ANCHORAGE, Alaska >> It’s not America’s Top 40, but it’s a cutting edge song.

Federal marine biologists for the first time have recorded singing by one of the rarest whales on the planet, the North Pacific right whale.

National Oceanic and Atmospheric Administration researchers used moored acoustic recorders to capture repeated patterns of calls made by male North Pacific right whales.

It’s the first time right whale songs in any population have been documented, said NOAA Fisheries marine biologist Jessica Crance today from Seattle. She spoke to southern right whale and North Atlantic right whale experts to confirm that singing had not previously been documented.

Researchers detected four distinct songs over eight years at five locations in the Bering Sea off Alaska’s southwest coast, Crance said.

Only about 30 of the animals remain. Whalers nearly wiped out the slow-moving whales, which remain buoyant after they are killed.

Humpback, bowhead and other whales are known for their songs. During a field survey in 2010, NOAA Fisheries researchers first noted weird sound patterns they could not identify.

“We thought it might be a right whale, but we didn’t get visual confirmation,” Crance said.

The researchers reviewed long-term data from acoustic recorders and noted repeating sound patterns. Seven years of frustration followed, Crance said, as they could never positively confirm that the sounds were coming from the scarce right whales.

The breakthrough came in 2017. Crance and her team heard one of the whale songs in real time from the acoustic recorders on buoys. Researchers can receive sound from up to four buoys at once and point them toward the source. That allowed them to triangulate the position of the whale making the song. From previous surveys and genetic studies, they identified it as a male right whale.

“It was great to finally get the confirmation when we were out at sea that yes, it is a right whale, and it’s a male that’s singing,” Crance said.

Right whales make a variety of sounds. A predominant call sounds like a gunshot. They also make upcalls, downcalls, moans, screams and warbles.

To be a song, the sounds have to contain rhythmically patterned series of units produced in a consistent manner to form clearly recognizable patterns, Crance wrote in a paper for the Journal of the Acoustical Society of America.

“It’s a series of sounds that are reproduced in a stereotyped, regular manner that are repeated over and over,” she said.

Structurally, in timing and number of sounds, right whale songs resemble those of the Atlantic walrus, she said. Both are filled with impulses, with walruses substituting knocking sounds for gunshot sounds.

The discovery almost raises more questions than answers, Crance said.

“Is it the only population to sing or does it occur in other species and populations?” she asked.

“It could be that there are so few of them left, they feel the need to call more frequently or sing,” Crance said. “This is entirely speculation, but perhaps they’re copying humpbacks, a little bit. Our right whales are frequently seen associating with humpbacks.”

The remote Bering Sea makes studying right whales a challenge. Their range remains unknown. Some years NOAA Fisheries researchers see no right whales on their summer voyages. They spotted what they believe was a juvenile in 2017 but the last Bering Sea mother-calf pairing was seen in 2004, Crance said.

A singing male may be trying to attract a female, she said.

“With only 30 animals, finding a mate must be difficult,” Crance said.