Up shut and private: Dolphin POV caught on digital camera whereas trying to find tasty fish

Enlarge / “I spy with my dolphin eye… one thing that appears like prey!”

There’s not often time to jot down about each cool science-y story that comes our means. So this 12 months, we’re as soon as once more operating a particular Twelve Days of Christmas sequence of posts, highlighting one science story that fell by way of the cracks in 2022, every day from December 25 by way of January 5. Immediately: Scientists hooked up video cameras onto dolphins to seize the sights and sounds of the animals as they hunted for prey to study extra about their feeding conduct.

Scientists hooked up GoPro cameras to 6 dolphins and captured the sights and sounds of the animals as they hunted and devoured varied species of fish—even squealing in victory on the seize of child sea snakes, in keeping with an August paper printed within the journal PLoS ONE. Whereas sound and video has beforehand been recorded for dolphins discovering and consuming useless fish, per the authors, that is the primary footage combining sound and video from the dolphins’ standpoint as they pursued stay prey whereas freely swimming. The audio component enabled the scientists to study extra about how the dolphins communicated whereas searching.

Sam Ridgway and his colleagues on the Nationwide Marine Basis in San Diego, California, have performed earlier analysis on dolphins. They thought they might study much more concerning the animals’ searching and feeding methods utilizing cheap business GoPro cameras to document sounds in addition to visuals. The excessive frames per second (60, 90, or 120 FPS) enabled them to look at modifications in conduct body by body.

The US Navy trains captive dolphins to determine mines, amongst different makes use of. (Though the dolphins are technically free to swim away, most “select” to stay round.) Two of these dolphins—recognized as S and Ok—had been led out by their coach’s boat into San Diego Bay. There they got free rein to forage for meals for 50 minutes. Footage was captured for 15 such outings for dolphin S, and 5 outings for dolphin Ok. Dolphins B and T wore cameras whereas swimming in an above-ground 6×12 meter sea water pool. Stay Pacific mackerel, sardines, and Northern anchovies from a stay bait provider had been let loose within the pool so  B and T might hunt. Lastly, dolphins Y and Z had been filmed by the way capturing prey whereas freely swimming within the open ocean.

Over the course of the research, S caught 69 fish and Ok caught 40 fish, together with noticed sand bass, barred sand bass, smelt, yellowfin croaker, California halibut, and pipefish. The fish had been captured each close to the floor (notably smelt) and, extra often, on the ocean ground, lurking in patches of vegetation. The audio revealed that S, for instance, would buzz and squeal to seek out the hidden fish within the latter state of affairs, gobbling up a mouth filled with the sediment, swallowing the fish and ejecting the sediment and any plant materials again into the water. (One fish did handle to flee the dolphin jaws of loss of life and swim away.)

 

Among the many shocking findings was the power of all of the dolphins to open their higher and decrease lips to suck prey into their mouths. That is how dolphins B (collected within the Nineteen Eighties within the Gulf of Mexico) and T captured their fish within the sea water pool, utilizing a aspect swipe movement of the top. There have been a couple of examples of so-called “ram feeding”—wherein prey is quickly overtaken and clasped within the jaws earlier than being swallowed—particularly when searching close to the floor, however most feeding occasions primarily used the suction methodology.

T had been stranded on a Florida seashore as a child in 2013 and raised at Sea World of Florida, so T had by no means been noticed catching stay fish earlier than. However after watching B seize prey, T caught on and started searching with glee. “His captures had been attended by a lot squealing,” the authors wrote.

Dolphins Z and Y had been additionally recorded squealing in victory whereas capturing prey, and Z truly consumed 8 (probably new child) yellow-bellied sea snakes—an uncommon selection, since dolphins have not beforehand been identified to feed on sea snakes (though they’ve been noticed enjoying “cat and mouse” with sea snakes). “Maybe the dolphin’s lack of expertise in feeding with dolphin teams within the wild led to the consumption of this outlier prey,” the authors wrote. Fortuitously, “Our dolphin displayed no indicators of sickness after consuming the small snakes.”

DOI: PLoS ONE, 2022. 10.1371/journal.pone.0265382  (About DOIs).

Dolphin Z catching sea snakes within the Pacific Ocean with head jerks and a victory squeal. Credit score: Ridgway et al., 2022