The world’s first known case of porpoise conjoined twins have been caught in waters off the coast of the Netherlands.
The phenomenon, which has left the creature with a single body and two fully-grown heads, is known as ‘partial twinning’. The porpoise was captured by a fisherman on May 30.
Conjoined twin mammals are extremely rare. This is only the 10th known case of twinning cetaceans – a group including whales, dolphins and porpoises – known worldwide, according to a paper detailing the discovery published in the Online Journal of the Natural History Museum Rotterdam.
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“Even normal twinning is extremely rare in cetaceans,” wrote researchers, citing that only 0.5 per cent of all known pregnant cetaceans are estimated to have a carried a twin pregnancy.
“There is simply not enough room in the body of the female to give room to more than one fetus,” Dr Erwin Kompanje told New Scientist.
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Fishermen captured the animal inadvertently and, fearing it was illegal to bring it to shore, threw it back into the sea after taking a series of photographs.
While they don’t have the porpoise’s body to inspect, researchers are satisfied the discovery will fill a huge gap in the understanding of conjoined cetaceans, and partial twinning harbour porpoises in particular.