Japan Beaches on High Alert for Unusual Dolphin Attacks; Single Aggressive Dolphin Suspected

At certain beaches in Japan, extensive security measures are being implemented not to guard against sharks, but rather a lone, sexually frustrated dolphin. According to the BBC, this particular dolphin has been linked to a troubling surge in attacks on swimmers in Wakasa Bay, located approximately 300 kilometers from Tokyo. So far in 2024, there have been 18 reported attacks, including one involving a primary school child who required 20 stitches for injuries to their fingers.

Frequency of attacks

The frequency of these attacks has noticeably increased, with just one incident reported in 2022, six in 2023, and the current year’s tally already at 18. Local authorities are convinced that a single dolphin is responsible for these aggressive encounters.

“It is reasonable to assume that it is the same individual, as the wounds on the tail fin are similar to those of the dolphins seen off the coast last year, and it is rare for dolphins, which normally move in groups, to be alone for such a long time,” explained Tadamichi Morisaka, a cetology professor at Japan’s Mie University, in an interview with Japanese outlet NHK. Each dolphin’s dorsal fin, akin to a human fingerprint, features unique notches, ridges, and pigmentation that can help identify individuals.

Experts speculation

Experts have speculated on the reasons behind the dolphin’s unusual behavior. “Bottlenose dolphins are highly social animals, and this sociality can be expressed in very physical ways. Just as in humans and other social animals, hormonal fluctuations, sexual frustration, or the desire to dominate might drive the dolphin to injure the people it interacts with. Since they are such powerful animals, this can lead to serious injury in humans,” noted Dr. Simon Allen, a biologist and principal investigator with the Shark Bay Dolphin Research Project, in a conversation with the BBC.

Dr. Allen suggested that the dolphin could have been excluded from its community and might be seeking companionship, which could explain its aggressive behavior.

Dr. Matthias Hoffmann-Kuhnt, a marine mammal expert at the National University of Singapore, added, “Most of the time, in my experience, this is more a defensive behavior when humans get too close to these dolphins and do not know how to conduct themselves.”

Despite dolphins being generally friendly towards humans, their attacks can indeed be dangerous. A notorious case from Brazil in 1994 saw a dolphin nicknamed Tiao injure 22 people, highlighting the potential severity of such encounters.

In response to the recent incidents, authorities in the coastal town of Mihama have placed warning signs for beachgoers. The signs caution that the dolphins not only have sharp teeth capable of causing serious injuries but also have the strength to drag individuals into deeper waters, posing a life-threatening risk.