Dolphin attacks leave 4 swimmers injured

While many people believe that dolphins are "harmless and playful", recent dolphin attacks off Suishohama beach in central Japan may prove them wrong.

Four swimmers were injured on Sunday by dolphin attacks on the popular beach, officials said Monday.

First, a dolphin broke the ribs of a 60-year-old man, leaving bites on his hands after the sea creature rammed him on early on Sunday.

Then, in a separate incident the same morning, a 40-year-old man sustained bites on his arm.

Two other attacks by the mammals on the same day brought the count of such attacks this year up to six, local police said, adding that warning signs advising people to avoid dolphins have been put up.

Two women in Ieland were injured in ten days by the same dolphin in 2013. One of them suffered from a broken rib. A year later, a dolphin aggressively encircled five swimmers, who had to be rescued.

According to scientists, a plausible explanation for why the otherwise playful and purportedly "harmless" mammal may turn aggressive is that wild bottlenose dolphins find it "incredibly stressful" to swim alongside humans, as this may affect their behaviour patterns.

However, while their hostility to humans may still surprise some, dolphins have been known to be aggressive toward other sea creatures.

Recently, a video went viral, showing a bottlenose dolphin flipping a porpoise into the air off the coast of England.