Okunoshima was Japan's secret location for producing poison gas between 1929 and 1945. It is often called Usagi Jima, or Rabbit Island, because of the hundreds of feral rabbits that roam the island. Rabbits were used to test the poison gas as it was being developed. According to popular legend, the rabbits were set loose after production ceased, accounting for the current wild rabbit population. The island has a small museum and the remains of the gas production facilities. Visitors may tour the remains to learn of the island's past, while the rabbits compete for attention. The rabbits' diet consists mainly of food brought to the island by visitors, fresh vegetables and commercial rabbit feed.