Interestingly, the dolphin population to which Gilligan belonged — located near the Western Australian town of Bunbury — has been observed taking extra precautions to ensure that its octopus prey is safe to eat. In another paper for Marine Mammal Science, Kate Sprogis of the Murdoch University Cetacean Research Unit and her colleagues described detailed observations of dolphins from this population shaking octopus prey above water and tossing it through the air in apparent attempts to remove the head and mantle, tenderize the arms to render them inactive, and break the octopus into smaller pieces for easier consumption.
“The dolphin needs to make sure the octopus arms are completely limp before swallowing the octopus,” Sprogis explained in an email to Seeker. “The dolphin can raise its body half way out of the water and shake/toss the octopus several meters into the air forwards, and does this consecutively over and over (sometimes more than 15 times). This would be energetically exhausting because they do it so quickly. It is a sight to see them handling the octopus.”
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While these are the only dolphins known to display this behavior with octopuses, other whale and dolphin species employ similar techniques with different prey. Bottlenose dolphins shake and toss fish and break apart giant cuttlefish into manageable pieces, and orcas shake sea lions and toss stingrays and small dolphins through the air.
Sprogis does not know how often dolphins off Bunbury die because they failed to adequately prepare their octopus meal.
“If the dolphin sinks, or washes up onto the remote beaches in the study area, then we won't know the cause of death (just that the dolphin hasn't been sighted in a long time),” she said.
She and her colleagues are on the water watching the dolphins nearly every month, but although they had not seen Gilligan shaking and tossing octopuses, Sprogis said she assumed that Gilligan knew how to do so. But, in the same way that humans know how to eat and still sometimes contrive to choke on their food, so Gilligan likely simply misjudged his ability to swallow his meal.
“It’s a risky behavior with large prey,” Sprogis noted.
And sometimes, the risk doesn’t pay off.
WATCH: Understanding the Weird Anatomy of an Octopus