The haunting sounds of bowhead whales, which sing their songs under Arctic ice through long, dark polar winters, have been recorded in unprecedented detail.
The recordings reveal a vocal repertoire every bit as rich as better-studied humpback and sperm whales, and hint at complex social organizations and lifestyle patterns hidden until now by the bowheads' extreme remoteness.
"We know relatively little about bowhead whales. A lot of that has to do with the fact that they're Arctic whales, found in the high, ice-covered north," said oceanographer Kate Stafford of the University of Washington. "This data gives us a window into a world that's largely inaccessible."
What little scientists do know about bowheads is fascinating. Second only to blue whales in size, they're highly social and extraordinarily long-lived: 19th-century harpoons have been recovered from their bodies, and some bowheads alive today may have been swimming when Thomas Jefferson was President.
Hunted nearly to extinction, bowhead populations have rebounded since the 1960s, giving scientists a chance to study them. Late in the summer of 2008, Stafford and colleagues dropped two underwater microphones into the icy waters of the Fram Strait, between Greenland and Norway, where a handful of bowhead sightings were reported over the last several decades.
Stafford's team hoped merely to catch a few sounds, a stray grunt or moan. Instead, as described in a study published July 31 in Endangered Species Research, they heard a veritable choral symphony.
Between November and late April, hardly an hour passed without the microphones picking up a song. The whales sang for five months straight, and their songs proved unexpectedly rich: No fewer than 60 distinctive types were identified, surpassing in sheer diversity the range of any other baleen whale species.
Unlike extensively studied sperm and humpback whale vocalizations, which can be analyzed in some detail – researchers have described sounds that appear to signify names and clan affiliation, between-whale conversations and cultural patterns of learning – bowhead interpretation is in its infancy.
Individual whales might sing a few songs, or a great many. Juveniles and adults could have different repertoires. So might males and females. Songs could pass between generations or across groups. They could convey the same types of information heard in other whales, or mean something else altogether.
"We just don't have enough data," said Stafford, who explained that recorders hardy enough to survive months of Arctic immersion have only existed for a few years. "For humpbacks and sperm whales, that work goes back decades. For bowheads, we're talking a couple years. But there's similarly neat stuff going on."
Stafford suspects some songs involve navigation, helping bowheads coordinate over long distances, and some almost certainly involve mating. The sheer volume of songs also seems linked to the nature of polar winters, which plunge Arctic oceans into icebound, near-total darkness for almost five straight months.
That's precisely when the bowheads sang so richly. Stafford's recordings might represent a bowhead bacchanal. "I don't want to be anthropomorphic, but they're spectacular," she said. "They are loud, and they go on and on."
Citation: "Spitsbergen’s endangered bowhead whales sing through the polar night." By Kathleen M. Stafford, Sue E. Moore, Catherine L. Berchok, Øystein Wiig, Christian Lydersen, Edmond Hansen, Dirk Kalmbach,and Kit M. Kovacs. Endangered Species Research, July 31, 2012.
