Great Gray Owls Use Roads in Yosemite at Their Peril

New research in Yosemite National Park aims to help prevent collisions between vehicles and rare great gray owls

Text and photos by Vishal Subramanyan
Wildlife Science
Dec 17, 2025

A great gray owl hunts within Yosemite National Park (above). Another (below) met its fate on state Route 120 outside the park. Biologist Dustin Garrison (bottom) scans a park meadow for owls with GPS telemetry in July 2023.

IN THE HIGH-MOUNTAIN MEADOWS OF EASTERN CALIFORNIA, a male great gray owl perches beside a road within Yosemite National Park. He is laser-focused on his prey: a rodent moving in the grass on the other side of the road. As he takes off, flying just inches over the pavement, a car speeds by, narrowly missing the owl.

Although this one survived the close call, many owls are not as fortunate. With a habitat ranging from California’s northern Sierra Nevada south to Sequoia National Park, Yosemite’s great gray owls—typically smaller than other American great gray owls and favoring high-mountain snags over platforms or abandoned nests—were proposed as a genetically distinct subspecies in 2010. Estimates put remaining breeding pairs at fewer than 100. Since 2003, 23 known individuals have been struck by vehicles in the Yosemite region—at least 11 percent of the population.

An image of a great gray owl which had been recently struck by a car and killed.

“They’re one of the signature species of Yosemite,” says Heather Mackey, a Yosemite National Park biologist. “They’re a boreal species adapted to northern climates that are able to survive in Yosemite”—if they evade cars.

Dismayed by the death toll, scientists are trying to prevent these collisions. From March 2022 to March 2024, Yosemite partnered with the Institute for Bird Populations and the Teton Raptor Center to conduct a study of great gray owl movements in the park, particularly around roads and meadows. (I joined the field team in summer 2024 as a photographer to document the effort.)

Owls depend on Yosemite’s meadows: wet, open grasslands 3,000 to 8,000 feet in elevation that are surrounded by stands of old-growth mixed-conifer forest and rife with the birds’ favored prey, such as voles and pocket gophers. But these habitats are increasingly at risk.

“Humans are drawn to meadows,” says Dustin Garrison, a National Park Service biologist who served as a primary field technician on the study. “They’re beautiful. But that means we build roads through them and put development nearby—campgrounds, gas stations, lodges and so on.”

The scientists’ first step was the hardest: finding and temporarily capturing the owls to put trackers on them. Despite their size, with wingspans up to 5 feet, Yosemite’s great gray owls can be notoriously difficult to locate. “Sometimes we captured the owl within a half an hour,” Garrison says. “Other times we spent a week and a half with a massive effort and still couldn’t get them.”

The team initially hoped to tag as many as 10 owls, but due to logistical and budget constraints, they ultimately outfitted six with trackers. Amounting to less than 3 percent of a bird’s body mass, these specially designed backpacks consist of a lithium battery, an epoxy-encased GPS transmitter, short antennae and cord straps.

An image of biologist Dustin Garrison scanning for great gray owls with GPS telemetry.

Once a month, Garrison and colleagues trekked into the park with radio telemetry equipment to download the owls’ GPS signals, gaining insight into the birds’ habitat use, hunting patterns and proximity to roads. The team also used the data to find and observe the owls directly in the field and to survey vegetation in owl hot spots, with an eye toward future modifications that might deter owls from high-traffic habitat.

While analysis is ongoing, one big surprise was how much the owls use forested areas for hunting in addition to nesting. “The subspecies of great gray owls are known to be meadow specialists” due to an abundance of prey, Garrison says. “It shocked all of us how often some of the owls were using the forest to forage.”

Those forests, however, are under threat. Another early finding indicates that owls avoid high-severity burn areas during both breeding and nonbreeding seasons. As megafires increase in size and magnitude in California, with trees more susceptible to damage than grassy meadows, owls could lose more habitat.

Also surprising was that some owls seemed to favor dangerous roadside areas for hunting. “A lot of owl locations are really clustered along roads,” says Ramiro Aragon, a biologist with the Institute for Bird Populations. “It might be that roads run parallel to really good hunting habitat or that [park roads] cut through the middle of areas owls are already using. So it’s hard to say if they’re attracted to roads or just caught in between.”

During the April to June breeding season, when hunting increases, scientists regularly tracked adult owls closer to roads on a more frequent basis. This puts the birds at increased risk of vehicle strikes during an especially vulnerable period.

The data also revealed a concerning overlap between owl activity and traffic peaks. In the breeding season, nesting owls were most active just after sunset and between 4 and 6 a.m. That early hunt coincides with morning rush at the park, which allows public entry without a reservation before 6 a.m. With an average of 4 million visitors a year, Yosemite was the nation’s sixth most-visited park in 2024.

Going forward, “We can use this data to inform the timing of the reservation system so we’re not creating an artificial push of traffic right around peak owl activity,” Mackey says.

Once scientists finish their analysis and publish their findings, they hope to enact other changes to protect the owls. Potential strategies include reducing speed limits from 40 to 25 mph along key corridors and modifying vegetation to make roadside habitat less attractive.

“There’s two ways to approach [changes],” Garrison says. “You either modify human behavior, or you modify wildlife behavior.”

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