“If verified … it could completely change how we view and interpret whale behavior on the breeding grounds.”

It’s been more than a decade since biologist Dr. Jim Darling first heard heartbeatlike sounds off the coast of Maui, Hawaii, on Feb. 12, 2005, but these mysterious noises have engulfed his studies with Whale Trust Maui ever since.

“I did not know what they were, and my initial reaction was to look around for a source,” says Darling, who searched the sky for a passing helicopter and wondered if a submarine was lurking below.

The sounds were recorded again in 2013 — this time within a few yards of a pair of adult humpback whales, which are more well-known for their songlike vocalizations. Human hearing ranges from 20 Hz to 20 kHz, making the low 40 Hz sounds difficult to hear in anything but perfectly calm ocean conditions.

If the sounds are proved to be coming from humpbacks, “it would mean there is another channel of communication occurring on the breeding grounds that, to date, we have not been aware of in our interpretation of behavior patterns,” says Darling.

While no one is certain if the thumping noise is coming from humpbacks, the circumstantial evidence has stimulated interest among scientists. Whale Trust Maui, a scientific research nonprofit, wrote on its website: “If verified … it could completely change how we view and interpret whale behavior on the breeding grounds.”

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Darling added that if humpbacks are the source, he would then want to look at typical interactions with the whales to see if this communication could answer some of his questions about the whales’ behavioral patterns.

“Confirming that humpbacks are making the sounds is probably just going to require a larger sample of the sounds, and if in each case they are recorded within tens of meters of humpbacks — eventually the circumstantial evidence will suffice,” Darling said.

Whale Trust Maui will also see if others recording marine noises in Hawaii have heard similar heartbeat sounds during times of the year when humpbacks — which visit Hawaiian waters annually from November to May — are not in the local waters.