These California highways are hot spots for roadkill — but data points to falling population

Data from an annual UC Davis report shows that wildlife is being hit less frequently on California highways, which could suggest an overall decline in certain animal populations.

Mule deer and coyote populations may be decreasing throughout the state, roadkill data from the Sept. 25 Road Ecology Center report indicates.

From 2016 to 2022, more than 30,000 wildlife-vehicle collisions that involved large mammals were reported to the California Highway Patrol or through the California Roadkill Observation System, according to the research. New funding is being used in the state to prevent roadkill incidents and create roadside wildlife fencing. UC Davis Road Ecology Center is collecting data that will help locate and strategically design fencing crossings.

Coyote and deer population decline in California

Fewer collisions with mule deer “indicate a roughly 10% population decline” annually for seven years, according to a news release. Over the same time period, it states, the population decline was 5% per year for coyotes.

Although wildlife-traffic collisions can be an indicator of declining wildlife populations, there are other factors that come into play. Below are external factors to consider, according to the study:

▪ Drought

▪ Habitat degradation

▪ Changes in reporting rates

▪ Fencing installation for crossing

Researchers suggest declines in mule deer and elk populations are greatest in areas that are undergoing “rapid development and traffic increases,” like the Bay Area and the Sierra Nevada foothills. However, the California Department of Fish and Wildlife doesn’t “recognize wildlife-vehicle conflict (as) a primary cause of deer population decline.”

State Farm Insurance reported an estimate of around 22,000 claims a year due to deer collisions in California.

Mountain lions and bears are also vulnerable populations. The animals have large home ranges which require them to move frequently across roadways for food and water.

According to the study, both animals have seen a 10% increase in collisions between 2016 and 2022.

California highway collision hotspots

The Road Ecology Center at UC Davis mapped out stretches of 15,000 miles of California state highways that are considered wildlife-vehicle conflict zones. There are 615 statistically significant collision hot spots in the state, according to the study.

Below are some reported hot spots for roadkill:

▪ Bay Area: Interstate 680, I-280, Highway 17

▪ Sacramento region: Highway 49, I-80, Highway 50

▪ Central Sierra: Highway 108, Highway 88, Highway 4

▪ Central Coast and Southern California: I-405, Highway 101, Highway 154

What is California doing about it?

California, in comparison to other states in the country, is behind when it comes to wildlife fencing, according to the report.

But it’s taking action to catch up. The Legislature approved nearly $1 billion in funding through AB 2344 for the conservation, management and protection of wildlife.

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