by Finding dead seals along the California coast is nothing new. The marine mammals become sick, stillborn or even washed ashore after being fatally struck by a boat.
But decapitated seals? That was new to North Coast ecologists – even those who study stranded marine life.
Repeatedly since at least 2015, the mysterious — and gruesome — deaths have continued to occur, mostly involving harbor seal pups at MacKerricher State Park, not far from Fort Bragg in Mendocino County, according to Sarah Grimes, marine mammal trade coordinator and educator at MacKerricher State Park. Noyo Center for Marine Life in Fort Bragg. The killings weren’t happening en masse, but up to a dozen or so carcasses had been found each of the past few years, she said.
Now researchers have solved the decades-long mystery of the headless seals: coastal coyotes, a finding first reported by the Mercury News.
In a wildlife camera set up last year near the seal rookery in MacKerricher State Park, ecologist Frankie Gerraty caught a coyote decapitating its prey, confirming the hypotheses of many researchers about the forgiven seal carcasses.
“We had a spectacular capture of a coyote that dragged a fresh-killed seal into the [camera view]and for five minutes to go on[ing] take his head off,” said Gerraty, a doctoral student in the department of ecology and evolutionary biology at UC Santa Cruz.
That groundbreaking video has not yet been published or shared publicly as researchers work to further understand the predator-prey relationship, Gerraty said. He hopes to publish their research on the coastal coyotes in a future paper, describing how the species has become not only a beach scavenger but also a beach predator.
Gerraty’s cameras confirmed this new predator-prey relationship at Point Reyes National Seashore in Marin County, he said.
Gerraty began hearing about the decapitated harbor seals while doing so research on the coastal coyotediet; he said it was well written that they would spare seals that were already dead.
Grimes was working to understand the phenomenon – only with hints, not with any confirmation.
“I went from a domestic dog to a bald eagle … what is this doing?” she said.
But she was stuck.
When Gerraty started hearing about the decapitated seal carcasses, he said, “it was scary that it could be coyotes because we already knew they spend a lot of time on beaches.”
But when he saw one of the headless seals next to him, he thought that the cut along the neck was too clean to be the work of a coyote, and he worried that it might even be human.
Then the video footage proved him wrong.
“We know, 100%, that coyotes are responsible for some seal kills in a few locations,” Gerraty said.
“Obviously it’s terrible, but at the same time … coyotes and harbor seals are native species,” he said.
Coyotes are making a comeback in the Bay Area and Northern California after decades of decline by ranchers and ranchers, who poisoned and hunted the wild rabbits.
“As these predators recover, it’s really interesting to think about how the ecological relationship may or may not be recovering,” Gerraty said. He said it wouldn’t surprise him that, historically, coyotes have hunted seals, but it has never been documented.
It’s important to nurture and understand this native habitat and natural life cycle, Grimes said — and not think of coyotes as savage or ruthless.
“This is really the balance of nature,” Grimes said. “The coyote is not a villain. It’s a part of the ecosystem that has been missing for several years.”
It’s not yet clear why the coyotes are only asking for the seals’ heads and then leaving the bodies for other scavengers, but Gerraty has his doubts.
“In my opinion the brains are quite nutritious compared to many other seal parts. Blubber can be pretty hard to get through,” he said.
But those questions will continue to drive Gerraty’s research into how widespread this predation is and what it might mean for each species.
“It could have interesting implications for both the seals and the coyotes,” he said. He doubts the coyotes’ current hunting patterns would have any major effect on the harbor seal population, but he said it could affect where they congregate and breed.
“If these seals are realizing that some of these sites are dangerous … they may choose to give birth and ‘pull out’ elsewhere,” Gerraty said. Depending on where they move, he said, it may be less suitable for pup development or food sources, which could have longer-term effects.
Because of the many unknowns, Grimes said, it’s important for people to continue reporting stranded sea creatures — that is, dead on the beach or alive but unable to return to shore. of the water — to the West Coast Marine Beach Network, that is. is run through the National Oceanic and Atmospheric Administration.
“We learn so much about ocean health,” she said, “through those stranded animals.”
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This story originally appeared in the Los Angeles Times.
