Coyotes are the likely culprits in the bloody beheadings of seal pups in Northern California, researchers said.
“I think it’s something exciting. It is a predator-prey relationship that is developing. It’s nature happening,” Sarah Codde, a National Park Service marine ecologist at Point Reyes National Seashore, told Mercury News of the discovery.
Since at least 2015, headless carcasses of seal pups had been washing up on Northern California beaches, Sarah Grimes, marine mammal stranding coordinator at the Noyo Center for Marine Life, told the Los Angeles Times.
The attacks focused primarily on harbor seals at MacKerricher State Park in Mendocino County, Grimes said.
“I felt like a marine mammal CSI, seeing all the dead pups with their heads torn off, and I thought, ‘What the hell did that do?’” Grimes added of the years-long mystery.
A coyote and an elephant seal at Point Reyes National Seashore. A. Kopshever / National Park Service
By 2020, then-unidentified predators were also tearing off chunks of the fins of 300-pound weaned elephant seal pups at Point Reyes National Seashore, according to Mercury News.
Experts were initially baffled by the gruesome findings and wondered if it could be the work of humans or even a skin disease among seals, Codde explained.
The problem seemed to dissipate in 2020 and 2021, but weanling pups with fin bites showed up again this year, Codde told the outlet.
Finally, Codde enlisted the help of Frankie Gerraty, a doctoral student at the University of California, Santa Cruz, who set up a camera at Point Reyes and caught the attackers in the act.
“The coyote was really struggling to pull it and the seal was trying to get loose. We captured it for about six minutes as the coyote pulled and bit, and then the seal ran away, the coyote grabbed it again, and then they went off screen,” Codde said of the footage.
In the fall, Gerraty also installed a camera at MacKerricher, where they captured images of a coyote attacking a seal and “decapitating it,” he explained.
The elephant seals lie on a beach, where some of them disembark to have their young. Anadolu Agency via Getty Images
“Coyotes are underappreciated predators in coastal ecosystems, and marine mammals are the largest, most calorie-dense nutrient parcels in the ocean and, really, anywhere in the world,” Gerraty added.
Teams still don’t know why coyotes only eat the heads of pups, or why they only attack the fins of elephant seals.
“In all the pups we saw with injured fins, there were no other bites anywhere else on the body. We didn’t know why they would do that, what the purpose was, what the nutritional value is,” Codde explained.
“Maybe they think it’s a carcass, and then they go there, take a bite, realize it, and run away,” Tali Caspi, a doctoral student at the University of California, Davis, who studies coyotes, told Mercury News.
Seals and sea lions may have felt more comfortable having pups on beaches, rather than sandbars, as ranchers have mostly driven away land-based predators, the outlet noted.
But now the coyotes are getting closer to the water.
“Everyone was fat and happy, and no one bothered them. Then populations of large predators started to increase and all of a sudden now there’s a killer in the mix,” Grimes said.
The coyotes are getting closer to the water. Anadolu Agency via Getty Images
Researchers are already seeing fewer harbor seal pups in MacKerricher Park, he added.
“Harbor seals are quite skittish. Maybe the smarter ones are realizing that they haven’t been able to breed for the last few years and are choosing a different site,” she speculated.
The harbor seal count at Point Reyes could also be declining.
“More research definitely needs to be done on the state’s harbor seal population so we can see if they are moving into different areas,” Codde confirmed.
“If seals have to find new locations because of coyotes, we need to be aware of that and protect those areas from human disturbance,” he added.
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Source: vtt.edu.vn