November 14, 2025
TOKYO – A team of researchers led by a professor at Fukushima University is undertaking a rare initiative to resolve a question that arose during the process of producing a picture book.
The laboratory of Shingo Kaneko, 47, a professor at the Faculty of Symbiotic Systems Science at Fukushima University, is examining the lineage of rabbits inhabiting Okunoshima island in Takehara, Hiroshima Prefecture, which is known as “Rabbit Island.” Their research revealed a fact that could make people reflect on the relationship between humans and the environment.
The picture book, which is titled “Usagi no Shima” (Island of rabbits) and co-authored by Eri Kondo and Hiroshi Tateno, was published by Sekaibunkasha Inc. in June.
Set on Okunoshima island, home to hundreds of rabbits, it tells the story of the origins of one rabbit living on the island. Though the island is now famous as a tourist destination, it was once used to manufacture poison gas for the war, and rabbits were reportedly sacrificed as experimental animals.
The poison gas factory’s equipment was reportedly disposed of, and the rabbits were put down when Japan was defeated in the Pacific War. The rabbits inhabiting the island today are said to be descendants of ones released on the island in the 1970s.
The research began after one of the authors, Tateno, wondered whether the white rabbits on the island might carry genes from those used as experimental animals. He consulted Kaneko, a genetics specialist he had spoken to before, and the research tracing the rabbits’ origins began.
Shingo Kaneko, professor at Fukushima University, holds the picture book “Usagi no Shima” in his left hand. PHOTO: THE YOMIURI SHIMBUN
Fieldwork
The research team examined the DNA, or the genetic information, of the rabbits on the island to determine common family structures among them. For example, if all rabbits on the island were descendants from those released in the 1970s, all their DNA would be expected to share similar characteristics.
The professor and his lab students conducted fieldwork on the island in March last year. Since it is prohibited to touch rabbits on the island, they collected 264 droppings over three days, extracted DNA, and analyzed its characteristics.
Their research revealed that rabbits on the island possess DNA with diverse characteristics. “This indicates that reproduction occurred through the mixing of many groups, rather than a single group spreading its descendants,” the professor said. It shows that rabbits on the island formed families not only from the group of those initially released but also many others that were abandoned on the island one after another.
“We assumed that rabbits have been repeatedly abandoned on the island because there were many rabbits with different coat colors and other factors, but we had no scientific evidence until now,” said an official from the Environment Ministry’s Chugoku-Shikoku regional environment office, which oversees the island.
Leaving animals on the island may constitute an act that violates the animal welfare law. In addition, the number of rabbits has exceeded the level sustainable for their habitat because of humans feeding them.
“I hope [the study] will help people reflect on the significant impact humans have on the environment,” Kaneko said.
“All I knew about this place was that it’s an island with rabbits, but now I understand it has a complex background,” said Koharu Naraoka, 22, a PhD candidate at the university who analyzed the data.
The picture book carries Kaneko’s explanations on the research at the end of it. “People rarely have the opportunity to see academic papers in their daily lives. I hope the picture book will help people become interested in the research,” he said. The group’s research findings will shortly be compiled into a paper.
In the picture book, one rabbit living on the island is portrayed as a symbolic presence that does not actually exist. Is there any possibility that descendants of rabbits that escaped culling after the war are living on the island?
“The possibility is low. However, since many lineages have been found to be intermingled, we cannot say it’s totally impossible,” Kaneko said.