Trail cameras recently caught three mule deer strolling over what researchers are calling California's first state-highway wildlife overcrossing in Siskiyou County. The structure arches above a particularly deadly stretch of State Route 97 where vehicle collisions have killed dozens of deer and elk. Conservation advocates say the early traffic on the bridge is a strong sign that purpose-built crossings and fencing can reconnect fractured habitat and cut down on crashes.
According to the Los Angeles Times, the mule deer were photographed on the new overpass in late May and are the first confirmed animals to use it. The outlet cites Caltrans data showing that more than 50 deer and 16 elk were struck and killed along that section of highway between 2015 and 2020. Officials say the crossing is nearing completion and will be paired with barrier fencing designed to guide animals to safe passage points.
What the overcrossing includes
The Grass Lake overpass is a vegetated span built to blend into the surrounding landscape, with local reporting describing it as roughly 100 feet long and 140 feet wide and sized to feel comfortable to wildlife, according to SFGATE. Project filings and planning documents summarized by California Highways show the broader effort also includes several miles of exclusionary fencing, jump-outs, cattle guards and a concrete box culvert to create alternative undercrossings. Engineers say that the combination is meant to steer wildlife toward the overpass and away from fast-moving traffic.
Why early crossings matter
Shilling and Caltrans officials say the Grass Lake crossing, together with fencing, will be vital for mule deer, elk, mountain lions, black bears and even a local gray wolf pack that move through the corridor. Because animals often need time to discover and trust new structures, researchers see this early use by deer as an encouraging first step.
Part of a bigger statewide push
The Grass Lake project is one of several wildlife crossings now under construction across California. Among them is the much larger Wallis Annenberg Wildlife Crossing over US-101 in Agoura Hills, which Caltrans lists as a $114 million, vegetation-topped span slated to open later this year. State transportation officials and conservation partners say pairing overpasses with long stretches of fencing is proving to be the most effective way to reduce wildlife-vehicle collisions and reconnect fragmented ranges.
What comes next
One of nearly 100 motion-triggered cameras set up around the Grass Lake project recorded the three mule deer crossing in late May, SFGATE reports. Researchers plan to keep reviewing footage to see which species adopt the new route over the coming seasons. The UC Davis Road Ecology Center's 2024 roadkill report found that tens of thousands of deer and hundreds of mountain lions are killed on California roads each year, underscoring the stakes for crossings and fencing projects. Experts say long-term maintenance and monitoring will be key to determining whether this early success at Grass Lake translates into fewer collisions and healthier wildlife populations.
