In a deep muddy creek near Silicon Valley’s busiest freeway, a large furry head pokes up. And then quickly submerges. The brief sighting, along with a growing collection of video footage, confirms something remarkable: After being hunted to extinction in the 1800s, the North American beaver is returning to the creeks of the San Francisco Bay Area. Ecosystem explorers, beavers were re-introduced to Lexington Reservoir in Los Gatos about four decades ago, and made homes in upper Los Gatos Creek. Since then, they’ve expanded their range north along the edge of the Bay to the Guadalupe River, Coyote Creek, San Tomas Aquino Creek in the wetlands by Sunnyvale’s Water Pollution Control Plant – and, now, Palo Alto’s Matadero Creek.