A dolphin in Western Australia has bitten off more than it can chew. An attempt to eat a large octopus turned fatal when its airway was obstructed by a mass of tentacles.
The Indo-Pacific bottlenose dolphin – known as “Gilligan” to researchers in the area – was found dead on Stratham Beach near the port city of Bunbury in August 2015. Octopus arms were seen hanging out of the side of its mouth.
A post-mortem examination revealed one octopus tentacle extending down the dolphin’s oesophagus, and the other seven stuck in the back of its throat. The tentacle suckers were gripping the throat walls and had blocked off the airway, causing the dolphin to suffocate.
The tentacles belonged to a Maori octopus (Macroctopus maorum), the largest species of octopus found in Australian waters and the third largest in the world.
It is not unusual for bottlenose dolphins to feed on octopuses, but they normally break the body and tentacles into smaller pieces first using a “shake-and-toss” method. Shaking the octopus helps to kill it and tear it apart, while tossing prevents it from latching on and also weakens the suckers.
Down in one
Gilligan’s downfall was trying to swallow the 2.1-kilogram octopus whole without proper preparation, says Nahiid Stephens at Murdoch University in Perth, Western Australia, who performed the post-mortem. “We assume it simply wasn’t broken up adequately,” she says.
It would not be the first dolphin to make this mistake, Stephens says. Park rangers along the coast of Western Australia have described similar octopus-related deaths in dolphins and sea lions, she says.
Dolphins in other parts of the world have also had a hard time with octopus prey. For example, in 2012 a bottlenose dolphin in Greece was observed with an octopus clasped to its genitals.
But even though hunting octopuses is risky, there are also benefits. Large, muscular octopuses provide a robust meal full of high-quality proteins. They are also easier to catch than fish, because they tire quickly during pursuit, especially after they’ve finished breeding.
“Their consumption must generally be a risk worth taking, although it did not play out well in this individual’s case,” says Stephens.
Journal reference: Marine Mammal Science, DOI: 10.1111/mms.12420