Dolphins terrorize and bite beachgoers in Japan — for the 2nd year in a row

Dolphins attacked four people swimming in the sea off the coast of Japan on Sunday (July 16), leaving one man in his 60s with several broken ribs.

This is the second year in a row that dolphins have injured humans at beaches in Fukui prefecture, on the Sea of Japan coast. Last summer, at least six people were bitten by a single animal — thought to be an Indo-Pacific bottlenose dolphin (Tursiops aduncus) — with the most serious case requiring 14 stitches to close a gash at the base of the victim's thumb, according to the Japanese news site The Mainichi.

Both this year and last, dolphins came right up to the edge of the water. The man whose ribs splintered had been swimming 16 feet (5 meters) from the shore at Suishohama Beach when a dolphin rammed and bit him, local police told the Asahi Shimbun news site in Japan. Another man sustained bites on his left arm the same morning, and the BBC reported that two more beachgoers were attacked later that day, although there are few details about these incidents.

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A dolphin was also filmed seemingly terrorizing people at the same beach on Monday (July 17). A video of the attack posted by BreakingOne shows people hastily exiting the water at the sight of a dolphin that is cruising in the shallows and making a beeline for a woman in a pink rubber ring. 

It then appears to nip the woman's legs, rocking the inflatable. After a few seconds, the dolphin swims away from the beach and toward two people in a dinghy towing a third person in a rubber ring.

The recent incidents bring the number of reported dolphin attacks in Fukui to six this year, police said, but it remains unclear if they were all perpetrated by the same animal. Authorities have warned swimmers against approaching or touching the mammals.

Wild dolphins rarely attack humans, with one reported case of a fatal attack in 1994, off the coast of São Paulo in Brazil. But the mammals have been known to bite or pull people underwater when they feel threatened, harassed or become habituated to being fed, according to National Oceanic and Atmospheric Administration (NOAA) Fisheries. If they have come to expect or rely on handouts, dolphins may become pushy and aggressive when they don't receive them, the agency says.

People should remember that dolphins are wild and extremely powerful animals, Giovanni Bearzi, a zoologist and president of the non-profit organization Dolphin Biology Conservation in Italy, told Live Science in an email. "A part of the problem may be that some humans tend to see them as pets, or as invariably 'nice' animals, sometimes overlooking the risks involved in dealing with wildlife," Bearzi said, adding that "our unaware or overly 'friendly' behavior may trigger aggression." 

Dolphins may also attack if they perceive that humans swimming in places important for their foraging or reproduction activities are ignoring the animals' warning signals, Bearzi said. "With human swimmers, the dolphins may send acoustic and other warnings that the swimmers fail to detect or interpret correctly. In other words, the dolphins may first tell the swimmers to 'go away,' and because the swimmers don't do that, an attack is triggered."

The attacks may have been triggered by a single dolphin with an especially aggressive personality, but they were probably cautionary, Bearzi said. "An adult bottlenose dolphin could easily kill a swimmer if [it] really intended to do so," he explained. "These attacks seem to be warnings rather than true attempts to do serious harm."