Belugas may communicate by warping a blob of forehead fat

Whales in captivity can mold their “melon” into at least five different shapes

A beluga whale looks toward the camera, its forehead bulging out prominently

Beluga whales like this one at Connecticut’s Mystic Aquarium sport a blob of forehead fat called a “melon.” The cetaceans contort the melon into different shapes, possibly to communicate with each other.

Paul Souders/Getty Images

The beluga whale wears its heart on its sleeve — or rather, its forehead.

Researchers have created a visual encyclopedia of the different expressions that belugas (Delphinapterus leucas) in captivity seem to make with their highly mobile “melon,” a squishy deposit of fat on the forehead that helps direct sound waves for echolocation.

Using muscles and connective tissue, belugas can extend the melon forward until it juts over their lips like the bill of a cap; mush it down until it’s flattened against their skull; lift it vertically to create an impressive fleshy top hat; and shake it with such force that it jiggles like Jell-O.

“If that doesn’t scream ‘pay attention to me,’ I don’t know what does,” says animal behaviorist Justin Richard of the University of Rhode Island in Kingston. “It’s like watching a peacock spread their feathers.”

A collage of five images showing five different contortions of a blob of fat on a beluga whale's head
Belugas make at least five distinct shapes with their melons, researchers say. Four of the shapes are shown in this lineup. Top row, from left: flat, lift, press. Bottom row: push and no shape.J.T. Richard (CC BY 4.0 DEED)

Before Richard became a scientist, he spent a decade as a beluga trainer at the Mystic Aquarium in Connecticut, working closely with the enigmatic animals. “Even as a trainer, I knew the shapes meant something,” Richard says. “But nobody had been able to put together enough observations to make sense of it.”

Over the course of a year, from 2014 to 2015, Richard and colleagues recorded interactions between four belugas at the Mystic Aquarium. Analyzing the footage revealed that the belugas make five distinct melon shapes the scientists dubbed flat, lift, press, push and shake. The belugas sported an average of nearly two shapes per minute during social interaction, the team reports March 2 in Animal Cognition.

It’s not clear whether the shapes are intentional gestures or unconscious reflections of the beluga’s emotional state. But 93 percent of the shapes occurred within another beluga’s line of sight, so Richard suspects they’re probably purposeful signals or communications.

Shake and press seem to be associated with courtship and sexual behavior, while others like flat have proven more difficult to parse. “There are probably some gradations that are meaningful to them that are difficult for us to pick out,” Richard says.   

Two belugas at an aquarium bob their heads up and down, shaking their blobs of forehead fat — called melons — at one another. One of five distinct melon shapes that the whales make, “shake” seems to be associated with courtship and sexual behaviors, a new study suggests.

The team has validated the findings in a larger captive population — 51 belugas at MarineLand Canada in Niagara Falls exhibit the same melon shapes that the Mystic whales do.

The five shapes documented in the study may be the tip of the iceberg for this Arctic cetacean, Richard says. Scientists have yet to track how belugas use their melon in the wild, especially during important behaviors such as group foraging or mothers interacting with calves.

The findings establish a shared vocabulary that researchers can build on as they work to decode beluga communication, says Malin Lilley, a comparative psychologist at Texas A&M University–Central Texas in Killeen who studies marine mammal behavior and cognition. Not only is labelling the shapes key for understanding belugas, Lilley says, but also it’s just plain cool to have words to describe the delightfully squishy expressions she’s seen in her years of beluga research.

Richard and Lilley are both eager to learn how the shapes interact with beluga vocalizations. The whales’ near-constant stream of whistles, chirps, squeals and clicks have earned belugas the moniker “canaries of the sea.” 

If wild belugas make this kind of visual display in murky Arctic waters, then “there must be important information that’s being transmitted,” Richard says. “There’s got to be a reason they spend so much time doing it.”

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