In the video, tweezers poke a piece of octopus that is sitting on a ramp as an offering. Suddenly a snowflake moray named Qani lifts her muscular bucatini body out of the water and onto the ramp. It opens its mouth and bites the squid. The eel pauses for a moment, opens its mouth again and sucks the squid even deeper into its mouth, as if on a conveyor belt with a secret second mouth in its throat.
This particular eel mukbang for Rita S. Mehta, an evolutionary biologist at the University of California, Santa Cruz, was cinematic gold: footage showing the bite, the transport of prey with secondary jaws, and the swallow. Her team had captured plenty of footage of the eels feeding on the ramp, but none that showed the act from start to finish.
Dr. Mehta first described the second set of moray eel choppers, known as throat jaws, in 2007. When a moray eel hunts, it grasps its prey with the teeth of its outer jaw, and then its jaws leap forward from the throat and into the mouth to grab the prey and pull it deeper into the eel’s body.
Now Dr. Mehta described how snowflake eels and other moray eels use their jaws to feed on land as effectively as they do in water, according to a study published this month in the Journal of Experimental Biology.
Like many other fish, moray eels eventually dry out if they keep watering for too long. But dr. Mehta and her colleagues cite a 1979 study that suggested that the outermost layer of skin on a moray eel contains certain mucous glands that can make these eels more resistant to time on land.
And moray eels climbing out of the water did not surprise some observers. Lana Sinapayen, an artificial life researcher who grew up on the Caribbean island of Martinique, said local fishermen often caught moray eels by laying squid on shore and waiting for the eels to arrive. “You just need a solid stick to make your choice,” she wrote in an email. Dr. Sinapayen was not involved in the research, but wanted to emphasize that many locals have long known that moray eels can hunt on land.
Such behavior has long been reflected in scientific studies. A 1971 publication describes a moray eel that climbed into the same tidal pool to hunt for five days in a row.
When Dani Rabaiotti, a London-based environmental scientist, volunteered at an aquarium as a teenager, she met a moray eel who knew how to slide onto a ledge and wait to be hand-fed. “He’d learned it was easier than hanging out in the water with all the other hungry animals,” she said.
Dr. Mehta had also seen moray eels hunting ashore – they caught land crabs on a beach in Bali – but the real question of her research was what the eels did to their prey after they bit. Do the eels have to return to the water? Or could they swallow ashore?
“Fish are mostly suckers and catch prey by sucking water in their mouths,” said Peter Wainwright, a fish biomechanics expert at the University of California, Davis who previously worked with Dr. Mehta collaborated but was not involved in the new research. He added that “Moray eels have evolved away from suction feeding”.
In 2014, Dr. Mehta to train a small cohort of eels to feed on land and film them in the act. She procured snowflake moray eels from an aquarium wholesaler, and two of her former PhD students, Benjamin Higgins and Jacob Harrison, designed and installed a sand-covered plexiglass ramp in each eel tank.
For six years, Dr. Mehta and a changing group of students seven eels to eat on the ramp. By the end of the project, Kyle Donohoe, Dr. Mehta’s former lab technician and co-author of the study, developed a rigid ramp program for the eels.
Mr. Donohoe, who once worked in a lab training seals and sea lions, proved to be an extremely effective trainer. As it turns out, training an eel is similar to training a seal.
“Consistent feeding, increased chances of reinforcement and patience,” said Mr Donohoe. He taught Qani to keep moving up the ramp and feeding with tweezers in just three weeks – the fastest of any eels in the study.
Another eel named Benjen entered Dr. Mehta’s lab. Benjen, who was almost twice as long as Qani and the largest eel in the study, eventually refused to climb the ramp for the evenly measured 1.1-inch squid pieces that all other trained eels received. The mammoth moray only climbed the ramp for chunks of squid so large and disproportionate to the body of the eel that one of the newspaper’s reviewers asked that Benjen be removed from the newspaper’s statistical analysis.
“But he’s the star of the lab,” said Dr. Mehta.
In Dr. Mehta’s eyes was an unexpected finding of the experiment, the resilience of eel memory. School holidays and vacations often interrupted eel training, but Benjen remembered the ramp anyway. Dr. Mehta hopes that in the future a student will come along who wants to teach Benjen new tasks. He continues to live in the laboratory, where he still crawls onto the ramp, uninvited, and waits for large squids.