach the Sunnyvale Water Pollution Control Ponds. Beavers have been photographed at Moffett Gate; Their tracks, including a stern tow in the mud flats, were photographed in Charleston Slough, just east of Adobe Creek dam, he said.

“It’s right on the San Antonio Seawall on San Antonio Road. So you are right on the border near Palo Alto. And then there are some reports of a beaver here and there. These are probably 2- to 3-year-olds who “broke up after spending a few years with their family in their teens,” Lanman said.

Using the salt water in San Francisco Bay to migrate from one freshwater tributary to the next, beavers are now reaching the creeks of Palo Alto. However, they are unlikely to migrate up the concrete channels of the Matadero and Adobe creeks, where they and other wildlife lack vegetation cover and are exposed to hawks, owls and other predators, Lanman said.

The concrete waterways are an example of how wildlife habitat is being fragmented and the movement of species hampered. Fragmented and blocked passageways caused by inhospitable habitats, buildings, highways, and other obstacles cause wildlife to live in isolated niches, leading to inbreeding and disease. An entire population once affected can be wiped out, said Leikam, who witnessed the same tragic events with the Palo Alto Baylands foxes and some raccoons.

However, the trail to San Francisquito Creek could be a turning point for the beavers and other wildlife.

“It’s not concrete because it’s the Santa Clara County/San Mateo County border and the two counties couldn’t agree to pay for all the concrete to turn it into a flood channel.” So San Francisquito Creek stays natural until you get up Stanford’s Searsville Dam,” Lanman said.

The two beavers spotted in Palo Alto this year, if they are a compatible pair, could potentially mate and start a colony of small beavers with the potential to inhabit San Francisquito Creek and adjacent San Mateo counties to pull. At a certain point, in a favorable habitat and with an open corridor, the population could skyrocket, Lanman said.

Climbing the San Francisquito Creek would create the corridor into the upper watersheds that scientists have hoped for to encourage all types of animal populations.

“It’s going to be really interesting. When they get there, they can come upstream, and that’s a big system. And it’s important because beavers provide important ecosystem services. Beaver ponds are insect cafeterias for coho salmon spawn 200 times if there is a beaver pond for them. It’s a sheltered spot full of bugs,” he said, and provides shelter for steelhead trout and chinook salmon.

Those fish populations are collapsing, but the beavers could be helping them revive, he said.

“Beavers are the only thing we haven’t tried. They have these important ecosystem benefits, not just for our trout and salmon, but for all kinds of critters: red-legged frogs, which are federally endangered; Birds that are federally endangered and depend on hunting over water and bats that hunt over water.”

Beavers are a key species – a species on which the survival of other wildlife largely depends – and they have already proven their immense value in reviving ecosystems.

In the town of Martinez, beavers colonized Alhambra Creek, transforming the waterway from a trickle into several bountiful ponds and dams. According to the website martinezbeavers.org, the creek is now home to steelhead trout, river otters, mink, green herons, crested mergansers and tule bass, a species of fish that has probably never been seen in Alhambra Creek before.

Lanman and Leikam hope the Palo Alto beavers will also usher in an enriched ecosystem.

“It’s so exciting for me to see that ten years later, after we published these papers, they finally surface a few miles from my home,” Lanman said.