Mule Deer Use California's First Wildlife Overcrossing in Siskiyou County

On March 24, motion-activated cameras captured three mule deer crossing the under-construction wildlife overcrossing on U.S. 97 near Mount Shasta, Siskiyou County. The same monitoring recorded a bobcat and additional wildlife using the structure while crews were still on site.

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U.S. 97 has recorded frequent wildlife-vehicle collisions, with over 50 deer and 16 elk killed between 2015 and 2020. California’s Department of Transportation (Caltrans) is installing wildlife bridges and tunnels statewide to reconnect habitats and cut fatalities. Although most of the planned structures are in Southern California, the first documented wildlife use has occurred in the northern project.

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Bridge components include a concrete tunnel, roughly 3 miles of 8-foot fencing, and an overpass slated to open later 2024. Target species are mule deer, Rocky Mountain elk, gray wolves, black bears and mountain lions.

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Caltrans officials say the overcrossing is designed to give animals a safer route and lower vehicle-collision rates. The UC Davis Road Ecology Center stresses the corridor’s high mortality and the need for structural mitigation. Program managers note early wildlife use validates the bridge’s placement. Officials anticipate long-term ecosystem health improvements as species regain access to previously isolated habitats.

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Camera footage confirmed three mule deer crossing on March 24, followed by a bobcat and other wildlife.

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The structure directly addresses documented wildlife fatalities and aims to restore habitat connectivity, while reducing collision risk for motorists. Reduced collisions also improve travel reliability for motorists.

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Only short-term observations are available; long-term impacts on collision rates and species populations remain unmeasured.

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• “While the contractor is still completing final touches, it’s incredible to see wildlife already embracing the new structure, even with workers still in the area. In addition to deer, a bobcat and other wildlife have also been spotted using it,” — Caltrans District 2, Facebook post

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• “This wildlife overcrossing was designed to provide animals with a safer way to cross the highway while helping reduce wildlife-vehicle collisions for motorists traveling through the corridor.” — Caltrans District 2, Facebook post

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• “There’s truck traffic that goes through there, and they don’t slow down. They hit whatever’s on the road, so a lot of deer and elk were getting killed.” — Fraser Shilling, director, UC Davis Road Ecology Center

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• “Wildlife crossings restore ecosystems that had been fractured and disrupted. They reconnect lands and species that are aching to be whole. I believe these crossings go beyond mere conservation, toward a kind of environmental rejuvenation that is long overdue,” — Wallis Annenberg, donor

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The Siskiyou County overcrossing will open later this year, with monitoring to evaluate wildlife movement and collision rates. The Wallis Annenberg Wildlife Crossing on the Ventura Freeway is also slated for a 2024 opening, extending the statewide connectivity network.

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