Skip to main content
U.S. flag

An official website of the United States government

Cats can find curious ways to navigate the human environment. USGS Western Ecological Research Center ecologist Erin Boydston has been studying how large wildlife like bobcats and mountain lions deal with the suburban sprawl of Southern California.

Dr. Erin Boydston (Public domain.)

One area of focus is how animals cross roadways -- since roads and their vehicle traffic are obvious barriers to wildlife movement.

On a previous project for the California Department of Transportation (Caltrans), Boydston and her team attached GPS-tracking collars on wild bobcats (Lynx rufus) to study where bobcats were crossing California Highway 71, near the City of Chino Hills. They also deployed camera traps at underpass structures along the highway, and photographed bobcats and other wildlife moving underneath CA-71.

Camera traps are "virtual traps" -- consisting of a motion-triggered camera to capture evidence of wildlife passing a certain location. They are frequently used to study wildlife species wary of people. In fact, one of Boydston's camera traps found the first evidence of the now-famous P-22, "the Hollywood lion".

The results from CA-71 were fascinating, showing how bobcats crossed CA-71 at various points to travel from seemingly divided fields of habitat. In general, they found good agreement between GPS movement data and locations of underpasses.

But there were a few mysterious gaps.

The GPS tracking data also showed bobcats crossing CA-71 at locations where wildlife fencing was in place along the highway to prevent animals from getting hit by cars. These locations did have some culverts -- pipes and tunnels intended to allow rain and flood water to pass under a roadway -- though not the types of culverts that wildlife were known to use.

So Boydston and her team took another look -- and they finally captured a clue.

Recently, Boydston started a camera-trap project for Chino Hills State Park, in the same area as the Caltrans CA-71 project. "That's when we went back and installed camera traps at culverts we suspected bobcats had used," Boydston says. "We had GPS data suggesting that bobcats were likely using a 'capped' culvert -- one that makes a right angle underground and emerges like a stovepipe, coming straight up.”

The new camera traps delivered photographic confirmation.

Time-elapsed photos of a bobcat in Chino Hills crossing CA-71
Time-elapsed photos of a bobcat in Chino Hills crossing CA-71 as part of a USGS study. Playback not in real-time and speed/pace has been altered. (Credit: U.S. Geological Survey. Public domain.)

These images was taken on December 25th, 2013 -- Christmas night -- but as is often with research, it took a while before researchers could sift through the mass of data and images. It was only recently that Boydston came upon this photograph -- evidence that bobcats occasionally use this capped culvert to move under CA-71.

"Well this is our first image documenting a bobcat emerging from it,” says Boydston. "It was like Santa coming through the chimney -- but apparently a day late!"

Amazingly, even with the amount of people in Los Angeles, Orange County and other urban centers, Southern California remains an important landscape for wildlife species and a living research lab to study urban wildlife interactions. So with a culvert-crawling bobcats and a Hollywood mountain lion to her credit, who knows what Boydston's camera traps will capture next?

Dr. Boydston is interested in your observations! If you get a photo of a bobcat in Southern California -- especially kittens -- please share it with us via

A bobcat captured by remote camera
A bobcat captured by remote camera, near Chino Hills, CA. (Credit: U.S. Geological Survey. Public domain.)

-- Ben Young Landis