Read our COVID-19 research and news.

First direct observation of hunting pelican eel reveals a bizarre fish with an inflatable head

What would you get if you crossed a pelican with an eel? Probably something close to the aptly named pelican eel (Eurypharynx pelecanoides), a bizarre-looking fish with a slender body and a head that inflates like a balloon.

Because the pelican eel prefers to live between 500 and 3000 meters below the surface of tropical and temperate seas, it is seldom seen or photographed by humans. This makes it difficult to study the eel’s behavior to look for clues as to why it evolved such a strange head.

Now, researchers have made what they believe to be the first direct observation of a pelican eel hunting for prey and captured the behavior on video. Researchers piloted a submarine to a depth of 1000 meters in the Atlantic Ocean, about 1500 kilometers off the coast of Portugal near a constellation of islands known as the Azores.

The team spotted the eel not only inflating its head to form a pouch for catching prey, but also actively hunting and swimming after smaller fish. Previous research had hypothesized that the eels inflated their heads to lure their prey or to create a large hole into which food could fall out of the water column, but these studies relied on evidence from the stomach contents of dead eels. The new video evidence suggests the eels take a much more active role in finding food: exploring their surroundings, stalking prey, and inflating their heads to maximize the probability of engulfing them.

Earlier this month, another team of researchers caught a pelican eel on camera with an unmanned submarine off the coast of Hawaii. But that video shows only the inflation and deflation of the eel’s head, not its hunting behavior.

The scientists hope to record more footage of the pelican eel and other unstudied deep-sea creatures to better understand the evolutionary history of their freaky features, and how they use these unusual adaptations to survive the harsh environments deep beneath the surface.