Dolphins' fish-catching tactic may be spreading
Source: Agencies |
August 30, 2011, Tuesday
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Print Edition
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DOLPHINS in one western Australian population have been observed holding a large conch shell in their beaks and using it to shake a fish into their mouths - and the behavior may be spreading.
Researchers from Murdoch University in Perth, Western Australia, were not quite sure what they were seeing when they first photographed the activity, in 2007, in which dolphins would shake conch shells at the surface of the ocean.
"It's a fleeting glimpse - you look at it and think, that's kind of weird," said Simon Allen, a researcher at the university's Cetacean Research Unit. "Maybe they're playing, maybe they're socializing, maybe males are presenting a gift to a female or something like that, maybe the animals are actually eating the animal inside."
But researchers were more intrigued when they studied the photos and found the back of a fish hanging out of the shell, realizing that the shaking drained the water out of the shells and caused the fish that was sheltering inside to fall into the dolphins' mouths.
A search through records for dolphins in the eastern part of Shark Bay, a population that has been studied for nearly 30 years, found roughly half a dozen sightings of similar behavior over two decades.
Then researchers saw it at least seven times during the four-month research period starting this May, Allen said, adding, "There's a possibility here - and it's speculation at this stage - that this sort of change from seeing it six or seven times in 21 years to seeing it six or seven times in three months gives us that tantalizing possibility that it might be spreading before our very eyes."
The Shark Bay dolphin population is already unusual for having developed two foraging techniques, one of which involves the dolphin briefly beaching itself to grab fish after driving them up onto the shore. The other is "sponging" - in which the dolphins break off a conical bit of sponge and fit it over their heads like a cap, shielding them as they forage for food on the sea floor.
Researchers from Murdoch University in Perth, Western Australia, were not quite sure what they were seeing when they first photographed the activity, in 2007, in which dolphins would shake conch shells at the surface of the ocean.
"It's a fleeting glimpse - you look at it and think, that's kind of weird," said Simon Allen, a researcher at the university's Cetacean Research Unit. "Maybe they're playing, maybe they're socializing, maybe males are presenting a gift to a female or something like that, maybe the animals are actually eating the animal inside."
But researchers were more intrigued when they studied the photos and found the back of a fish hanging out of the shell, realizing that the shaking drained the water out of the shells and caused the fish that was sheltering inside to fall into the dolphins' mouths.
A search through records for dolphins in the eastern part of Shark Bay, a population that has been studied for nearly 30 years, found roughly half a dozen sightings of similar behavior over two decades.
Then researchers saw it at least seven times during the four-month research period starting this May, Allen said, adding, "There's a possibility here - and it's speculation at this stage - that this sort of change from seeing it six or seven times in 21 years to seeing it six or seven times in three months gives us that tantalizing possibility that it might be spreading before our very eyes."
The Shark Bay dolphin population is already unusual for having developed two foraging techniques, one of which involves the dolphin briefly beaching itself to grab fish after driving them up onto the shore. The other is "sponging" - in which the dolphins break off a conical bit of sponge and fit it over their heads like a cap, shielding them as they forage for food on the sea floor.
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