Urban rat populations are booming across the world and the Australian city is no exception. Is the solution pesticide, conceding defeat - or more rats?
Nathaly Haeren has seen patios in Sydney collapse because brown rats have tunnelled under and created sinkholes. She's been electrocuted in the roof of a house after they chewed through air conditioning wiring. She's even visited a hairdresser where they'd gnawed a circle through double brick.
More recently, Haeren has started seeing rats standing in the street in the middle of the day, "oblivious" and unbothered - like they just don't care.
"It's the destruction they cause that blows my mind, that scares me, because I'm competing against them," the owner of Pesty Girls pest management says.
"Rats need to keep gnawing to keep their teeth down. Their strength is like iron. And they can flatten to the size of your thumb - they've got hinged ribs ... I need to be 10 steps ahead."
Haeren says rats have become a problem "all across Sydney". And her requests have spiked to record levels since the pandemic.
Anecdotally, numbers are high. A string of viral videos showing rat incursions into typically human spaces in recent months has instilled terror into the hearts of some Sydneysiders. In December, rodents made headlines when "giant rats" were filmed "brazenly" scurrying around the Westfield food court in Parramatta. A month later, at least half a dozen rats were filmed running wild in the kitchen of a late-night kebab shop on Oxford Street, deterring some from the business.
But nobody really knows how many rats live in Sydney. There's no rat census and given that a rat's pregnancy lasts just three weeks and can produce a litter of more than a dozen pups, any population count is at risk of becoming quickly outdated.
Haeren attributes their visible spread across the city to construction pushing them above ground and changing bin cycles allowing residential waste to sit for longer periods. New research suggests invasive rats are becoming increasingly resistant to poisons, posing challenges for councils and pest controllers.
The study's author, Edith Cowan University PhD candidate Alicia Gorbould, says the finding should be a warning sign.
"Australia has been using these poisons for more than 50 years in an unchecked way, with few restrictions," she says. "Many countries are putting restrictions on regular pesticides, but if we continue as we are, we can also feed into that cycle of resistance.
"We need a more coordinated approach to rodent management, and that's not happening."
In 2019, the city of Sydney reported an increase in the vermin population that the council said had been encouraged by "unprecedented" levels of construction. Sydney's first outbreak of leptospirosis, which is spread through rodent urine and killed seven dogs, was linked to the 2019 explosion in the rat population. The disease can also be fatal in humans.
Rats have been associated with dozens of human diseases and parasites around the world, including indirectly spreading Lyme disease, plagues and typhus through fleas. Over the past 10 centuries, rat-borne diseases may have taken more lives than all of the wars ever fought.
Since the 2019 outbreak, leptospirosis has popped up in urban areas around Sydney, the Australian Small Animal Veterinarians president, Julia Crawford, says.
She and the founder of Southern Cross Vet, Sam Kovac, argue more research and surveillance are needed in order to prevent further outbreaks of the disease and deaths of beloved dogs.
The harm rats can pose goes beyond our family pets.
A city of Sydney spokesperson says the greatest health and safety risks posed by rats are disease transmission, food contamination via their droppings, urine and hair, and structural damage. The spokesperson says recent sightings and complaints also suggest rodents are a "key concern" for residents in social housing estates, who shared communal bin rooms.
The council spends about $240,000 a year on pest control. Alongside rat baits, it operates a "risk-based rodent control program" on streets and at parks, manned by more than 100 staff and contractors with the assistance of 40 electronic multi-catch units in locations where rodent activity is high.
The baits are rotated on a quarterly basis to prevent rats becoming resistant to their active ingredients. During severe infestations, licensed pest control contractors also carry out targeted burrow baiting.
Across the state, councils and private operators are responding to concerns about increased rat populations with a mixture of methods.
Shaun Bankowski has operated his pest control business, MOA Contract Shooting, throughout New South Wales since 2015. He says he has never been in higher demand to deal with rat outbreaks - from shopping centres to food manufacturing sites, chicken farms and warehouses.
"We've had sites where we've shot over 650 rats in four hours," he says. "The whole back of my HiLux was covered in rats - 15cm deep."
Most services use the integrated pest management method, which first eliminates the reasons why rats are drawn to the site, like clutter and food sources, then lays down traps and baits. But Bankowski says that's no longer sufficient.
"Say you've got 100 rats - 80% of them will die from the poison and the traps, but then you'll have that 20% that are immune," he says. "They breed up and then you've got a colony that's immune to poisons.
"I come in, get rid of as much as you can with a shoot and then drop poison on them. That usually knocks them out."
If it sounds grisly, he says, the rats die as humanely as possible.
"I can hit a 50c piece at about 120 metres," he says. "We always make sure that we got a clean shot, in the head or in the chest."
Urban rat numbers around the world are increasing due to climate change, urbanisation and growing human populations, forcing cities to grapple with whether to continue to fight the war on rats or concede defeat.
In New York, the city's first "rat tsar" was hired by the mayor in 2023, following a competitive application process that called for "bloodthirsty" applicants who possessed "killer instincts".
Not all cities have approached the issue with such murderous intent. In Paris, where there are estimated to be more rodents than people, the city authorities have transitioned from battling rats to investigating ways to peacefully coexist with them.
"No one should aim to exterminate Paris's rats and they're useful in maintaining the sewers,"deputy mayor Anne-Claire Boux said in the lead-up to the 2024 Paris Olympics.
"The point is that they should stay in the sewers."
Research published in Urban Ecology in 2022 found rat management may be a "wicked problem for which there is no overarching solution". Rather than engaging in a "war on rats", it said the focus should instead be on "improving the overall health of the community, instead of on eliminating rats".
The study found in all major rat interventions, populations had either remained at consistent levels, or reduced dramatically and then bounced back.
It also noted that they didn't just spread illnesses, but something more existential. The presence of rats, the report said, added "anxiety and fear into the tapestry of issues that people face daily".
The black rat (Rattus rattus) and the brown or Norway rat (Rattus norvegicus) arrived in Australia with the First Fleet in the late 1700s and their numbers quickly exploded, taking to Australia's shores so naturally that some settlers thought they'd always been here.
But while the invasive species would spread disease, damage buildings and agriculture, pillage bird nests and disrupt the environment, more than 60 native species of rat had already lived in Australia for up to 4m years, causing little to no harm at all.
The most common native species in cities is the bush rat, a shy rodent that was the unintended victim of a campaign to exterminate black rats during a plague epidemic in the early 1900s that killed about 500 people in Australia, mostly in Sydney.
Peter Banks, a conservation biology professor at the University of Sydney, says native rats could now be Australia’s secret weapon against invasive species.
He’s among academics that have been running programs to reintroduce bush rats to areas around the Sydney harbour they once inhabited, to block reinvasion by black rats.
Bush rats may look similar to invasive species but they don’t cause disease. They don’t smell. They live largely separate lives to humans, hidden in burrows during the day and opting for a diet of seeds, fruit and nectar instead of our trash.
"Once we removed [black rats], the bush rats would fill the area, and really dramatically reduce the black rat population," Banks says.
"They're quite symmetrical competitors - but the black rat really doesn't like a fight. They occupy the empty spaces in the natural world and if there's something there to give them a hard time, they don't thrive.
"They're really used to living off us, so by restoring the bush, we can make it unfriendly for [invasive] rats."
However, he says, “there’s an argument to be had that the urban environment is their natural environment. We think about them as pests, and they can be pests for us, but we don’t go trying to wipe out other species in their natural habitats.”
For now, at least, the rats are home too - and they’re here to stay.