A Tale of Two Tunnels

It’s official. After years of monitoring at the Harbor Boulevard Wildlife Underpass, the results are in…and the news is good!

The underpass was built in 2006 to maintain a viable means for wildlife to move between habitats on both sides of Harbor Blvd., helping to sustain the Puente-Chino Hills Wildlife Corridor. Now, the underpass is a big success, with many different species of wildlife using it on a regular basis to cross under Harbor Blvd. By doing so, these animals avoid the risk of becoming roadkill while crossing Harbor Blvd. at the road surface.

The most interesting findings from the long-term monitoring study were that (1) mule deer used the new underpass almost immediately, which is unusual compared to other underpasses studied, and (2) that coyote roadkill had decreased by approximately two-thirds compared to before the underpass was built. In addition to mule deer and coyote, which were frequent users of the underpass, other species observed included striped skunk, raccoon, and desert cottontail rabbit, and even bobcats which were rarely detected until the last part of the study. Researchers at CSU Fullerton, who conducted the study, believe that some of the wildlife, especially coyotes, may have taken a few years to “learn” to use the underpass, and now that they have done so are not becoming roadkill as much as they were in the past.

Further west, along Colima Road, there is another underpass; however, this one has existed for a long time as it was built for oil production transport before the area became a Preserve. A previous study conducted in 2001 and 2002 found that many different wildlife species also used this underpass, similar to those in the Harbor Blvd. Underpass, with bobcat, coyote and mule deer being the most frequent. This study also found that wildlife use of the Colima Underpass did not change substantially after the area was opened to public use and the underpass was part of the public trail system.

The Colima Underpass is being studied again this year by the Habitat Authority in an effort to see how wildlife activity and usage has changed over the last decade of public use and habitat restoration efforts, and to provide more baseline data for other projects that may occur in the area. But preliminary results indicate that wildlife usage remains high, with coyotes and bobcats seen as frequent visitors to the underpass, as well as skunks and rabbits. The maintenance of this underpass may be critical to maintaining habitat connectivity on both sides of Colima Road, and allowing for wildlife movement with fewer roadkill.