To understand California wildlife, researchers study roadkill. Here's what it tells us - Los Angeles Times
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To understand California wildlife, researchers study roadkill. Here’s what it tells us

Deer cross a four-lane street
Deer cross Main Street in Alturas, Calif., in 2019.
(Brian van der Brug / Los Angeles Times)
By Ryan FonsecaStaff Writer 
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Good morning. It’s Thursday, Oct. 12. Here’s what you need to know to start your day.

  • Here’s what roadkill data tells us about California wildlife
  • Space shuttle Endeavour’s rockets roll into L.A.
  • $50 tickets and everything else that’s new at Disneyland this fall
  • And here’s today’s e-newspaper

Roadkill data is shaping our understanding of California’s wildlife

I’ve written a decent amount about the effects our car-centric culture has on public safety, air pollution, housing and sprawl. But driving doesn’t harm just humans: collisions with cars kill massive numbers of wild animals every year.

Understanding just how much wildlife California drivers kill is giving researchers a sense of how some species’ populations are changing — and why.

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The Road Ecology Center at UC Davis attempts to quantify the effect our driving has on wildlife in its annual roadkill report. Its most recent findings, released in late September, point to “excessive rates of traffic collisions” as one possible factor in the population decline of some of the Golden State’s iconic wildlife.

(Fair warning: there are images of dead animals in the report.) The 2023 report also maps out roadkill hot spots across the state. But it’s much easier to spot the few regions where animals aren’t being regularly killed.

Dots of various colors are shown on a map of California.
A map shows roadkill reports across California for a variety of species from 2009 through 2022.
(Road Ecology Center at UC Davis)
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Researchers compiled reporting from 2009 through 2022, which showed that more than 173,000 species of mammals, birds, reptiles and amphibians were killed on roads across California. And that’s just the number of deaths reported by state agencies, by the public to an online database and to insurance companies. The actual death toll is higher, since not everyone who hits or kills an animal with their car reports the collision.

Fraser Shilling, director of the Road Ecology Center, said one purpose of the report is to identify “looming threats, in some cases before they become significant.” He explained another reason the roadkill report is so important:

“[California] doesn’t monitor wildlife populations very well… one way to do that is to monitor their deaths, unfortunately, but it helps give us an idea of where the wildlife populations are heading.”

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One of the key findings from the latest report is that the number of mule deer killed on state roads fell by 10% annually over the last seven years. That may seem like a good thing, but that would be giving drivers too much credit. The report indicates that the mule deer population is shrinking, meaning there are fewer for drivers to potentially strike.

The number of coyotes killed fell as well, which also points to population decline, the report states. That was surprising, Shilling said, because of how well coyotes have adapted to human-built environments. And taken together, those population decreases are a cause for concern, he explained:

“Deer and coyote are really quite different in their behaviors, what they eat, [and] their place in the ecosystem. The fact that they both went down is troubling because it suggests a larger ecological problem.”

And fewer deer and coyotes have a ripple effect on California’s mountain lions, which eat both species.

“There’s just fewer of their prey to find, so they have to move longer distances to find them,” Shilling said. “If they move longer distances, they’re going to cross more roads and there’s more chance they’re going to be hit by a car.”

Traffic collisions are a primary source of human-caused wildlife deaths, Shilling noted. Earlier this year, he mapped out fatal collisions of mountain lions, reporting that drivers were killing the pumas faster than they can reproduce.

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And of course Los Angeles’ own beloved celebrity cougar, P-22, was euthanized last December, in part due to injuries he suffered after being hit by a car.

California and other states are adopting some solutions to keep animals off roadways, including fencing, and safe crossing sites, such as the wildlife bridge under construction across the 101 Freeway in Agoura Hills.

Last year, Gov. Gavin Newsom signed into law the Safe Roads and Wildlife Protection Act, which directs Caltrans to make wildlife protections a priority when it plans new road projects.

Another solution noted in the Road Ecology Center’s report: lowering speed limits considerably in state parks and other roads that run through wildlife habitats.

Shilling said investments such as crossings and fencing would have been more impactful 20 years ago; the solutions we implement now “have to be more rigorous.”

For him, that means rethinking “how we’re driving and whether we drive at all,” especially since our culture centered on driving our cars mostly everywhere and mostly at our own discretion “is one of the biggest causes of environmental degradation in the world.”

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“It’s just like climate change,” Shilling said. “You have to start to make these choices. If you want to protect the environment — for your own generation or for future generations — the things you have to do are becoming more significant.”

Today’s top stories

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An area resident gets her photo taken by one of two large solid rocket motors being moved on Figueroa Street in Los Angeles.
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And finally ... from our archives

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On this day 25 years ago, college student Matthew Shepard died several days after being beaten, lashed to a fence post and left to die by two men in Laramie, Wyo., who later espoused anti-gay sentiments. Shepard’s sexual orientation was believed to have motivated the attack, and his death contributed to the expansion of federal hate crime legislation.

Have a great day, from the Essential California team
Ryan Fonseca, reporter
Elvia Limón, multiplatform editor
Kevinisha Walker, multiplatform editor
Laura Blasey, assistant editor

Check our top stories, topics and the latest articles on latimes.com.

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Ryan Fonseca

Ryan Fonseca writes the Los Angeles Times’ Essential California newsletter. A lifelong SoCal native, he has worked in a diverse mix of newsrooms across L.A. County, including radio, documentary, print and television outlets. Most recently, he was an associate editor for LAist.com and KPCC-FM (89.3) public radio, covering transportation and mobility. He returns to The Times after previously working as an assistant web editor for Times Community News, where he helped manage the websites and social media presence of the Burbank Leader, Glendale News-Press and La Cañada Valley Sun. Fonseca studied journalism at Cal State Northridge, where he now teaches the next generation of journalists to develop their voice and digital skills.

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