Marine Biologists Think That Blue Whale Song Times Indiciate Specific Seasons

For years, wildlife experts have been fascinated by the singing of blue whales. New research led by Stanford researchers suggests that whales tend to change their singing times before they migrating south.

The study was just published in the Cell journal Current Biology. Previous observations have shown that male blue whales typically sing at night during the summer. However, they were observed to sing during the daytime before they migrate south for the breeding season.

Blue whales (Balaenoptera musculus) are the largest species on Earth. According to National Geographic, there used to be approximately 300,000 blue whales before they were hunted in the 1990s. By 1966, blue whale hunting was banned.

Now, there are around 10,000 blue whales left and are listed in the Endangered Species Act. Today's threats to the endangered species include illegal hunting, pollution, habitat loss, and entanglement in fishing gear.

Whale Song Recordings

Understanding their migratory behavior can help protect endangered blue whales. Keeping track of the species include tagging whales, such as National Geographic's Crittercam, and underwater microphones.

The team was able to tag 15 blue whales, which recorded their behavior between 2017 and 2019. The instruments have recorded nearly 4,000 songs.

Blue whale's songs are 188 decibels loud. However, some songs cannot be heard by humans due to the low frequency at 20 hertz.

Singing times seem to be associated with the feeding and mating cycle each year, explained biological oceanographer William Oestreich. During the summer, blue whales can be found the North Pacific hunting krill before the mating season in the winter months.

For years, Oestreich and his team have observed underwater sounds recorded by a microphone in Monterey Bay, California. After five years of observations, they noticed the pattern of nighttime songs associated with summer and fall, and daytime songs right before wintertime.

Nearly two terabytes of audio are recorded by the microphone in California per month. Recordings also revealed that the whales sing about 10 songs per hour during the night and around three songs every hour during the day.

Associating Songs with Seasons

Although experts believe that whale songs are associated with mating, there's still not enough evidence to explain why they sing or what causes their vocalizations to change. Marine Ecologist Jenny Allen from the University of Queensland said that there's still very little biological relevance for male blue whales to sing frequently at night during feeding season than singing more songs in the day before migrating.

However, marine biologist Ana Širović from Texas A&M University believes that switching song times indicate the migration season. The whales that her team tagged in Southern California show the opposite behavior of singing more daytime songs during the feeding season.

"Given that these songs travel hundreds of kilometers in the ocean environment, this might be possible, which could allow individual whales to make better-informed decisions on when to migrate," said Oestreich. In conclusion, the authors wrote that "real-time detection of this behavioral signal can also inform dynamic management efforts to mitigate anthropogenic threats to this endangered population."

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