New research suggests that male fin whales change their songs over time - contesting previous theories that these species are just one-track animals.
Previous theories believed that the male fin whale sings only one rhythm over their lifetimes, unique to the same members of the particular group. However, researchers from the Naval Information Warfare Center Pacific and the National Marine Mammal Foundation found out that these marine mammals actually sing different songs, which are carried across the ocean when fin whales migrate.
Researchers believe that the structure of these different songs could offer insight into the behavior and changes in their population and hopefully support efforts for the protection and conservation of their species. Details of their study are submitted in the journal Frontiers in Marine Science.
Shifting Songs for Fin Whales
The research team used hydrophones - microphones submerged deep in the water - to record the songs and the locations of 115 fin whale encounters over six years (2011 - 2017) in Kauai, Hawaii. Their study covered more than 50,034 recorded notes Dr. Regine Guazzo, a member of the research team from NIWC Pacific, explains that the sounds are recorded on more than one hydrophone. This allows them to use a triangulation method to pinpoint the source of the signal, then determine the whales' position. They then illustrated in the study how the same fin whale most likely created different songs - computing for the source of the songs from the same location.
"There is still a lot of uncertainty around the fin whale population size and structure in the North Pacific," explains Dr. Tyler Helble, also from NIWC Pacific. He explained that further studies on the songs would allow them to better understand whale population dynamics in the area.
"Male fin whales in the Pacific sing just two very low notes, which are produced in different rhythms to create song," Helble explained. He added that the previous theory was that fin whales only sang a single song, distinct to a group or region. Their new study, however, shows that these are more complex than previously thought.
Recording Songs Underwater
Researchers were able to record a total of five song patterns. While some were unique for that specific area, other songs were found to be similar to those recorded in the past - found in whale populations from the northwest coast of the United States. Dr. Guazzo explains that when a new song is recorded at a location, scientists often interpret this as a sign of migration, with the song carried by the new whale as an individual or as an entire population.
To additionally confirm whether the whales found in Kauai are from a single population or whether they came from different populations, converging on the same spot, additional studies are required. The local Hawaiian population needs to be monitored - visually identifying them, conducting genetic analysis, or even the use of long-duration tags - and determine where else these fin whales go after Kauai.
Most whale songs, such as those of the fin whale, are low-frequency and are inaudible to the human ear. These recordings are typically modulated, or sped-up, to allow researchers to listen and study them.
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