They aren't quite flying, but feral pigs are crossing major roads and even swimming through rivers as they invade Sydney's suburbs.
Authorities say the diseased and destructive animals have gone as far as Pymble and Hurstville while wreaking havoc on the rural fringes.
Hundreds of feral pigs are found and killed in Sydney each year by the Greater Sydney Local Land Services, which considers them a major biosecurity threat because they carry diseases such as leptospirosis and Q fever.
Biosecurity manager Steve Parker said the pigs would stop at nothing to get a meal.
''We have known pigs to swim quite significant rivers to get from where they are harbouring to areas where they're feeding,'' he said. ''We've had pigs cross fairly major road networks as well.''
Mr Parker said the feral pigs can weigh up to 100 kilograms and will destroy forests, farms and gardens as they dig and scavenge for food. He has known them to cause $20,000 worth of damage to a single farm crop.
The native and once common long-nosed bandicoot has been almost entirely pushed out of Sydney by pigs and other introduced pests such as foxes and cats.
Authorities do not know the number of feral pigs in Sydney but they do know how they got here; some populations have been living on the city's bushland fringes for generations, but every year more are dumped by hunters who have relocated them from rural NSW.
''Often those pigs are released when people can't care and cater for them,'' Mr Parker said.
His team destroys 50 to 60 pigs in Sydney each year that have either been released, escaped or found in someone's backyard.
''We've turned up to front yards completely dug up, looking like someone had been through and ploughed a paddock,'' he said.
Maximum penalties under the Local Land Services Act 2013 range from $2000 for keeping feral pigs in captivity to $5500 for releasing them and $22,000 for transporting them.
Three men pleaded guilty in Campbelltown court after police found one dead and two live pigs in their ute in Bathurst last year.
Sydney's wild roaming feral pigs are baited, trapped or shot. Biosecurity officers say pigs that have spent time in captivity have negative associations with traps and are reluctant to enter them, making poisoned bait more effective.
One feral pig mob in Penrith that Mr Parker has monitored on hidden surveillance cameras is being poisoned with 1080 pesticide.
He is reluctant to advertise the whereabouts of the baiting because he has known it to attract pig hunters too. He says the hunters steal the cameras and, in the case of traps, he has known them to release caught pigs only to hunt them down with dogs later.
The story Feral pigs' appetite for mayhem turns properties into sties first appeared on The Sydney Morning Herald.