Into the Great Wide Open: Dolphins and Whales of the Bay of Bengal

From the mottled blue bow of our research vessel, the MV Dhanyashree, I look out to the placid waters of Visakhapatnam harbour. An assortment of brightly coloured fishing boats line the berthing bay — fitting together almost hull-to-hull — their gear neatly packed and stowed on deck. Just beneath the surface, Bengal sergeants (Abudefduf bengalensis), a species of damselfish, dart between the algae-strewn pillars of our mooring berth, nibbling hesitantly at the unappetising green carpet. There is a sense of calm here that is uncharacteristic of a fish-landing site — alluding to the rapidly approaching moratorium on mechanised fishing, observed annually between April and June.

Originally a trawler, remodelled as a charter survey vessel, the MV Dhanyashree is equipped with all the worldly comforts one can hope for when out at sea. Now catering to the requirements of research teams — from oceanographers to meteorologists — it dons an air-conditioned cabin with six single bunks, outdoor seating in the form of a bolted-down sofa, and a freshly painted bathroom that stands out in stark contrast to the rest of its sun-beaten visage.

I am part of a team from WWF India, along with wildlife biologist and turtle whisperer Muralidharan M, fisheries scientists Dhaval Jungi and Honey Seles, and ornithologist Nikhil John. We will spend the next week traversing the coastline of Andhra Pradesh — a journey of over 900 kilometres — to document the cetaceans that utilise its pelagic waters (open seas). Cetaceans are a group of mammals that include dolphins and whales, and they remain woefully understudied in India, with limited open-source information pertaining to their abundance and distribution patterns, especially from the Bay of Bengal. This paucity of information persists despite the fact that the Indian Ocean region supports some of the highest levels of cetacean diversity on the planet. Numerous records of oceanic dolphins from spinners (Stenella longirostris) — famed dancers of the deep — to killer whales (Orcinus orca) — the largest of the “blackfish” — exist from this seascape. Similarly, species of rorquals, a family of “great whales,” including blue whales (Balaenoptera musculus), Bryde’s whales (Balaenoptera brydei) and the recently described Omura’s (Balaenoptera omurai), are also reported from the bay, through sightings as well as stranding events.

With the harbour master paid his dues and the last of our supplies loaded onto the vessel, we are ready to set sail. The excitement onboard is palpable as the 280-horsepower Sinotruck engine sputters to life. Through the deafening din, I cannot help but wonder what secrets the world’s largest bay has in store for us.

The surge picks up as we leave the coastline, fortified by sudden onshore winds. The vessel — which not so long ago bobbed therapeutically — now lurches forward, rising and dipping dramatically as we painstakingly make our way through incoming waves. “Don’t worry,” bellows Venky, one of the seven vastly travelled, former fishermen that comprise our crew. “It will get calmer once we’re further away from shore.” Apart from Dhaval, who hails from Gujarat’s Kharwa fishing community, none of us have spent extended periods onboard a fishing boat, let alone set foot in pelagic waters. Venky’s words of comfort do little to bolster morale, lost to the wind somewhere between the metallic groaning of the hull and the reverberations of an overworked engine.

The next morning, we wake up to far more favourable conditions. I stumble out of the cabin, exchanging incoherent pleasantries with Byraswamy, who has captained through the night shift, to an immense blue, the likes of which I have never seen. “Is this a sea state of 1, or what?” muses a beaming Murali, referring to the Beaufort wind scale for near-perfect conditions at sea. He is not wrong. The water stands still, painted a deep hue of blue and dotted only with the occasional ripple that makes its way across the surface.

After a cup of tea, we begin to prepare our equipment — binoculars, a GPS, datasheets, laminated species checklists, cameras armed with telephoto lenses and sun protection gear — for the day’s monitoring. The survey methods we are to follow are adapted from the “Eastern Canadian Seabirds at Sea (ECSAS) standardised protocol” and involve two observers and two spotters, standing at the bow, with each observer-spotter team covering a 90-degree arc on either side of the vessel. Both teams are to scan the horizon and record any cetaceans observed on their respective sides as we continue along a pre-determined route at a fixed speed of approximately eight nautical miles an hour. By employing a distance sampling framework, which involves recording the distance and angle at which an animal or group of animals is first seen, we are able to estimate species abundances, an important metric when attempting to identify hotspots or changes in populations through time.

In addition to cetaceans, our methods also allow for the systematic recording of other animals of interest, which in our case includes pelagic birds, i.e., birds that spend a large portion of their lives crossing oceans, making their way to land only to nest, and sea turtles.

 

Hours pass before we see our first cetaceans. “Look! I see fins at 70 degrees, 150 metres portside,” Nikhil shouts out as he wields his binoculars with a sense of assurance that only an ornithologist possesses. The rest of us frantically adjust our focus dials till we see the tall, falcate dorsal fins of Risso’s dolphins (Grampus griseus) slicing through the water’s surface. This pod of 6-8 individuals seems to show little interest in our vessel or us as they maintain their distance and continue to surge powerfully forward.

The sun, now directly overhead, beats down vengefully. We make our way off the bow at noon in search of pockets of shade. We are to continue at 3 pm. After lunch, most of us find spots to settle down and get some shut-eye. I wake up to commotion on deck, the sound of heavy footfall as the team and crew aggregate towards the vessel’s starboard side. Amidst the excited chatter, I decipher the much-anticipated words “pilot whales!” Less than 25 metres from us, a pod of short-finned pilot whales (Globicephala macrorhynchus) keeps pace, breaching with their prominent foreheads, their eyes only just clearing the surface. 

It isn’t until our third day at sea that we encounter Stenellas, a genus of dolphins that includes some of the more recognisable faces from the cetacean world. Stenellas are popularly known for their acrobatic manoeuvres, both above and below the surface. Less known perhaps for being extremely social, they are often seen interacting with pods of other dolphins and forming mixed-species pods.

Late one evening, as we approach a fishing vessel, we notice two toothed whales behaving peculiarly — not really breaching, not really diving, and not really lying motionless either. These animals seemed to glide along before spouting synchronously and dropping out of view. A sense of lacklustre accompanied their disappearance, unlike anything we’d come to expect from the many cetaceans we had encountered. We’d later learn that the pygmy sperm whale (Kogia breviceps) has earned the name the “floating whale” in Japan for this very behaviour. Another species we had fleeting interactions with was bottlenose dolphins (Tursiops sp.). Despite being reported relatively frequently from the bay, we only encountered two pairs during the expedition, one of which seemed to be quite at home amongst a pod of short-finned pilot whales. 

During our week at sea, we recorded over 500 cetaceans across 6 species, 8 species of pelagic birds, and around 50 olive ridley sea turtles. Despite being a pilot survey, it provided preliminary insight into the diversity of cetaceans utilising the waters of the Bay of Bengal. We formally documented the seasonality of breeding for some species, including spinner dolphins, Risso’s and pilot whales, and important inter-species interactions, shedding light on lesser-known aspects of their behaviour and ecology.

“As this expedition is a testament to, Andhra Pradesh’s offshore waters are home to spectacular species of whales, dolphins, whale sharks and turtles. However, when compared to some more accessible habitats, pelagic waters have historically been overlooked, and it is my hope that this work can help build a foundation for the periodic monitoring of these incredible spaces,” says Dr. Shanti Priya Pandey, Additional Principal Chief Conservator of Forest (Wildlife), Andhra Pradesh.

Much of what is currently known about oceanic cetaceans in India is from stranding records, where disoriented, injured, or dead animals wash ashore. While an invaluable database, this only paints a partial picture. The routine at-sea monitoring of populations is essential for us to begin to understand through a temporal lens the diversity, distribution patterns, and habitat use of cetaceans in the country’s Exclusive Economic Zone (EEZ). Given that marine mammal research is still in a nascent stage, it is crucial to establish collaborations between agencies, fishing communities, and the shipping industry to work at the scale required to address these gaps in our knowledge regarding some of the oceans’ most charismatic yet understudied species — eventually contributing towards their protection in these vast seas.

This survey was undertaken by WWF India’s Marine Conservation Programme, with support from Greenko Foundation and the Andhra Pradesh Forest Department.