Wild pigs are a mix of wild boars and domestic swine that are spreading across Canada’s provinces and leaving devastation in their wake.

Researchers studying wild pigs’ distribution in Canada for the first time have found a rapid expansion in their range, which is increasing by 9% each year.

“Wild pigs are ecological train wrecks. They are prolific breeders making them an extremely successful invasive species,” said Ruth Aschim, a Ph.D. student at the University of Saskatchewan who led the research, in a statement. The findings were published in Nature Scientific Reports.

“Wild pigs can cause soil erosion, degrade water quality, destroy crops, and prey on small mammals, amphibians and birds.”

Wild boars were first brought to Canada from Europe in the late 1980s for livestock diversification. Their numbers quickly multiplied, making them the most prolific invasive mammal in Canada.

Wild pigs weigh between 120 and 250 pounds. They give birth to an average of six piglets per litter each year and can become sexually mature as young as 4 months old.

They can feed on all kinds of crops, as well as insects, birds, reptiles and small mammals, having a massive impact on the environment.

“They’ll root up the vegetation like a rototiller,” researcher Ruth Aschim told CBC News. “They’re rolling around in the water, defecating in it. There is crop damage, disease transmission, even automobile crashes with these pigs.”

In the U.S., northern states are keeping an eye on the feral pigs, hoping none make their way across the border. Wild pigs already exist in about 30 states, according to the National Post, but these are Southern states and the wild pigs are mostly descendants of domesticated pigs that escaped.

“We know the damage that they’ve done in other states, south of us in particular … the state has taken a really strong stance to try to prevent the establishment of any feral swine,” said John Steuber, state director of Wildlife Services in Montana. “We don’t want any more invasive species in the state.”