We all have sometime or the other experienced first hand or watched on videos the friendly, playful and super smart behaviour of dolphins in controlled environments of water zoos or pools. But are they equally friendly or playful in their natural wild settings!
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Attacks on human on the beaches are not uncommon, but these are invariably attributed to sharks. Over the last three years, however, increasing attacks on humans on serene beaches in the Fukui prefecture in central Japan are being attributed by experts to rare aggressive behaviour by a ‘lonely’ single Indo-Pacific Bottlenose male dolphin.
According to Kyodo News quoting the Tsuruga Coast Guard Office, 18 people have been injured this summer at beaches in the prefecture as on August 27, including an elementary school student whose finger required 20 to 30 stitches and took a month to heal.
The number of incidents this year has increased rapidly compared to the last two, with at least one person injured in 2022 and five in 2023, according to the coast guard.
On August 27, a man in his 50s suffered bite injuries on both hands from a dolphin while he was swimming off Mizushima island in Tsuruga, marking the second consecutive day an incident occurred at the beach.
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Other victims in the past have even suffered broken bones after being rammed by the dolphin at some speed.
Kyodo News quoting Tadamichi Morisaka, a professor of cetology at Mie University, said that the dorsal fin characteristics of a dolphin spotted at the same beach a few days before the incident matched those of a 2.5-meter-long one observed off the coast of Fukui Prefecture up until last year.
“The dolphin may be coming to the beach in search of human interaction,” Morisaka said.
While dolphins in aquariums are often seen forming bonds with humans, frequent interaction with people can cause them to try to assert their dominance through behaviours like biting and ramming, Morisaki said, adding that in such situations people should “move away from the dolphin immediately.”
Ryoichi Matsubara, director of Echizen Matsushima Aquarium in Sakai, Fukui Prefecture, also warned that as some dolphins can be larger than bears, “contact with them can be very dangerous. It’s too late once a fatal accident occurs.”
The Kyodo News mentioned that capturing dolphins is generally prohibited under government regulations and Fukui prefectural officials have said they currently have no plans to do so in this instance.
Some beaches have begun installing devices that emit ultrasonic waves as a deterrent (how effective they prove is yet to be ascertained) while swimmers are warned to leave the water immediately if they encounter a dolphin.
Discussing common dolphin behaviours that could explain such aggressive encounters with people, an article in Nature, quotes Dolphin ecologist Tadamichi Morisaka as saying Bottlenose dolphins typically live in pods. The males form lifelong partnerships with other males. Hanging out in pairs gives them better access to females, because two is stronger than one.
These pairs spend hours and hours being playful with each other. This includes behaviours like chasing each other and rubbing the other dolphin with their pectoral fins – which is thought to signal fondness – and even sexual behaviours, such as pressing their penises against each other. Gentle biting is one of these pro-social behaviours.
So, the dolphin in Fukui has probably isolated itself from its pod or pair mate, which is not an uncommon behaviour, and is looking for a relationship acting like he’s playing with a male pair mate. In the process, humans are suffering injuries with gentle bites (by dolphin standards), according to the expert.
