Off the coast of Japan’s Ehime Prefecture lies Aoshima, a tiny former fishing community that became internationally famous as one of Japan’s best-known “Cat Islands.”

The cats were originally introduced for a practical reason. Fishermen kept them around boats and homes to control mice and rats, which could damage fishing equipment and food supplies.

But over the decades, the human and feline populations went in completely different directions.

As younger residents left Aoshima for opportunities on the Japanese mainland, the island’s human population gradually declined. Meanwhile, the cats continued reproducing, eventually becoming the overwhelming majority of the island’s inhabitants.

At various points, reports have estimated more than 100 cats compared with only a handful of permanent residents.

The island became an internet sensation, with photographs showing cats wandering through narrow paths, gathering around homes and lounging near the harbor. But there’s an important detail tourists sometimes miss: Aoshima isn’t a theme park or an official cat sanctuary. It is a real residential community where the remaining residents have to live alongside the animals.

The cat population has also been subject to spaying and neutering programs to prevent it from growing uncontrollably.

And although Aoshima is often described as having a 6-to-1 cat-to-human ratio, the exact numbers change as residents and animals come and go.

Still, the basic fact remains extraordinary.