giant snails

Theodolite Thursday: Dolphins Learn Unusual Hunting Behavior

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Yes…another new heading. From Merriam-Webster:

[A] surveyor’s instrument for measuring horizontal and […] vertical angles

This is the instrument of land surveyors. In my case, I will survey other things. ~Vic

Dolphins Unsplash Image
Photo Credit: Courtnie Tosana on Unsplash

In the crystal clear waters of Shark Bay in Western Australia, scientists have noticed bottlenose dolphins engaging in an unusual behavior. They guide fish into the empty shells of giant snails, bring the shells to the surface and, then, shake them vigorously to dislodge the prey into their open mouths like a person polishing off a bag of popcorn. That extra effort, known as shelling, gets them a guaranteed meal.

Because the dolphins […] use the shells as a trap, this is the second known case of these marine mammals using tools. The first was reported in [1984] when researchers found that bottlenose dolphins wear marine sponges like protective gloves over their beaks to forage for fish on the sea floor. Now, researchers have shown that the dolphins of Shark Bay learn shelling from their friends. It’s the first time social learning involving a tool has been discovered in these mammals and a rare example of such learning in the animal kingdom.

Dolphins Unsplash Image Two
Photo Credit: Red Charlie on Unsplash

Though scientists noticed the shelling behavior more than 10 years ago, it became more frequent following an unusual marine heat wave (PDF) off Western Australia in 2011. The high temperatures roiled Shark Bay’s ecosystem and many gastropods, including sea snails, are believed to have died. “We think the dolphins took advantage of this die-off,” says Sonja Wild, a behavioral ecologist at the Max Planck Institute of Animal Behavior. “The next season,” she says, “there was an incredible increase in shelling”, which made it possible for her to tease out how young adult dolphins learn to do it.

Wild says shelling starts among the adults [but], the more time a young dolphin spends around an accomplished sheller […], “the more likely it is to learn” the technique and pass it on to others later. Still, because dolphin calves spend more than 30,000 hours with their mothers, it’s possible that some learned the trick from their moms, [states] Janet Mann, a dolphin expert at Georgetown University. It’s considered more cognitively demanding to learn a skill like shelling from an unrelated individual because both learner and demonstrator must be socially tolerant, especially while hunting.

Virginia Morell
Science Magazine
June 25, 2020