A wild dolphin rams a swimmer and bites him at a beach in Mihama, Fukui Prefecture, on Aug. 14. (Provided by a swimmer)

Photo/Illutration A wild dolphin swims around people at a beach in Echizen, Fukui Prefecture, in 2022. A man was bitten shortly before the photograph was taken. (Provided by a swimmer)

FUKUI--Suspicions have emerged that a rogue dolphin may be responsible for a spate of attacks off Fukui Prefecture over the past three years that left at least 53 people with wounds and sometimes broken bones.

Most of the victims attacked by dolphins were bitten on their arms and hands, and seven were rammed by the mammals.

Twenty people were injured between July 21 and Aug. 20 this year, after 12 victims in 2023 and 21 in 2022, according to records The Asahi Shimbun obtained from prefectural police and the Tsuruga Coast Guard Office.

More people are believed to have been injured because some victims did not report the matter to authorities or went to hospital on their own, sources said.

Dolphins have repeatedly appeared along local beaches crowded with bathers.

Fifty of the victims were at beaches designated for swimming. Among the remaining three, two were at rocky patches near beaches and one was offshore.

Swimming beaches in Fukui Prefecture attract visitors from inside and outside the prefecture.

Most of the victims were out-of-towners. Eleven were from Aichi Prefecture, followed by eight from Gifu, five from Kyoto and four from Mie.

In each incident, only one dolphin was present. There are no records of two or more dolphins appearing at the same time.

Images of a lone dolphin caught by camera along the coasts of Fukui and Ishikawa prefectures all share a single trait: a mammal with an injured dorsal fin.

Tadamichi Morisaka, a professor of cetology at Mie University, visited sites where some of the attacks occurred.

He suspects a single Indo-Pacific bottlenose dolphin that has become used to bathers is responsible for all the incidents.

Morisaka was not aware of reports elsewhere in the world about so many people being intermittently injured by wild dolphins.

Indo-Pacific bottlenose dolphins live in schools. Morisaka believes that the individual in question is a solitary dolphin roaming along the coast of Fukui Prefecture.

Many of the victims were bitten after they stroked a dolphin or tried to shake off a mammal that snuggled up to them, according to records from the prefectural police and the coast guard.

A 66-year-old man was bitten on his left hand when he grabbed the dorsal fin of a dolphin in shallow waters in Tsuruga, Fukui Prefecture, on Aug. 4. The injury took 10 days to heal.

Dolphins have the habit of rubbing their bodies against each other and lightly biting to interact with peers.

Ryoichi Matsubara, director of the Echizen Matsushima Aquarium in Sakai, Fukui Prefecture, said, “Even if dolphins gently bite, if people reflexively withdraw their hands, they can get seriously injured.”

He warned people against approaching or touching dolphins.

Seven cases involved a dolphin ramming a victim.

A 33-year-old man playing with a dolphin in Mihama, Fukui Prefecture, on June 20, 2023, got the shock of his life when his foot hit its head. The dolphin’s behavior changed immediately, and it repeatedly dashed itself against him.

Experts say the most severe type of ramming is a rush, which can prove fatal. The British Broadcasting Corp. reported such a case in Brazil in 1994.

Experts were puzzled by the gender disparity in the Japan attacks because an overwhelming majority, or 43 victims, were men. Women accounted for nine. The gender of one victim is unknown.