Santa Cruz, Calif. – Whether it's ice cream, a greasy hamburger, or a heap of french fries, everybody loves fatty foods. For coyotes, that meal is a blubbery seal pup, according to a new study led by UC Santa Cruz scientists.
A paper published on February 12 in the journal Ecology details how the researchers used motion-triggered cameras placed at MacKerricher State Beach, north of Fort Bragg, during harbor seal pupping season in the spring of 2023 and 2024. Led by UC Santa Cruz Ph.D. student Frankie Gerraty, the team recorded three instances of a coyote dragging a baby harbor seal away from the beach and devouring it.
The coyotes often ate the brain first, and removed the seals' head to get to it. Scientists combing the sand dunes overlooking the rookery have found the bodies of over 50 pups hunted this way since 2016. "I had a hunch it was coyotes," Gerraty said. "Terrestrial wildlife that eat seafood are a major focus of mine, and we know that coyotes are very adaptable."
The mystery began when study co-author Sarah Grimes, of the Noyo Center for Marine Science, began noticing seal-pup carcasses that were dragged to the same spot and eaten. "There was consistency," she said. "They weren't scattered here and there."
Black bears, bobcats, and mountain lions all call the region home, so it was not immediately clear who was responsible. Tracks and droppings found nearby eventually led Grimes to suspect coyotes, but Gerraty secured proof when he captured them on video.
"I immediately told Sarah," he said. "For six years, she had been building up so many ideas about what it could be and how it was happening."
Natural behavior
Many of us had our first impression of the species through Wile E. Coyote, a scraggly cartoon character who is locked in a fanatical pursuit of the Road Runner. Gerraty does not want his research to fuel this negative perception of the species. "Coyotes have a PR problem," he said. "A lot of people do not like coyotes, but everybody loves baby seals."
This is a natural interaction between two native species, Gerraty explains. And while California coyotes might have hunted harbor-seal pups for centuries, this study is the first to empirically confirm the phenomenon that researchers first started noticing in 2016.
Most of the seal pups were as big as their canine hunters, and the coyotes would spend several days feasting on them, the study reports. Also, the pups might be an important springtime food source for species beyond coyotes: Vultures, ravens, and bald eagles were also found to have fed on their carcasses.
Adaptation to predation
MacKerricher State Beach is not the only place where coyotes hunt seals. Naturalists gave the researchers photos of coyotes hunting harbor seal pups at Drakes Estero and Bolinas Lagoon in Marin County. Other scientists have documented coyotes hunting seals in Washington state and Massachusetts, But this study provides some of the most detailed accounts of this practice.
Land-based predators might influence where seals raise their young. The number of harbor seals at MacKerricher State Beach has decreased since 2018, and many of the ones that remain keep their pups on rocky outcrops that are difficult to reach.
Centuries ago, when wolves and grizzly bears filled California, seals opted to raise their young on islands. Only recently did seal rookeries become common on the mainland. "There are a few case studies that suggest the absence of large carnivores along our coastline has created space for marine life," said Gerraty.
He points to recent research that found penguins in Patagonia moved some breeding sites away from islands after settlers decimated puma populations. Now the cats are recovering, and they have begun hunting penguins that moved to the mainland.
This research was supported by grants from the Point Reyes National Seashore Association Neubacher Marine Science Fund, Explorers Club Exploration Fund, Western Society of Naturalists Rafe Sagarin Fund, Tomales Bay Foundation Student Research Award, Rebecca and Steve Sooy Graduate Fellowship, Achievement Rewards for College Scientists Fellowship, and a National Science Foundation graduate-research fellowship awarded to Gerraty.
