© Simon AllenGone fishing ... a dolphin with a sponge on its head for foraging.
They use their long snouts to lift heavy conch shells to the surface and then shake them about in the hunt for fish that have sought refuge inside.
Simon Allen, a marine biologist at Murdoch University, said dolphins in Shark Bay are renowned for their "remarkable array" of sophisticated behaviours, including using sponges as tools and beaching themselves intentionally in pursuit of fish in shallow waters.
But he and his colleagues were shocked when they first saw a dolphin suddenly appear with a massive conch on its head (image below).
"We nearly fell off the boat. It looked like a unicorn," he said. "It was a fantastic wildlife encounter."
They thought the dolphin might have been using the shell as a toy or been showing off to its fellow cetaceans.
© Kathrin Bacher, University of ZurichA dolphin eats fish from a conch shell.
"The photographs indicate the dolphin lifted the conch out of the water and manipulated it in such a manner as to drain the water and the fish from the shell," said Mr Allen.
The team has since seen another dolphin - a male dubbed William the Concherer - using the "conching" technique, and their research is published in the journal Marine Mammal Science.
Mr Allen said it was possible that the dolphins randomly picked up empty conches in the hope a fish was hiding inside.
"But we think it is far more likely the fish goes into the shell seeking refuge during a pursuit."
The dolphins in Shark Bay also use sponges as soft, protective "gloves" to shield their snouts as they dig around for food on the sea floor - a skill that is passed down by mothers to their offspring.
Another foraging technique called "kerplunking" is also common, in which the dolphins scare fish out of the sea grass by slapping their tails to produce bubbles.
Sitting in a restaurant (Walvis Bay, Namibia) which is on poles partially in the sea and on a nice day the windows are open. My wife and I saw two Dolphins swim apart from each other about 50 Meters. They then swam at speed towards each other and passed within a meter. The resulting percussion between their bodies produced a fan of silvery fish which glinted like a chandelier in the sunlight. The fan collapsed back into the sea, the fish stunned. The Dolphins turned back and scooped up their lunch.
They didn't do this once they did it throughout my meal, so I had lunch and a fantastic show.
I commented to the restaurant owner that I believe these two were trained for the benefit of putting bums on seats.