Two-headed Conjoined Porpoises Hauled Up from the Deep

By Tia Ghose, Senior Writer | June 15, 2017 07:39am ET 

Two-headed conjoined porpoises were recently hauled up by a fishing boat in the North Sea, not far off the coast of the Netherlands.

The bizarre-looking creatures were already dead, and the fishermen, who feared trouble from the authorities, took photos and then tossed the duo back overboard.

It's not clear exactly why the porpoises died, but the double-headed creatures likely could not swim, said Erwin Kompanje, a researcher at the Natural History Museum and the Erasmus MC University Medical Center in Rotterdam, the Netherlands, who recently wrote up the case in the June 7 issue of the journal Deinsea. Another cause may have been their fused hearts, which may not have worked adequately, Kompanje said. 

Conjoined twins

Conjoined twins are a rarity for humans, but they're also extremely rare for harbor porpoises (Phocoena phocoena), Kompanje said. That's because newborn dolphins and porpoises, which are mammals, need to immediately start swimming on their own or they drown, Kompanje said.

"Normal twins are extremely rare in cetaceans, as there is not enough room in the mother's body to have more than one fetus," Kompanje told Live Science. One case report pegged the incidence of twinning in cetaceans at less than 1 in 200.

Only one past case of a harbor porpoise bearing twins has ever been reported. Given the rarity of twinning, it stands to reason that conjoined twins are even more of an oddity, he added. In the past, only nine other cases of conjoined twins have been reported in whales or dolphins, and most of these were described in fetuses pulled from dead pregnant females, according to the study.

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