SAN DIEGO — Researchers in San Diego strapped cameras to dolphins to delightful effect this year, producing fascinating video of the animals hunting down fish and even sea snakes.
Ridgway and study co-authors Dianna Samuelson Dibble and Mark Baird paired cameras with hydrophones, producing synced video and audio. The researchers said it was the first time dolphins have been recorded capturing and eating live native fish in that manner.
The dolphins enlisted in this task were part of the U.S. Navy Marine Mammal Program, in which the animals are trained to search for undersea mines and perform other tasks. In this case, their job was simple: Swim around and catch dinner.
The dolphins had themselves a feast.
Swimming freely in San Diego Bay, one dolphin caught 69 fish. Two others consumed a whopping 135 fish in a sea water pool. Researchers observed an additional two dolphins in open water sessions in the Pacific Ocean.
One of the ocean hunters baffled researchers with some highly unusual catches: It gobbled down eight — yes, eight — yellow-bellied sea snakes.
There’s hardly any precedent for dolphins snacking on the venomous serpents, the researchers wrote. They were so skeptical that, at first, they looked for species of fish they could possibly mistake for snakes. Video confirmed their initial impression, however, and fortunately the hungry dolphin was no worse for the wear.
The videos are fun for the casual viewer, but they also provide valuable insight for marine mammal experts. Brittany Jones, a scientist who worked closely with Ridgway while he and his co-authors compiled the study, pointed out some of the research highlights in a phone interview with FOX5SanDiego.com this week.
For one, the syncing of audio and video provided unprecedented context for the noises dolphins make while they’re foraging. Researchers tracked the pace of the dolphins’ clicks as they navigated by echolocation, growing more frenetic as they neared their next meal. Audio also confirmed the timing of a sort of “victory squeal,” which comes after one of the animals catches its prey.
The video provided its own insights, Jones said. Researchers tracked the dolphins’ eye movements frame by frame, determining that dolphins were hunting by sight in addition to sonar clicks.
The videos also highlighted dolphins’ “vacuum-like” ability to swim with a fish just inside their jaws, repositioning their prey occasionally before suddenly sucking it down.
The weirdest moment? Certainly the dolphin snacking on sea snakes.
“That was definitely surprising,” Jones said, laughing. “Fortunately it was fine.”
Jones said the study will have “trickledown effects forever,” providing important insights on exactly how dolphins navigate their space and track down prey. That can help ensure that policies governing things like ocean noise pollution are based on science. Riding along with the animals is the best way to know what will or won’t disrupt their natural patterns.
“What a unique opportunity that we would be able to get this up-close view of dolphins while they are foraging in the open ocean,” the scientist said.
Jones said the study is also a fitting final piece in the legacy of Ridgway, a highly distinguished veterinarian and scientist known as the “father of marine mammal medicine” — or simply, “the dolphin doctor.”
Jones said she was lucky to receive mentorship from Ridgway, and that strapping cameras to dolphins was exactly the kind of outside-the-box thinking that made him an innovative and accomplished researcher.
He died in July, shortly after the study’s conclusion. A month later, his work was published, spreading joy online and sparking intrigue in the scientific community.
“We are all very excited to see this manuscript published as we celebrate Dr. Ridgway’s life and legacy and his unparalleled contributions to scientific literature,” Jones wrote, in a statement reflecting on her mentor’s legacy. “He lives on through these works and will continue to educate and inspire future scientists and veterinarians for generations.”