Belugas potentially communicate through manipulation of forehead fat blobs

The beluga whale is expressive, particularly when it comes to the fat deposit on its forehead known as the "melon".

Researchers have compiled an illustrative guide to the various expressions that captive belugas (Delphinapterus leucas) seem to display with their incredibly flexible melon, which aids in directing sound waves for echolocation.

Through the use of muscles and connective tissue, belugas can manipulate the melon in several ways – they can protrude it until it overshadows their lips, flatten it against their skull, raise it to resemble a top hat, and jolt it such that it wobbles.

"If this doesn’t demand attention, then nothing does," states animal behaviorist Justin Richard from the University of Rhode Island in Kingston. "It’s akin to observing a peacock displaying its plumage."

Prior to becoming a researcher, Richard served as a beluga trainer at the Mystic Aquarium in Connecticut for ten years, during which time he developed a close relationship with these elusive creatures. "As a trainer, I was already aware that the shapes had some significance," claims Richard. "However, no one had been able to collate enough observations to make sense of it."

In a year-long study spanning 2014-2015, Richard and his team documented the interactions among four belugas at the Mystic Aquarium. Their analysis showed that the belugas displayed five unique melon shapes – flat, lift, press, push, and shake, at an averaged rate of nearly two expressions per minute during social interactions. The findings were published in Animal Cognition on March 2.

The team is still uncertain whether these shapes are mindful gestures or subconscious reflections of the beluga's emotions. Yet a majority of the expressions (93%) took place within the sightline of another beluga, leading Richard to hypothesize that these are most likely deliberate signals or means of communication.

Expressions such as shake and press appear to be linked to courtship and mating behaviour, while others like flat are less discernible. "There are probably some subtleties that hold significance for them but are hard for us to notice," notes Richard.

The team validated its findings in a larger captive population of 51 belugas at MarineLand Canada in Niagara Falls, who displayed the same melon shapes as those at Mystic.

These five shapes may just be the beginning of understanding this Arctic cetacean's communication, suggests Richard. Further research is required to understand how belugas manipulate their melody in the wild, particularly during critical behaviours such as group hunting or calf rearing.

Malin Lilley, a comparative psychologist who studies marine mammal behaviour and cognition at Texas A&M University–Central Texas in Killeen, states that these findings present a common language that researchers can expand on as they attempt to decipher beluga communications. Labelling these expressions is not only important for understanding belugas, Lilley points out, but it also gives words for the squishy expressions that have always delighted beluga researchers.

Both Richard and Lilley are interested in determining how these expressions correlate with beluga vocalizations. The myriad of beluga whistles, chirps, squeals, and clicks have earned them the nickname "canaries of the sea."

Richard theorises that if such visual displays occur among wild belugas in the opaque Arctic waters, then they are transmitting significant information. "The fact that they dedicate so much time to it," he says, "indicates that there’s more to it."