Bowhead whales are truly magnificent animals. Reaching a staggering 20 meters (65 feet) in length, they are second only in size to the iconic blue whale. Their ginormous heads, which make up around one-third of their total body length, act as sledgehammers to smash through ice up to an impressive 20 centimeters (8 inches) in thickness, although some Eskimos claim to have seen them crash through 60 centimeters (2 feet) of ice.
Discoveries of ancient harpoons embedded in their flesh suggest that these mighty animals could live to be close to 200, making them the longest lived mammal known. But perhaps their most intriguing feature is their remarkable singing ability. These animals are known to have the most impressive song repertoire of all whales, and scientists have just managed to record 12 unique songs being sung during their annual migration. Alongside hypnotizing us with their haunting singing, the discovery is helping shed light on how these mysterious creatures communicate.
Bowhead whales are tricky animals to study. They are only found in the seasonally ice-covered Northern Hemisphere, in cold Arctic waters, meaning it’s impossible to track them visually throughout the year. A much more effective strategy is to eavesdrop on them by installing underwater microphones, or hydrophones, in the ocean for extended periods of time, allowing researchers to listen in to their chatter and monitor populations.
This simple technique was employed by the authors of the latest study, who chose to focus on one particular population of bowhead whales during their annual spring migration along the coast of Alaska. These animals belong to the Bering-Chukchi-Beaufort population, one of four populations currently recognized based on their geographic distribution. This population, alongside the Eastern Canada-West Greenland population, is slowly beginning to increase after being dramatically reduced by commercial whaling in the 1600s to 1800s.
According to the study, which has been published in Marine Mammal Science, during 95 hours of recordings, 12 unique song types produced by at least 32 individuals were observed. This is the greatest number of unique songs so far recorded in this group during this particular period. Although previous work identified more than 60 unique songs, the study period was significantly longer, lasting one year.
While other whale species may be more famous for their singing abilities, such as the humpback whale, it seems that the bowhead whale has the greatest repertoire of songs. Furthermore, according to study co-author Kathleen Stafford, these whales are unique in that they change their songs both from year to year and within the year. Why bowheads exhibit this behavior is unclear, but Stafford is endeavoring to find out. What is known, however, is that these songs can be learnt from one another, and that they are probably used as social calls or a fitness display.
Scientists are also puzzled as to why these animals sing such a wide range of songs, but some believe it could be due to the growth spurt that populations are now experiencing, which is of course great news. Since hydrophones can be left in the water for over a year, it is likely that we will learn of many more unique songs in the coming years.
[via BBC Earth and Marine Mammal Science]
1
