*Update: Click here for updated version of this story with video
Blue whales are being seen fairly frequently this summer off Southern California, but the planet's largest creatures are almost never heard vocalizing above the surface.
On Tuesday off Long Beach, however, an NBC crew and biologists aboard the Christopher, during a special morning run, witnessed this extremely rare phenomenon as a large blue whale surfaced alongside the vessel and, with much of its head above the surface, issued a deep, low-pitch groan that lasted nearly 10 seconds.
"We heard it through the air, loud and clear," said Alisa Schulman-Janiger, an American Cetacean Society researcher. "It was a strange, alien sound. It really was an extraordinary thing."
Blue whales communicate, for up to hundreds of miles, with low-pitched vocalizations. The vocalizations can sometimes be picked up via submerged hydrophones, but the majestic leviathans, which can measure 100 feet and weigh 150 tons, are not known for making sounds other than those associated with breathing while at the surface.
Those aboard the Christopher -- a naturalist from the Aquarium of the Pacific also was aboard -- were treated to blue whale vocalization twice, as the same whale repeated this behavior on the other side of the boat.
Afterward, Schulman-Janiger phoned John Calambokidis, one of the world's top blue whale scientists. He told her that in his extensive study of blue whales around the world, he had never heard above-surface vocalization from a blue whale.
"I told the reporters on the boat, "You don't understand but you will never see this type of behavior again,' " Schulman-Janiger said.
About 2,000 blue whales -- part of an endangered global population of roughly 10,000 -- spend part of each summer and fall off California gorging on tiny shrimp-like krill. A single blue whale can consume four tons of krill, which flourishes in massive blooms in nutrient-rich areas where upwelling occurs, per day.
The whales feed almost constantly but the four whales alongside the Christopher, perhaps having had their fill, were clearly cavorting and possibly engaging in courtship behavior. They lunged, or raced across the surface, at times lifting their heads and chin-slapping in what seemed a game of follow the leader. Typically, it's a female in the lead.
It was during a break that the largest whale paused and was "like a log in the water," Schulman-Janiger said, when it began to vocalize. There were no bubbles from below and was no movement of the blow holes, which were clearly visible. The sound appeared to have come from deep within.
Schulman-Janiger used terms such as "otherworldly" and "spooky" while trying to describe the sound, but judging from her enthusiasm it was still music to the ears.
(Footage of the encounter aired Wednesday on the Nightly News.)
-- Blue whale images courtesy of Alisa Schulman-Janiger