Okunoshima, a small island in Japan’s Inland Sea known for its large population of tame rabbits, continues to face significant ecological challenges amid growing tourism. Located within Hiroshima Prefecture, the 70-hectare island attracted approximately 195,000 visitors in 2024, many of whom bring food such as carrots and cabbages for the rabbits. While this has contributed to a booming rabbit population, it has also led to considerable environmental damage.
A recent study led by a team of 12 Japanese scientists, published in the Journal of Ecotourism, highlights that the number of rabbits significantly exceeds the island’s natural carrying capacity. Their feeding habits have caused extensive loss of vegetation, including the disappearance of leaves and branches up to a visible "rabbit line" around the island. This phenomenon is comparable to the "deer line" previously observed in areas affected by overabundant sika deer populations.
The research also documents unusual predation behavior by wild boars on Okunoshima. On March 5, 2024, a wild boar was observed attacking and killing a rabbit, marking a rare instance of active predation rather than scavenging. Professor Shin-go Kaneko of Fukushima University, lead author of the study, noted that wild boars typically scavenge carcasses and are not commonly predators of live animals. However, boars have been seen frequenting the island's jetty, drawn by leftover rabbit food discarded by visitors.
This congregation of wild boars near human activity has raised concerns about potential risks to public safety. Last month, a wild boar in the city of Toyota attacked and injured four men in an incident that gained widespread attention on social media. Kaneko suggested that human-provided food may be encouraging the boars to settle in these areas, potentially altering their natural behavior and increasing the risk of human-wildlife conflict. He has recommended culling measures as a possible response to mitigate these impacts and protect the island’s ecosystem.
Okunoshima’s rabbits also have a complex and dark historical background. The island served as a production site for chemical weapons during World War II, where agents like mustard gas, phosgene, and cyanide were manufactured for use by the Japanese Imperial Army. Local stories suggest that the current rabbit population might descend from laboratory animals used during this period. However, genetic analysis of rabbit droppings conducted by Kaneko’s team indicates a more diverse origin, likely including domestic rabbits released by visitors after the island became a popular tourist destination.
In addition to natural predators, rabbits on the island have faced harm from human actions. In a notable incident last year, Ryu Tota, aged 25, received a suspended sentence after being found guilty of killing a rabbit and harming others. Over a three-month period, authorities discovered 77 deceased rabbits on Okunoshima, though the exact causes of death in many cases remain unclear.
The situation on Okunoshima illustrates the complex challenges of balancing tourism, wildlife management, and ecological preservation on a unique yet fragile island ecosystem.