And when they happen in public places, and people have camera phones, rats go viral. They scurry through social media. They're the Kardashians of pests.
A video of rats picnicking around pizza boxes at the popular 13th and Locust Green Eggs Café last Sunday exploded on Twitter and blogs. The video aired on local newscasts, repeatedly. It became the talk of the town, Internet, radio shows. Many comments were as nasty as the subject.
Chances are you had a better week than Stephen Slaughter. Said the managing partner of the Green Eggs Cafés, "This is not something I ever want to relive again."
His newest location, which opened in April 2012, closed immediately. Business dropped by half at his cafés in South Philly and Northern Liberties. This is the damage rodents, abetted by video, can do.
"Wherever there are people, specifically people's food, there are rats," explained Raymond Delaney, who manages the city Public Health Department's Vector Control program. Delaney kindly met me with three of his colleagues at the city's top site for rats.
Yes, the city's toniest village green, its sumptuous lounge, and home to elegant multimillion-dollar homes. And rats.
Vector Control comes to the square two or three times a week year-round, in part because the park's popularity rarely wanes.
"It's the people feeding themselves and the animals," Delaney said. "When they feed the squirrels, they're also feeding the rats."
His advice: Don't feed either.
In the southwest corner near the bronze billy goat statue, Lawrence Credle shoved half a cup of rat-poison pellets through PVC pipe deep into eight burrows while we spoke. The shadow of a brown Norway rat - that's our national rat - bustled behind the garden shed's ivy.
Rats are not known for their discriminating palates. They eat high and low, T-bones, cold pizza, and, well, matters best not discussed at the breakfast table or elsewhere. Put it this way: They are nature's true omnivores, and, if you didn't think they were disgusting enough, cannibals.
However, they no longer spread the plague. In the early 20th century, the city Department of Health and Charities accepted 5 cents for live vermin, 2 cents for dead at the Rat Receiving Station at the Race Street Pier. Today, the concern is salmonella - "the sewers are their highways," Delaney said - and rat-bite fever. "We get calls about five or six rat bites a year," said supervisor Rosalie Neris who, as a teenager, kept a pet rat.
Rats procreate all year long, gestate in less than a month, as many as six times a year, with litters of six to 10 pups. They live a year. They have been videoed on the White House lawn. New York City subways are so overrun - poison failed – that the Metropolitan Transit Authority is now trying sterilization.
During the last two years, Philadelphia's rat population has remained fairly constant. Or rather the complaints have been, almost 800 for May. Sightings peak in the summer, when more people - and food - are outside.
Vector Control responds only to residential and public properties. A different health division, Food Protection, inspects restaurants. Rats and mosquitoes, breeders of disease, are the program's priorities, though they will remove low-hanging wasp nests on city trees. The program doesn't do mice, raccoons, deer, or skunks.
Camera phones will not make Vector Control's life any easier. The staff learned about the café's problems the same way everyone else did.
Then again, so did the café owners.
Rats were here long before humans and, Delaney said, "I don't think we'll ever control them."
The website Foobooz, which treated the rat video as its Watergate, ran a poll as to whether diners would patronize Green Eggs again. As of Friday afternoon, more than 1,000 readers had responded, with 44 percent saying yes.
Last week, Green Eggs had an exterminator fix a damaged sewage drain pipe and a hole in the building. The owners have applied for a permit to dig up pipes and pour a thick concrete wall to seal the building's basement perimeter.
"We want to make it extremely clear that this was an isolated incident," the restaurant will announce on its Facebook page this week, "and that Green Eggs Café maintains an extremely clean service environment and our health records will prove that to anyone who looks. To those who have supported us unwaveringly: we thank you, you are what makes this city great and we hope to be back as soon as possible!"
With any luck, Slaughter told me, by Memorial Day.