Bunbury dolphins serve up calamari for dinner
A TEAM OF researchers studying Bunbury’s bottlenose dolphin population has observed the animals demonstrating unique and complex feeding habits that have only been recorded in two other places around the world.
The same population recently made headlines when the adult females were found forming a nursery in Bunbury’s protected inner waters, about 175km south of Perth, but further findings published in the Australian Journal of Zoology show that is not their only unique trait.
The findings were a happy accident – when carrying out monthly transects to determine abundance and home range of the animals, researchers observed the rare behaviour.
“It’s absolutely amazing,” Dr Kate Sprogis, lecturer at Murdoch University, said. “It’s pretty exciting when it happens.”
Five-star feast
Occupying a wide range of habitats around the world, bottlenose dolphins enjoy a variety of oceanic and bottom-dwelling fish species in their diet, but it is their method of eating cuttlefish that has researchers excited.
“Instead of just catching a fish and swallowing it, it’s done in several steps – so it’s a more complicated way of handling their prey,” said Kate. “And it’s really cool because it’s only been similarly documented in two other places in the world.”
There are about six steps in the process, which sees the dolphins catch the cuttlefish, before bringing it to the surface to begin its five-star feast.
Upon surfacing, the dolphins swiftly bite off the animal’s head and tentacles, leaving all but the body, then they squeeze out the ink.
And this is where things get interesting – the dolphins have then been observed pushing their mouth into the cuttlefish’s empty body cavity, before doing a tail-up dive to the depths.
Due to the turbid temperate waters, underwater footage of the next step has not yet been obtained, but researchers believe they use the opening motion of their mouth to break off the thin top layer of the cuttlefish, releasing the cuttlebone.
“Then we actually see the cuttlebones float to the surface,” Kate explained.
Unique preparation method
Although similar behaviour has been recorded in Portugal and Adelaide, the Bunbury dolphins’ method appears to be completely unique.
In Portugal, once eating the head and tentacles, the dolphins discard the cephalopod’s body, while in Adelaide they scrape the cuttlefish body along the seafloor to release the cuttlebone.
The unusual behaviour was observed repeatedly for almost a decade – during research funded by the South West Marine Research Program, led by the Murdoch University Cetacean Research Unit and based at the Bunbury Dolphin Discovery Centre – providing a wealth of data and sparking interest for future research.
“We’ve got all of these above-water observations of 15 individuals doing it – some of them feeding multiple times,” Kate said.
“We’d really love to know more about the cuttlefish and how important the cuttlefish are for the diet of the dolphins, because out of the 15 dolphins we saw feeding on cuttlefish, 12 of them were adult females.”
How to prepare cuttlefish, à la dolphin
Step 1: Select the cuttlefish of your choice and go for the kill – be careful not to let them fool you with their mimicry.
Step 2: Bring it to the surface – this is where the fun begins.
Step 3: Nip off the head and tentacles (pay attention not to bite the body, we’re saving that for later).
Step 4: Once you are left with the cuttlefish’s juicy centre, tightly squeeze it between your teeth – forcing the unpalatable black ink into the ocean.
Step 5: Now secure the cuttlefish over you mouth – you don’t want to lose it. Take a deep breath and tail-up dive into the depths.
Step 6: Open your mouth to break the skin and release the cuttlebone (they’re crunchy and unappetising).
Voila! Dig into the tender flesh and enjoy. Served best with a dash of sea salt.
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