A ratter is a dog or cat bred and trained specifically to hunt and kill rats. Throughout history, rats have been serious pests in homes, farms, barns, and ships, eating stored grain, spreading disease, and damaging property. Ratters became valuable working animals, prized for their speed, determination, and natural hunting instinct.

Some dog breeds became famous as ratters: terriers like the Jack Russell or Rat Terrier got their names from this very job. These dogs were small enough to chase rats into tight spaces but fearless and quick enough to catch them. In Victorian England, rat-catching competitions drew huge crowds who watched ratters kill many rats in minutes.

Cats served as ratters too, especially on ships and in warehouses. A good ship's cat could keep an entire vessel free of rats during long ocean voyages. Farmers relied on barn cats as ratters to protect their grain supplies.

While pest control is mostly handled by professionals today, some farms and rural properties still keep ratters, and certain dog breeds maintain their strong rat-hunting instincts even when they live as family pets.