There was a cat named Tibbles who was owned by a lighthouse keeper. The cat became infamous as the only animal to have wiped out an entire species by itself. The bird species in question was the Stephens Island wren. Because there were originally no predators in that part of the world where it evolved, the little bird lost the ability to fly. When South Pacific islanders arrived, they brought rats on their ships. The rats quickly invaded the island. The wrens, completely helpless against the sudden attack of the ruthless predator, were quickly exterminated. Their last rat‑free refuge was Stephens Island, a one‑square‑miletiny spit of rock off New Zealand's coast.
When a lighthouse was established there, its keeper brought along his cat, Tibbles. Tibbles got straight to work, attacking the little wrens wherever he found them, hauling them by a dozen back to the lighthouse. Lyall kept several, which found their way to ornithologists. In 1895 the little animal was given the Latin name Xenicus lyalli and soon afterward it was declared extinct. The ecological destruction started by a pack of rats was completed by a lone cat. It never occurred to the lighthouse keeper, or anyone else, that given the uniquely fragile nature of the Stephens Island animal world, it might have been a good idea to keeo Tibbles indoors. (From: 100 Cats Who Changed Civilization by Sam Stall).