Coyotes are the likely culprit behind seal beheadings in Northern California, researchers say.
“I think it’s an exciting thing. It is an evolving predator-prey relationship. It’s just nature happening,” Sarah Codde, a marine ecologist with the National Park Service at Point Reyes National Seashore, told the Mercury News of the discovery.
Since at least 2015, headless seal pup carcasses have been turning up on Northern California beaches, Sarah Grimes, marine mammal stranding coordinator with the Noyo Center for Marine Life, told the Los Angeles Times.
The attack was primarily focused on seals at MacKerricher State Park in Mendocino County, Grimes said.
“I was like CSI marine mammals, looking at all the dead puppies with their heads ripped off, and I was like, ‘What did he do?’” Grimes added to the mystery over the years.
A seal and seal at Point Reyes National Seashore. A. Kopshever / National Park Service
By 2020, the then-unknown predator also took a chunk of the fin of a 300-pound elephant seal pup at Point Reyes National Seashore, according to the Mercury News.
Experts were initially baffled by the gruesome discovery — and wondered whether it might be the work of humans or a skin disease among the seals, Codde explained.
The problem appeared to disappear in 2020 and 2021, but weanlings with fin bites are showing up again this year, Codde told the outlet.
Eventually, Codde enlisted the help of Frankie Gerraty, a doctoral student at the University of California, Santa Cruz, who installed a camera at Point Reyes and caught the attacker in the act.
“The coyote was really struggling to pull it, and the seal was trying to pull away. We caught it for about six minutes of the coyote pulling and biting, and then the seal would let go, and the coyote would get it back, and then they were off the screen,” Codde said of the footage.
In the fall, Gerraty also set up a camera in MacKerricher, where they captured footage of a coyote attacking a harbor seal and “decapitating it,” he explained.
Elephant seals lie on the beach, where some of them come ashore to pick up their young. Anadolu Agency via Getty Images
“Coyotes are underappreciated predators in coastal ecosystems, and marine mammals are the largest and most calorie-rich bundle of nutrients in the ocean, and really anywhere in the world,” Gerraty added.
The team still doesn’t know why the seals only eat the pups’ heads — or why they only attack the seals’ fins.
“For all the puppies we saw with injured fins, there were no other bites on other parts of the body. We don’t know why they do that, what the purpose is, what the nutritional value is,” explained Codde.
“Maybe they think it’s a carcass, and then they go over there, and they bite, realize and run away,” Tali Caspi, a doctoral student at the University of California, Davis, who studies coyotes, told the Mercury News.
Seals and sea lions may become more comfortable having pups on beaches – rather than sandbars – as terrestrial predators have mostly been driven out by breeders, the outlet said.
But now the coyote is encroaching closer to the water.
“Everyone is fat and happy, and no one bothers them. Then the population of large predators started to increase, and suddenly, now, there are killers in the mix,” Grimes said.
The coyote intruded closer to the water. Anadolu Agency via Getty Images
Researchers are already seeing fewer harbor seal pups at MacKerricher Park, he added.
“The harbor seals are quite restless. Maybe the smarter ones realized that they failed to pupate over the past few years, and they chose a different site,” he speculated.
The harbor seal count at Point Reyes may also be declining.
“There’s definitely more research that needs to be done on what the statewide population looks like for harbor seals so we can see if they’re moving to different areas,” Codde confirmed.
“If harbor seals have to find a new location because of coyotes, we need to be careful and protect the area from human disturbance,” he added.
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Source: thtrangdai.edu.vn/en/
