An endangered dolphin whose blowhole was deformed or became injured has learned to breathe through its mouth.
Biologists studying a pod of Hector's dolphins off the coast of New Zealand were surprised to see the adult dolphin surfacing in an unusual way compared to other members of its group.
Rather than breathing out of its blowhole like the rest of its species, the creature emerged from the water at a steep angle with its head higher than normal.
This allowed it to take gulps of air as it broke the surface of the water before diving beneath the waves again.
It is one of the only known examples of a dolphin learning to breathe through its mouth.
Writing in the journal Marine Mammal Science, Professor Stephen Dawson, a marine biologist at the University of Otago in New Zealand, and his colleagues said: 'In every surfacing we observed, the dolphin approached the surface at a steep angle, with its head emerging higher than normal from the water surface.
"The blowhole did not open widely as is normal.
"While the blowhole appeared closed throughout each surfacing event, in surfacings seen at close range, a small puff of spray was visible from both blowhole and mouth as these cleared the surface at the beginning of the surfacing sequence."
The researchers believe the dolphin may have suffered an injury that stopped it from opening its blowhole properly or suffered from some sort of developmental problem.
The only damage they could see to the animal's blowhole was a small lesion on one side.
While researchers found a small lesion next to the mouth-breathing dolphin's blowhole, they are unclear about what exactly caused it not to work properly.
It could have suffered an injury to the vital air cavity, which is equivalent to our nose, or perhaps had a developmental defect.
The dolphin could also have suffered a blockage in its blowhole.
Two pilot whales discovered on the Dutch coastline were found to have died after their blowholes became blocked by flatfish.
Common sole appear to have swam into the marine mammal's nasal cavity and become stuck there after the whales swallowed them while feeding.
The whales then essentially choked to death.