A section of Interstate 280 on the Peninsula has been the deadliest highway in the state for wildlife being struck by vehicles in the past five years, according to a new report by University of California, Davis.

The Road Ecology Center of UC Davis based its report on roadkill hotspots on California highways on 44,000 wildlife-vehicle collisions from California Highway Patrol and 65,000 reports sent into the California Roadkill Observation System between 2009 and 2020.

According to the report, the stretch between San Bruno and Cupertino on I-280 has consistently had the highest rate and cost of WVCs in California. Annually, WVCs on 31 miles of I-280 cost an estimated $5.8 million in damage.

WVC are defined as incidences in which animals pass roadways and pose a threat to driver safety, reads the report. Not only can the driver face injuries or car damage from hitting an animal or swerving to avoid them, busy intersections can severely impact the wildlife populations that surround them.

Within the past five years, 302 mountain lions were involved in reported crashes, for example. The report notes that this figure does not represent all mountain lions killed on highways and should only be considered as the minimum, as there is no formal requirement for residents to report roadkill incidents.

The cost of wildlife-vehicle collisions on Bay Area freeways is detailed in this graphic from the UC Davis Road Ecology Center’s 2021 WVC report. Portions in red indicate areas with the greatest annual expense per mile of roadway. (Image courtesy of UC Davis Road Ecology Center via Bay City News)

Big cats need big protections

The California Department of Fish and Wildlife is currently reviewing mountain lions as a potential candidate under the California Endangered Species Act and already has conservation plans to protect the 2,000 to 3,000 wild cats still living in the states.

“Like most species at the top of the food web, mountain lions are especially vulnerable to WVC because they move around a lot and cross roads and highways. Mountain lions are important ecologically because they are the only large, widespread predator in most California ecosystems,” reads the report. “They are also important socially, with great interest in their well-being in Southern California and Bay Area urban regions.”

“Wildlife-vehicle collisions continues to be an under-recognized and under-reported threat to wildlife populations and to drivers in certain areas,”

UC Davis report

The report also notes that roadkill incidents should not only be framed as an environmental issue, as these collisions can pose a real economic impact. The report estimates that WVC costs state residents $1.1 billion to $2.2 billion within the last five years.

The hope with this study, the Road Ecology Center wrote, is to identify specific parts of highways that are most likely to have WVCs to assist Caltrans and other transportation agencies in developing focused mitigation strategies.

Some solutions with the best success rates include reducing speed limits in areas with wildlife presence and building fencing or passageways for animals to safely cross above or below the highway, according to the report.

“Wildlife-vehicle collisions continues to be an under-recognized and under-reported threat to wildlife populations and to drivers in certain areas,” reads the report. “Even common species like mule deer may be experiencing unsustainable levels of mortality. The state should spend its ample transportation funds to solve this traffic safety and sustainability issue.”

Mitigation benefits could outweigh costs

So how much would it cost to implement these mitigation strategies? Less than what WVCs have already cost the state in the past 10 years, the report estimates.

Readers can download the UC Davis Road Ecology Center’s report.

Fencing in 1,275 miles of high-risk highway strategies would take a little over $175 million, meaning the value of reduced crash coss would exceed mitigation efforts in 10 years, according to the report.

But the report calls on legislators to take concrete steps to investing in WVC-reduction projects quickly and with transportation funds, not from limited wildlife, parks and environmental budgets.

Additionally, Road Ecology Center researchers encourage Californians to anonymously report roadkill sightings to contribute to more accurate data analyses.

“Monitoring wildlife movement and mortality is critical for improving wildlife connectivity and survival of wildlife species in the face of the combined threats they face, such as transportation systems, climate change, rodenticides, and habitat loss,” the report summarizes.