Courtesy of Rick Lanman
A Los Altos resident has solved the mystery of the missing beaver population.
A beaver was spotted in Palo Alto for the first time in 160 years last April, caught on Bill Litaken’s black-and-white trail cameras along Matadero Creek. Then in September, another one of Litaken’s cameras captured a beaver there – this time in color.
The photos confirmed what Los Altos resident Dr. Rick Lanman has believed for years – that beavers are native to Santa Clara County. While he said many naturalists assumed the aquatic rodents never lived here, Lanman built a case that they did. After years of research, he presented a scientific study in the fall showing that beavers existed in the county as far back as the 1800s.
A retired physician and biotech executive with a hobby of historical ecology, Lanman lives in a house near Adobe Creek. It was his curiosity about whether steelhead trout ever lived in the creek that led him to surmise that beavers once used the waterway as well. He said the previous owner of the house told him that he enjoyed fly fishing in the creek until the 1950s.
“That got me curious,” Lanman said. “I asked the water district if there was evidence of trout and they said, ‘No, there never were any trout in the creek.’ Well, I hiked the creek … and under El Camino (Real), there’s a 10- or 15-foot-tall fish ladder. Why would they build a fish ladder if there were never trout in the creek?”
Lanman ventured to Hidden Villa preserve in Los Altos Hills, where he was told by people who have lived in the area for many years that there were trout in the creek at one time. Lanman concluded that the fish were no longer there because a rectangular concrete channel had been constructed.
“A concrete channel probably eliminated the ability of steelhead trout to come up,” he said. “When you make a creek into a rectangular or trapezoidal channel, the bottom is perfectly flat. It rains, but you get an inch of water that’s going 30 miles an hour. No fish can swim against it.”
That solved the mystery of the disappeared trout. However, there was still the matter of the creek running dry. Lanman hypothesized that the reason was beaver ponds.
“Beaver ponds raise the water table,” he said. “They’re like percolation ponds. Water soaks into the ground and the water table rises. Then in the dry season, the high water table nourishes the creek and keeps it flowing.”
However, when Lanman went to the California Department of Fish and Wildlife (CDFW) to confirm his hypothesis, he said they told him that beavers never existed in California. Furthermore, in the 1937 novel “Fur-bearing Mammals of California” by Joseph Grinnell, the first director for UC Berkeley’s Museum of Vertebrate Zoology, the author writes there were beavers only in the Central Valley of California and none in coastal watersheds like the Bay Area.
Unconvinced, Lanman began looking elsewhere.
He first searched the California Academy of Sciences, where he found physical evidence of steelhead trout using the older names for the location and specimen.
“I searched for evidence of beaver and steelhead and thought there was none, until I realized that Adobe Creek used to be called San Antonio Creek,” Lanman said. “I also realized that steelhead trout have a different scientific name now than they did prior to 1900. When I searched on the terms ‘San Antonio Creek’ and the old Latin name for steelhead trout, there were three specimens in the California Academy of Sciences collected from the 1890s from our creek right behind my house.”
Although Lanman had evidence of trout, he still required evidence of beavers. Because many museum specimens in California were destroyed by the 1906 San Francisco Earthquake and fires, Lanman searched out of state in the Smithsonian Institution.
“I found a beaver skull in the Smithsonian collected in Santa Clara County in Quito Creek, which is the old name for Saratoga Creek,” he said. “That was the first physical evidence that beavers actually used a coastal watershed, namely a Santa Clara County or San Francisco Bay tributary.”
Through more research, Lanman discovered a beaver tooth in an archaeological dig in Del Norte County, more beaver remains in an archaeological site in Alameda County and, finally, a beaver skull in UC Berkeley’s Museum of Vertebrate Zoology.
“Another physician naturalist who was with the Los Angeles County Museum of Natural History had collected the skull after 1900 and given it to Berkeley, but Grinnell ignored it in his 1937 book,” Lanman said. “He just couldn’t believe it. His mind was fixed on what we call ‘shifting baseline syndrome,’ that is, when biologists believe that the animals that live here and their abundance and distribution historically is still the way that it was when the biologist was born.”
Through communication with CDFW biologists, Lanman learned the nearest sighting of beavers had been in upper Los Gatos Creek, above the Lexington Reservoir in 1980, after some beavers clogged a canal in the Central Valley. The beavers didn’t stop there; they kept moving down.
“By the 1990s, there were reports of beaver below the dam, in lower Los Gatos Creek and Los Gatos and Saratoga,” Lanman said. “Los Gatos Creek goes into the Guadalupe River, which goes into the Bay. In the 2010s, there were reports of beaver building dams in downtown San Jose, and now there’s beaver dams in a creek on the east side of San Jose.”
Then, there were beaver tracks at the end of San Antonio Road, north of Shoreline, and beavers in ponds in the Sunnyvale Water Pollution Control Plant. The beaver spotted in Palo Alto is the most recent sighting, according to Lanman.
“They’ve been gradually coming up the Bay, starting in Los Gatos Creek above Lexington Reservoir,” he said. “The same thing is happening in the North Bay. Beavers are moving. They’ve gone from Contra Costa County to Napa County to Sonoma County, and now I believe they’re almost around. … They’re using the Bay as a highway to gradually expand their territory.”
However, it seems that the beavers are unable to cross Adobe Creek into the Los Altos area because of the cement concrete flood control channels from El Camino to the Bay.
“No beaver, no fox, no bobcat, no animal can walk up the concrete,” Lanman said. “They’re completely exposed to predators: hawks, falcons, owls, coyote. So, beavers are unlikely to use those means of getting through our cities up to the highlands.”
The beavers’ return to the Bay Area brings both positive and negative changes, Lanman noted. He cited three positives: Beavers are keystone species that support many other species, they perennialize streams by raising the water table and beaver ponds can serve as protection from forest fires. The negatives: Beavers chop down trees and could potentially cause flooding. However, these two issues can be mitigated, Lanman explained.
“There is a very simple solution. You just mix sand in gray latex paint, and you paint the bottom of the tree trunk and they won’t gnaw on it; they can’t stand the feeling of sand on the trunk,” he said. “There are ways to manage (flooding) as well. You just put a pipe through the dam at the level you want and a wire cage around the upstream part where the beaver pond is so they can’t plug it up with sticks. It’s called a ‘beaver deceiver.’ These things have been well established on the East Coast.”
Lanman hopes the acknowledgment that beavers exist in the Bay Area helps with restoration and future scientific research in the area.
“I hope that this all serves as a guide to restoration and understanding what was actually here,” he said. “So much of it is misunderstood because we basically took the state from Mexico in the mid-19th century, and no museums were built. Then, when we finally build museums, it’s during the end of the 19th century and they get destroyed in 1906. And then we have the shifting baseline syndrome where everybody has these wrong assumptions. Do you know that there used to be elk here? Can you imagine?”
Credit: Source link
