The United States' wild pig population is soaring and rapidly multiplying, with experts describing it as a ticking "feral swine bomb", according to a new report.
There are roughly nine million feral hogs in the US. And those numbers are ballooning.
Each year the pigs cause an estimated US$2.5 billion in damage and control costs, according to the US Department of Agriculture (USDA).
Out-of-control pig populations means the damage will only get worse, experts said.
Dale Nolte, manager of the National Feral Swine Damage Management Programme at the USDA told The Atlantic that the increasing numbers of feral hogs in the US is referred to as a "ferral swine bomb".
Nolte said because they can reproduce so quickly, it's difficult to control the problem.
"I've heard it referred to as a feral swine bomb," Nolte said. "They multiply so rapidly. To go from a thousand to two thousand, it's not a big deal. But if you've got a million, it doesn't take long to get to four [million], then eight million."
University of Saskatchewan biologist who researches wild pigs, Ryan Brook, said that most of the swine are a mixture of domestic breeds and European wild boar.
"The problem with the hybrids is you get all of the massive benefits of all of that genetics," Brook told The Atlantic. "It creates what we'd call super-pigs."
Brook said wild hybrid "super-pigs" are intelligent and have a very good sense of smell.
They also have heavy fur, increasing their ability to survive in the wild.
The hybrids also gain benefits from domestic pigs - which are bred to be fertile year-round and to have large litters — an average of 10 piglets in each.
The feral swine cause damage to property, crops, livestock, native species and ecosystems and cultural and historic resources, the USDA's website said. They also threaten the health of "people, wildlife, pets and other domestic animals".
The US is not alone with its pig problem.
Last week in Hong Kong a video of wild boars swimming in the Bank of China Tower's pool in the heart of the city went viral. The swine family had visited Hong Kong Park earlier in the day.
The animals were returned to the wooded hillside area shortly after the arrival of staff from Hong Kong's Agriculture, Fisheries and Conservation Department (AFCD).
Wild boars have increasingly been seen venturing out of the woods and into Hong Kong's urban areas in recent years.
But not all encounters with the rogue animals are peaceful.
In October 2018, two elderly Hongkongers were sent to hospital after being rammed and bitten by a boar at a public housing estate in Diamond Hill.
In July the same year, a 39-year-old woman was attacked by a boar near an exit of the MTR's HKU station, while another woman reported that her husband had been injured by a wild pig on nearby Babington Path.
The University of Hong Kong issued a warning to staff and students to be on the lookout for boars.
As of March last year, 166 wild pigs were captured, and 121 of them were relocated to remote countryside areas around Hong Kong.
In the 2019-20 financial year, the AFCD also upped the number of staff members responsible for managing the city's wild pigs from six to 26.
- additional reporting South China Morning Post