When The Health Inspector Is Away, The Cats Will . . .

But take away that cat and the subject of a well-worn axiom will take its place:

Across the city, delis and bodegas are a familiar and vital part of the streetscape, modest places where customers can pick up necessities, a container of milk, a can of soup, a loaf of bread.

Amid the goods found in the stores, there is one thing that many owners and employees say they cannot do without: their cats. And it goes beyond cuddly companionship. These cats are workers, tireless and enthusiastic hunters of unwanted vermin, and they typically do a far better job than exterminators and poisons.

When a bodega cat is on the prowl, workers say, rats and mice vanish.

. . .

But as efficient as the cats may be, their presence in stores can lead to legal trouble. The city’s health code and state law forbid animals in places where food or beverages are sold for human consumption. Fines range from $300 for a first offense to $2,000 or higher for subsequent offenses.

. . .

Still, many store owners keep cats despite the law, mainly because other options have failed and the fine for rodent feces is also $300. “It’s hard for bodega owners because they’re not supposed to have a cat, but they’re also not supposed to have rats,” said José Fernández, the president of the Bodega Association of the United States.

Luis Martinez, 42, has managed his brother’s grocery in East New York, Brooklyn, for two years. At first, despite weekly visits from an exterminator, the store’s inventory was ravaged constantly by nibbling vermin.

“Every night I had to put the bread in the freezer,” he said, pointing at shelves filled with bread and hamburger buns. “I was losing too much inventory. The chips and the Lipton soups all had holes in them.”

Then, last winter, a friend brought Mr. Martinez a marmalade kitten in need of a home. Mr. Martinez, who was skeptical of how one slinky kitten could fend off an army of hungry rats, set up a litter box in the back of the store, put down an old fleece jacket and named the kitten Junior.

Within two weeks, Mr. Martinez said, “a miracle.”

“Before you’d see giant rats running in off the streets into the store, but since Junior, no more,” he said.