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Deep Sea Serenades May Be from Unknown Blue Whale Species

Could a new subspecies of blue whale have been discovered in the Indian Ocean?

A recent study published in the journal Endangered Species Research, has discovered what scientists believe to be a new blue whale song from Southern Madagascar to the central depths of the Indian Ocean.

Beneath the waves of the Indian Ocean is a biodiversity ballad. Choirs of snaps from fishes, clicks and crackles from clams and corals, harmonies of hums and whistles add to the unique sounds of the sea. Adding baritone voices to this seascape symphony, are the enthralling, majestic tones of the great whale song.

The loudest songs originate from the largest whale species, the blue whale. The species can weigh up to 380,000 pounds and grow to 100ft long. These gentle giants can be found swimming in oceans all around the globe. They produce low-pitch, recognizable songs which are unique within different families. The blue whale songs are actually louder than the sound of a jet engine, achieving 188 decibels, compared to a jet engine’s 140 decibels. Blue whales are the deep divers of the ocean, and so their elusive behavior and mysterious music sparks the curiosity and imagination of many scientists and civilians alike. These magnificent mammals have only recently risen to fame through their voices.

The New Acoustic Crescendo

A recent 2020 study published in the journal Endangered Species Research, has discovered what scientists believe to be a new blue whale song from Southern Madagascar to the central depths of the Indian Ocean.

Dr Salvatore Cerchio originally heard the song several years ago in 2017. Dr. Cerchio is the Director of the African Aquatic Conservation Fund's Cetacean Program in Massachusetts and the lead author of the study. Whilst the study primarily focused on Omura’s whales off the Madagascan coast, Dr. Cerchio and his colleagues recorded the unfamiliar blue whale serenades. The team decided to move their hydrophone instruments deeper into the water to hear more.

Dr. Cerchio suggests “if you put a hydrophone somewhere no one has put a hydrophone before, you’re going to discover something”.

During data analysis of the acoustic recordings, the team recognized the same song. It became clear that they had potentially found a mysterious blue whale population. Using acoustic data to identify a new population is an indirect and less intrusive approach. However, acoustic data collection still provides accurate results, like dusting for fingerprints at a crime scene.

In 2018, the Scientific Committee of the International Whaling Commission (IWC) was evaluating the status of Indian Ocean blue whale families when Dr. Crechio’s team reported their new and exciting discovery. The findings raised new questions about the populations and structure of blue whales in the Indian Ocean.

At this time, a team from the University of New South Wales (NSW) in Australia were also performing blue whale studies in the Indian Ocean. Emmanuelle Leroy, a member of the University of NSW team, recognized that the new song was the same as one they had recorded near the Chagos Archipelago in the central Indian Ocean.

Data was analyzed from three sites. It suggests the blue whale community may spend the majority of their time in the Arabian Sea, the west of the Chagos and in the North western region of the Indian Ocean.

Screen Shot 2021 04 12 at 2.34.00 PMAn image of the globe showing the locations where the whale song was recorded. The red line represents the potential route new subspecies of blue whales travel.

This is an interesting development. Previously, researchers presumed that blue whales inhabiting the Arabian Sea and near Sri Lanka were from the same population. The songs may highlight the need for greater research on how expanding maritime industrial activities are affecting marine mammals in the region. The next step for confirming the new subspecies is genetic samples, but blue whales have an elusive nature beneath the deep-depths and away from shores. Sample collection often involves the use of darts fired from a crossbow or veterinary rifle. This makes sample collection very challenging as it requires close proximity to the whale and may cause the whale unnecessary stress.

There is still very little understanding of the function of blue whale songs, although researchers believe that they are used to help attract mates. This means that if the songs change, two populations will be unable to communicate and, therefore, will not mate with one another. This causes the populations to become divided. Eventually leading to populations evolving into subspecies, with different behaviors and characteristics. Effectively, it is like changing native languages in humans, where new communities are formed with different cultures that align to speakers of that language.

Currently, there is no evidence to suggest this population has completely stopped communicating with other blue whale populations. There is also a need to gather information on what may have caused this population to separate from the other communities. The important next steps in this research would be to gain a greater understanding of this mysterious population, such as their interactions with other populations in the northern Indian Ocean and their conservation status.

Blue Background

In a time before whaling, it was estimated that numbers of blue whales were booming at around 250,000. However, due to human activity and hunting, sadly blue whales are now one of the rarest species in the ocean. These gentle, beautiful giants were hunted for their body and blubber to the brink of extinction. The 20th century was a devastating period for blue whales. There are now only 10,000 to 25,000 blue whales remaining worldwide. The populations have only just started recovering at an incredibly slow rate in the last few decades after the suspension and banning of commercial whaling.

This abhorrent activity across the decades nearly eliminated the already small and vulnerable global populations of humpbacks, blue, fin and sperm whales. Today, two countries still commercially hunt whales. A year after the Scientific Committee of the International Whaling Commission (IWC) put a ban on commercial whaling, Japan engaged in “scientific whaling” in 1987. Iceland followed suit in 2003, with their commercial hunts resuming in 2006. Commercial hunts have resulted in the discovery and destruction of rare hybrid species. For example, in 2018, a fin-blue whale was accidentally killed – something which is difficult to come to terms with for many marine biologists and conservation experts.

Importance of the Blue Whale Song

Blue whales are a key role in the marine food chain and have a significant part in maintaining ocean health. They are able to produce a rich source of nutrients for numerous marine animals and sustain populations of krill that they, in turn, rely on for food.

By studying the majestic music of these mammals, scientists can predict population numbers, growth, and specific family movements. Although family members sing the same song, each individual has their own tone. It is like yourself and a friend singing the same song. This allows scientists to predict how many members a particular family unit may have.

Through research, scientists have found five distinct subspecies of blue whales. They include:

  • Antarctic blue whales (Balaenoptera musculus intermedia),
  • North Atlantic and North Pacific (Balaenoptera musculus musculus),
  • Pygmy blue whales (Balaenoptera musculus brevicauda),
  • North Indian Ocean (Balaenoptera musculus indica),
  • South Pacific Ocean (Balaenoptera musculus unnamed species) blue whales).

These subspecies may be growing and diversifying further, as highlighted by Dr. Cerchio and his team in their 2020 study.

Acoustic Collection during Covid-19

While Covid-19 has caused great harm to many, it has actually afforded a much-needed reprieve to our planet and many of its species. In the initial months of the global lockdown, following the outbreak of Covid-19, there was a significant slowdown in worldwide shipping. During this period, the oceans possibly reached their quietest levels in over a century with regards to human noise. Scientists have assembled around 130 underwater hydrophone stations. These will be used to document what the ocean may have sounded like before the Industrial Revolution. This may lead to recording sounds from more species for the first time as they are not being drowned out by anthropogenic (human-made) noise.

The unusual effects the Covid-19 pandemic has had on the marine environment and animals have given the world hope about the recovery from the destructive degradation that humans have driven over recent decades. A discovery like this shows there are independent populations and communities that are still significantly unknown. These populations will have individual adaptations and contrasting requirements, which will need further study for scientists to determine and understand. In order to conserve these gentle giants and other marine species, there needs to be vast protection measures put into place to ensure the needs of all species are accounted for. However, for now, this mysterious community of blue whales will continue to spark curiosity as they harmonize with the rest of the marine ensemble beneath the ocean waves.

By Ella Farrelly

Research paper source:

Cerchio, S., Willson, A., Leroy, E., Muirhead, C., Harthi, S. A., Baldwin, R., Cholewiak, D., Collins,T., Minton, G., Rasoloarijao,T., Rogers, T., & Willson, M. (2020). A new blue whale song-type described for the Arabian Sea and Western Indian Ocean. Endangered Species Research, 43(2), 495-502.

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