One hot 2019 afternoon in Lakshadweep, as marine mammal scientist Divya Panicker sat engrossed in listening to recordings retrieved from underwater sound recorders, she came across low blue whale moans, amid a cacophony of a rooster crow.
Panicker described the acoustic experience with the giants as “one of the most thrilling parts” of her study — the first to document blue whale songs in Indian waters in the Lakshadweep archipelago in the Arabian Sea.
She speculates that there were at least two blue whales singing at a time. “The song is made up of three notes and ranges between 30 and 100Hz. I sped up the songs several times to bring them within my hearing. It was quite wacky listening to low blue whale moans with a rooster crowing in the background,” Panicker reminisced.
Analysis of recordings from late 2018 to early 2020 revealed that blue whales were present in Lakshadweep waters during April and May, just before the southwest monsoon season.
“Although we know blue whales occur and are singing in these waters, we do not know if they are travelling through or feeding in these waters. One of the next steps is to carry out dedicated visual surveys in April and May over the next few years to understand their behaviour and some prey sampling during this period,” Panicker, a doctoral student in oceanography at the University of Washington, told Mongabay-India.
Because blue whales track productive waters, their presence in Lakshadweep, which is on the cusp of major tourism and infrastructure expansion, demonstrates that the waters in this archipelago are rich and productive.
“The reef, lagoon, island and open ocean are intricately linked and any development and infrastructure plans for the islands need to be carried out within the ecological limits of this fragile ecosystem. It is important to understand their ecology and distributions to draw up a science-based species-specific conservation or management strategy,” adds Panicker.
Marine mammal expert Dipani Sutaria, who studies humpback whales in the Indian waters, said blue whale songs, belted out by males possibly for finding a mate, likely signal that the area is a breeding ground for whales during certain parts of the year.
“All cetaceans (whales, dolphins, and porpoises) use sound to forage (find food), navigate and communicate. Sound travels a little over four times faster in seawater than it does in air, and in the absence of light, cetaceans have evolved perfectly to use sound as a way of seeing. Cetaceans are highly social and baleen whales such as blue whales and humpback whales produce different kinds of vocalisations, some of which can travel thousands of kilometres,” Sutaria said.
“They make high-frequency sounds for locating prey and the other kind of vocalisation is a song; or a repetition of units. Only the males sing in both blues and humpbacks and are considered to be related to mate selection and increasing the opportunity to find mates, a sign of the breeding season.
“So if you have singing whales in an area at a certain time of the year, it means this area is likely a seasonal breeding ground,” Sutaria told Mongabay-India.
Sutaria’s team found a blue whale singing off the Kerala coast in the Arabian Sea in May 2021. “Our team is trying to explore the presence of humpback whales off the southwest coast of India using passive acoustic monitoring, and in May 2021 we found a blue whale singing (including some foraging calls) from the same ‘acoustic’ population in the Arabian Sea.
“Our finding fits in with the Lakshadweep observation that blue whales were present/move through the southwestern waters during April and May,’ Sutaria, member of the IUCN Cetacean Specialist Group, added.
Melodies in the Indian Ocean
Blue whales (Balaenoptera musculus spp.), are an endangered species globally. While Antarctic blue whales (B. m. intermedia), reach up to 30 meters in length and weigh 200 tonnes (approximately 33 elephants), populations of smaller pygmy blue whales, growing up to about 24 metres and weighing roughly half of Antarctic blue whales, are known to occur in the Indian Ocean, the smallest of the major oceans on Earth, but the fastest-warming tropical ocean.
Pygmy blue whales (PBW) are found throughout the Indian Ocean, including the northern Indian Ocean (NIO) and the Arabian Sea.
Blue whale vocalisations offer clues to scientists about the identities of these mammals. Based on their distinct song types, scientists say four possible populations of pygmy blue whales, comprising one or two subspecies to date (B. m. brevicauda andB. m. indica), occur in the Indian Ocean.
The so-called “acoustic populations” of pygmy blue whales (PBW) in the Indian Ocean include the NIO PBW (sometimes referred to as ‘Sri Lanka song’, likely B. m. indica); northwest Indian Ocean; southwest Indian Ocean (sometimes referred to as ‘Australia song’); and southeast Indian Ocean PBW populations (sometimes referred to as ‘Madagascar song’).
The songs recorded in the Lakshadweep waters, says Panicker, were similar to those recorded by Abigail Alling in Sri Lanka in 1980, currently called the northern Indian Ocean blue whale song. These songs have also been heard off the Chagos archipelago (southern end of the mid-oceanic Laccadive-Maldivian-Chagos ridge).
“Usually, blue whales (Balaenoptera musculus spp.), have very consistent song patterns but interestingly in some of our recordings, they were dropping the last unit. This has not been reported for this song type and for future work it would be cool to understand why they may be doing this,” she shared.
The study extends the known range of this song type (northern Indian Ocean blue whale song) a further 1,000 kilometres (620 miles) northwest of Sri Lanka and is particularly significant because Indian waters are a habitat for blue whales but there is very little dedicated research on these animals.
The Lakshadweep research was carried out by the University of Washington in collaboration with the Wildlife Programme at the National Centre for Biological Sciences. On-field dive support was provided by Lakshadweep Scuba Adventures (Anwer Hussein, Syed AbdullaKoya, Amanullah VP, Abdul Raheem PP).
Acoustic recorders were deployed by divers on the reef flats near the underwater slope. Over 13 months, recorders were retrieved and redeployed every three months or so – retrieving the data, changing batteries, and analysing low-frequency bands to look for blue whale vocalisations.
Panicker elaborates that blue whales consume dense patches of prey to grow to these large sizes. “They feed on some of the smallest animals in the ocean – zooplankton and shrimp – which are prey to a whole host of pelagic fishes and mammals. Therefore, studying blue whale distributions gives a glimpse into the most productive and rich habitats in the Arabian Sea that are heavily influenced by monsoonal cycles and a changing climate.”
According to the latest report by the IPCC, the surface of the Indian Ocean has warmed faster than the global average. Globally, anthropogenic warming is very likely to further decrease ocean oxygen concentrations and this deoxygenation is projected to persist for thousands of years, the report warned.
Commercial whaling had nearly wiped out blue whale populations globally in the 20th century and they are only now slowly recovering from these impacts. They are long-lived animals, having one calf at a time with long gestation periods. “The populations in the Arabian Sea were persecuted by whaling ships in the 60s and 70s as well. Some other threats whales face in this densely populated region are ship strikes and a changing climate,” explained Panicker.
For instance, an important blue whale feeding area near Sri Lanka is right next to a major global shipping lane. Deep-sea exploration and mining plans will generate constant noise across vast areas and can also impact blue whale populations.
“We also know from recent studies that there are changes in the monsoon patterns and an intensification of the frequency and duration of cyclones – this is likely to have major impacts on blue whale prey and in turn will affect whales as well,” she said. Usually calmer than the Bay of Bengal, researchers caution the Arabian Sea is getting more active with the rapid intensification of cyclones due to climate change; cyclone Okchi and Tauktae were the most recent ones.
Resolving ambiguities to conserve cetaceans
Sutaria points out that despite centrally-sponsored conservation plans and regulations that cover blue whales in the Indian waters, ambiguity on issues needs to be addressed for science-based conservation of cetaceans.
“There is ambiguity on issues such as habitat protection; mechanisms to mitigate mortality from sound pollution, habitat loss and entanglements. Also, marine tourism such as dolphin watching needs to follow national guidelines; protocols should also be included in the Wildlife Protection Act, 1972.”
“At the moment marine wildlife tourism is open to overexploitation and habitat loss. Would dolphin tourism, for example, come under the ambit of the Wildlife Protection Act (WPA), or the commerce or tourism ministry,” Sutaria asked, adding that the WPA, 1972 also needs to be updated, along with the species lists under the schedules. All marine mammals are Schedule 1 species under the Act, receiving the highest protection.
She underscored the importance of more research to bridge the knowledge gap on cetaceans in India to effectively inform conservation efforts and policy. “The importance of detailed ecological research to inform conservation, and to increase opportunities for researchers to bridge the knowledge gap is vital in India.
“One area that can be of immediate use is setting up marine stranding networks and studying these strandings from biological and conservation contexts, to better understand the species biology, their life at sea and if possible the cause of death.”
“There are protocols to follow in the case of dead animals (handling the carcass) and live animals. You can find out if an animal has got caught in a certain kind of fishing gear or if it has died naturally. There could be reasons such as anthropogenic causes (underwater noise), disease outbreaks or climate-related factors,” said Sutaria who co-manages the scientific content of marinemammals.in, a cetacean sighting and stranding database that covers 1016 records from 1748 till the present.
For example, in Lakshadweep’s remote islands with limited connectivity, consistent help from local fishermen, divers, the government administration and the people of Lakshadweep helped Divya Panicker in setting up her study. She believes that putting recorders and listening for whales in several areas across the Indian waters would reveal a lot more information on not just blue whales but also other whale species such as humpback and Bryde’s whales.
Regional cooperation is key, especially to study and conserve marine mammal populations that range across different countries, says Panicker. The Arabian Sea Whale network and the marine mammal network of India are examples of such cooperative networks.
But countries like India are under intense pressure to extend protected area networks to meet biodiversity protection goals such as the proposal by global policymakers to extend protections to at least 30 per cent of terrestrial, marine and freshwater ecosystems around the world.
The ambition to scale up coverage and effectiveness of protected and conserved areas is expected to play a key role in discussions in the post-2020 global biodiversity framework due to be agreed upon at the UN Biodiversity Conference (CBD COP15) in Kunming, China, in May 2022. (Mongabay India)