Back in 2013 when I was working on the Guadalupe River educating thousands of students about our native Chinook salmon and Steelhead rainbow trout, Steve Holmes Executive Director of South Bay Clean Creeks Coalition and Roger Castillo Executive Director of the Salmon and Steelhead Restoration Group stumbled upon a wildlife discovery of the decade. While surveying for fall Chinook salmon they found a tree on the banks of the ancient Guadalupe River that had been gnawed.
Santa Clara Valley Water District was concerned about beaver being in downtown San Jose as their dams can cause flooding and damage to people's homes. We pointed out the fact that the beaver were in a multi-million dollar flood control project, and if they succeeded in building a dam the water would overflow into the tunnels of the flood control project, so they let us keep them. There would be no trapping and relocating. Greg Kerekez from the Urban Wildlife Research Project set up game cameras for monitoring. He noticed a newspaper strap around momma beaver's waist. We set up night and early morning shifts to try to capture her. We were finally successful after about a week, we cut off the strap and sent her in for a medical check up. She was then safely released back into the Guadalupe River. No doubt, she would have become another victim to plastic pollution (please cut your newspaper straps).
We were so excited at Guadalupe River Park Conservancy because historically it had been 150 years since beaver were seen on the Guadalupe River. I took initiative to begin to educate thousands of people about the beaver and hired Greg Kerekez who co-taught elementary school field trips with me. I would eventually work with graphic designers Wildways Illustrated to create an interpretive display in the visitor center of an actual beaver den on Los Gatos Creek that Greg had shown me. We would swim with the beavers!
So the question I always get is "where did the beaver come from?" In 1992 they were reintroduced above Lexington Reservoir in the Santa Cruz mountains by retired DFW game wardens so perhaps they have worked their way down Los Gatos Creek.
The other option is that they came from the Sacramento - San Joaquin River Delta. Although beaver do not live in salt or brackish water they can swim through them to reclaim freshwater habitats.
So either the beaver came down from above Lexington Reservoir or they are repopulating areas from the Sacramento - San Joaquin River Delta. Martinez, Ca has beavers and there is an organization called The Martinez Beavers: Worth A Dam ran by Heidi Perryman.
On November 9, 2018 a walker on Los Gatos Creek trail below Lexington Reservoir spotted this beaver.
How can you spot signs of beaver? Look for sticks that have the ends gnawed like the photo below.
I included a photo of their scat so you know what to look for, the scat would be in the water at the bottom.
Beavers which were nearly hunted to extinction for their fur in the 1800's are ecosystem engineers and contribute to watershed restoration, especially with climate change and drought. In the past fishery biologist believed that beaver dams blocked salmon migrations but a study by Michael M. Pollock, an ecosystems analyst with the National Oceanic and Atmospheric Administration, shows the opposite: wild salmon are adept at crossing the beavers’ blockages. Their ponds create rearing and summer hold over spots for not only salmon and trout but for sensitive amphibians and reptiles.