They’re one shell of a menace.

An invasive species of abandoned pet turtles is wreaking havoc in city parks — pushing out native animals and potentially exposing visitors to Salmonella, according to experts.

The population of red-eared sliders is booming in Central Park and at Harlem’s Morningside Pond, where they’ve been snapping up grub and hogging turf from native turtles, said Allen Salzberg of the nonprofit New York Turtle and Tortoise Society.

“They grow large and they’re taking food and [sun] basking space from native turtles,” said Salzberg. “They’re all over.”

The murky pond is crawling with the reptiles because they were dumped there by irresponsible pet owners, he said. The animals hail from the Gulf of Mexico, and are the most popular turtle in the American pet trade.

“People think, ‘Oh, I don’t have to feel guilty, I’ll put them in the wild,’ but unfortunately there’s no such thing as wild pond in Central Park,” he said.

Unlike native snapping turtles, the animals also “carry Salmonella,” which can put park-goers who touch them at risk of illness, he said.

Visitors to the park on Sunday demanded that city officials help curb the space-hogging critters.

“Someone should be controlling this,” said Mark Zouiyen of the Upper East Side. “There’s an ecosystem here and you can’t disrupt it.”

Wayne Shelby, who was walking his two basset hounds in the park, added, “It’s a strange thing. It’s like the iguanas in Florida — they’ve taken over.”

More than 52 million red-eared sliders were legally exported from the United States between 1989 and 1997, many of them to China, according to National Geographic, which first reported New York’s turtle invasion.

Many more are sold on the black market through street vendors and websites.

“The solution is to catch the turtles and euthanize them — then wait to see if the native turtles come back,” Salzberg said.

The red-eared sliders, who now live in the wild in nearly every state, including Hawaii, got their name by the red markings on their head that resemble ears.

They are routinely ranked among the world’s hundred worst invasive species by the International Union for Conservation of Nature, according to National Geographic.

The Parks Department said people should “never release unwanted pets into any city park.”