Songs of survival: scientists confirm blue whales frequent Seychelles

Bryde’s, sei and sperm whales, some of the least-known species of beaked whales, and Risso’s, common bottlenose and striped dolphins. The tropical waters of Seychelles are rich in life and, as new research is confirming, a hotspot for whales and dolphins. ‘Aerial surveys from previous studies have shown that Seychelles has one of the highest levels of cetacean diversity and abundance in the south-western Indian Ocean,’ explains Dr Jeremy Kiszka, a biology professor at Florida International University (FIU) and a research associate at the Island Biodiversity and Conservation Centre at the University of Seychelles. Jeremy is also a Save Our Seas Foundation (SOSF) project leader investigating the importance of Seychelles for whales and dolphins. Working with a team of researchers, he has recently recorded 23 species in just two field seasons. ‘In Seychelles we have seen some of the world’s least-known species,’ he says. ‘Animals such as the Longman’s beaked whale have been seen alive only a handful of times, but they’ve been observed in large groups in Seychelles. We’ve also sighted a species off D’Arros that we’ve previously known only from the Southern Ocean, where it prefers cold, temperate and sub-polar waters.’

But there is one gargantuan visitor that looms a little larger in significance and mystery. The team of scientists from the University of Seychelles, FIU and Oregon State University, together with Oceanic Films, have confirmed that blue whales frequent Seychelles, especially between December and April.

‘Never in this life of mine would I have imagined that the biggest animal on planet earth soars in our oceans here in Seychelles!’ Dillys Pouponeau is a research assistant at the Save Our Seas Foundation D’Arros Research Centre (SOSF-DRC) and is deeply invested in the blue future of her home country. ‘This is just a few kilometres away from us and we had no idea. To me, this was big and exciting news and so precious because it represents the productivity of our oceans.’ She joined the expedition as a digital imaging technician with Oceanic Films who were filming ‘Blue Whales – Return of the Giants’ with funding from the National Science Foundation and HHMI Tangled Bank Studios. ‘I was first involved with the blue whales on the expedition up north to try and discover them,’ she explains. ‘I was part of the film crew, the team that would communicate the discovery and the science to the world through a film. Although I was a DIT [digital imaging technician], meaning my role was to manage the cards, download and store the footage in appropriate locations for post-production, I also assisted the cameramen and shot behind-the-scenes images.’

Jeremy is equally buoyant about the discovery. ‘It is remarkable to know that the largest animal on earth swims here,’ he marvels. Together with the team, he has co-authored ‘Acoustic detections and sightings of blue whales Balaenoptera musculus in the Seychelles, western tropical Indian Ocean (2020−2022)’, which was published in the journal Endangered Species Research on 9 November 2023. The confirmation is significant because Seychelles was a major hunting ground for Soviet whalers in the 20th century. As a new member of the International Whaling Commission in 1978, the Republic of Seychelles successfully lobbied to protect the Indian Ocean from whaling. And today, there have been five confirmed sightings over the course of five years. ‘It shows how regulations and legislations have indeed helped to prevent whaling and protect this species,’ says Dillys. ‘It also shows how nature can recover by itself and often all we need to do is leave it to do so. I wish that the people who worked on [the whaling ban] could see the fruits of their work. I wish they knew that we, “the future generation” at that time, got to see blue whales from a different perspective, and that we are proud of the work they did.’

‘Blue whales are protected because they are no longer legally, actively hunted, but they still face a range of threats,’ continues Jeremy. ‘Shipping traffic causes noise pollution and can lead to collisions. Climate change is altering the distribution and abundance of their key food, krill.’ There have been records that confirm blue whales in Seychelles since the 1960s. But there has been no previous single, dedicated effort to understand where and when these whales move, nor quantify how many there might be. In an exciting opportunistic sighting before Jeremy and the team began their work, two blue whales were recorded by scientists from the Save Our Seas Foundation D’Arros Research Centre (SOSF-DRC) close to D’Arros Island in 2016. Rare and elusive as blue whales are by nature, it’s a challenge to untangle their lives.

What the scientists can now confirm is that, of the four subspecies we know exist, it appears that it’s the pygmy blue whale that prefers to visit Seychelles. And it is the songs of the Sri Lankan acoustic group that were recorded on hydrophones (underwater microphones) deployed in Seychelles’ waters. ‘We now need to increase our research efforts to assess the abundance of these blue whales and why they are using Seychelles’ waters,’ says Jeremy. Some critical questions include: what do they do in Seychelles from December to April? How many are there? What do they eat and how could climate change impact their persistence in Seychelles? ‘We hope that this publication will help us motivate for more research on these animals and involve more local scientists to use this formidable opportunity to understand more about blue whales in tropical waters.’

The findings, Dillys says, will certainly also have implications for the research and monitoring work done by the team at the SOSF-DRC. ‘The Amirantes Islands, of which D’Arros Island is a part, is known to have hosted blue whales – and suffered atrocious whaling events. We can’t wait to understand their population status around D’Arros. Have they returned? How many are there? It will undoubtedly add value for our marine protected area. The coolest thing is that our work here involves studying not only the smallest animals alive, zooplankton, but also the biggest, blue whales.’

The first documented sighting of a blue whale at D'Arros Island, and it happened to be just a few metres in front of the D'Arros Research Centre. Photo by Justin Blake | © Save Our Seas Foundation

Further research is necessary not only because blue whales – and many species that are part of this incredible cetacean diversity – are of conservation concern, but also because they form part of the wider ecosystem. ‘We know that cetaceans are important predators in the sense that, as mammals, they need to eat a lot of food and so they rely on stable and productive environments that can sustain them. We also know that they are capable of impacting community and ecosystem dynamics through important processes such as nutrient cycling,’ says Jeremy. ‘When whales and dolphins feed at depth and then come to the surface to defecate and urinate, they pump huge, bio-available nutrient into the system for primary producers (such as phytoplankton). Tropical waters are generally nutrient poor. These blue whales – and all the cetacean diversity recorded in Seychelles – could be important because they may fuel the ecosystem.’

For Jeremy, the wonder of the rich ocean around Seychelles is only beginning to reveal its magic. There is much left to do, and he hopes that this latest publication will help them to achieve several aims.

An important feather(star) in Seychelles’ ocean conservation cap, the findings herald valuable opportunities and responsibilities for an emerging generation of scientists and conservationists in Seychelles. ‘I really hope that we can share this with more students from Seychelles and from further afield. We already have in our team two talented students from Seychelles who are involved in this research and I would like them to take leading roles in this project.’

For Dillys, the opportunities strike a deep chord. ‘Since I am also a scientist, I was involved in everything happening on the expedition’s boat. Here on D’Arros, the research involves surveying in the boat and deploying hydrophones. This gives me, as an emerging scientist, hope. It also gives me a new sense of stewardship and I feel the responsibility of preventing such events [as whaling] from happening again for the next generation.’

Jeremy is optimistic as he concludes, ‘These blue whales have no borders, so we need to conduct research at the appropriate scale. We’d need to collaborate internationally, with partners in countries like Sri Lanka, if these whales migrate across the ocean. It’s a phenomenal opportunity to understand these blue whales and raise awareness about them.’