Experts also believe the dolphin may be sexually frustrated following reports in other incidents that it attempted to press its genitals against its victims.
“Bottlenose dolphins are highly social animals and this sociality can be expressed in very physical ways,” Dr Simon Allen, a biologist and principal investigator with the Shark Bay Dolphin Research project, told the BBC.
“Just as in humans and other social animals, hormonal fluctuations, sexual frustration or the desire to dominate might drive the dolphin to injuring the people it interacts with. Since they are such powerful animals, this can lead to serious injury in humans.”
Dr Allen added that the dolphin may have been shunned from his own community and could therefore be seeking “alternative companionship”.
Shoichi Takeuchi, of the Tsuruga Coast Guard office, said emergency medical teams had been summoned to treat people who had been attacked over the summer, with those who had sustained minor cuts and abrasions allowed to go home, but others requiring their wounds to be disinfected and stitched.
The authorities have since posted signs warning swimmers of the dangers, including a picture of a dolphin baring its teeth.
“If people see a dolphin off the beach, we advise them to get out of the water immediately, to keep their distance and not try to feed them,” Mr Takeuchi said.
Mr Goto says he is not taking any chances. “Whenever I look at the sea, I can’t help but think a dolphin might be out there. I’ll never go back.”
