Scientists attached GoPro cameras to six dolphins and captured the sights and sounds of the animals as they hunted and devoured various species of fish—even squealing in victory at the capture of baby sea snakes, according to an August paper published in the journal PLoS ONE.

While sound and video has previously been recorded for dolphins finding and eating dead fish, per the authors, this is the first footage combining sound and video from the dolphins' point of view as they pursued live prey while freely swimming. The audio element enabled the scientists to learn more about how the dolphins communicated while hunting. Sam Ridgway and his colleagues at the National Marine Foundation in San Diego, California, have conducted previous research on dolphins. They thought they could learn even more about the animals' hunting and feeding strategies using inexpensive commercial GoPro cameras to record sounds as well as visuals. High frame rates per second (60, 90 or 120 frames per second) allowed us to observe changes in motion from frame to frame. The US Navy trains captive dolphins to recognize landmines, among other things. (Technically, dolphins can swim freely, but most "prefer" to stay nearby.) Two of these dolphins, designated S and K, were taken to San Diego Bay by boat by their trainers. There they were given 50 minutes of complete freedom to get food. 15 episodes of Dolphin S and 5 episodes of Dolphin K were filmed. Dolphins B and T wore cameras and swam in a 6x12 m saltwater pool above ground. Live-bait vendors' live Pacific mackerel, sardines, and northern anchovies were set free for B and T to hunt. Lastly, dolphins Y and Z were caught on video as they accidentally caught prey while swimming free in the open sea. During the study, S. caught 69 and K. caught 40, including spotted perch, striped sand perch, smelt, yellowfin tuna, California halibut, and igloo. Fish are caught near the surface (especially in the smelt) and more often at the bottom, hiding in areas with vegetation. The audio revealed that S, for example, would buzz and squeal to find the hidden fish in the latter scenario, gobbling up a mouthful of the sediment, swallowing the fish, and ejecting the sediment and any plant material back into the water. (One fish did manage to escape the dolphin jaws of death and swim away.) Among the surprising findings was the ability of all the dolphins to open their upper and lower lips to suck prey into their mouths. That's how dolphins B (collected in the 1980s in the Gulf of Mexico) and T captured their fish in the seawater pool, using a sideswipe motion of the head. There were a few examples of so-called "ram feeding"—in which prey is rapidly overtaken and clasped in the jaws before being swallowed—especially when hunting near the surface, but most feeding events primarily used the suction method. T had been stranded on a Florida beach as a baby in 2013 and raised at Sea World of Florida, so T had never been observed catching live fish before. However, after seeing B catch the prey, T realized it and started hunting with excitement. “His grip was accompanied by loud screams,” the author writes. Dolphins Z and Y have also been recorded screaming triumphantly while preying, and Z actually ate eight (possibly newborn) yellow-bellied sea snakes. playing "Cat and Mouse" with a sea snake). "Probably the dolphins' lack of experience feeding with dolphin packs in the wild led them to this unusual diet," the authors wrote. Luckily, "our dolphin showed no signs of illness after eating the little snake."