Why Sri Lanka is a haven for blue whales
The biggest creature ever to live abounds on Sri Lanka’s porches. The elusive blue whale, twice the weight of the hugest known dinosaur, seems to like Serendib just as much as you and I do. The boon for science is comparably enormous, not to mention tourism.
It’s hard to resist listing some superlatives. Thirty meters long. Up to 200 tons in weight. Her heart the size of a Suzuki four-door, her arteries wide enough for children to crawl through. Her vocalizations are louder than a screaming jet engine. She can gulp down 9000 pounds a day and her surfacing spout could sprinkle the roof of a four-story building if it happened to be alongside.
Despite this glaring ginormousness, blues are rare to see. A scant few thousand remain on the planet and they range in deep seas, far from human traffic. We know precious little about them, their fascination notwithstanding. Sri Lanka may be poised to change all that, however. This past decade has established Lanka as one of the world’s premier locales for seeing blues and for studying them. Marine biology and the economy both stand to gain.
Working different sides of the street, two Sri Lanka-rooted afficianados have spearheaded ‘discovery’ of our offshore blues in the past decade. U.K. amateur naturalist Gehan de Silva Wijeyaratne has done yeoman’s labor documenting, explaining and publicizing main concentrations of blues. Describing himself as a ‘connector’ linking science with commercial opportunity, he has helped brand Sri Lanka as a blue whale ecotourism destination. With her Sri Lanka Blue Whale Project, marine scientist Asha de Vos has pioneered sophisticated methods of mapping and predicting whale concentrations, beyond reliance on sheer observation. She is also implementing a photo census of local blues and working to ameliorate whale strikes by megaships that kill and maim.
While applauding tourist opportunities to view blues, de Vos and de Silva Wijeyaratne both fear disruption and damage to whales from excessive and aggressive tour boat practices. De Silva Wijeyaratne comments on the need for regulation and training for whale-watching outfitters: “In 2008, I launched the international branding of Sri Lanka as ‘Best for Blue Whale’,” he comments. “But I am anxious that Sri Lankan whale-watching conform to ‘best practices’: boats should not chase or disrupt feeding and socializing whales.” He stresses that sound practices benefit tourists as well as whales: “Keeping a distance may prolong encounter times, draw curious whales toward boats, and leave them comfortable enough for interesting social behavior. Regulation and continuous training in responsible whale watching is very important for the welfare of whales and viewers alike.”
Rumors of blues in Lankan waters have long circulated among fishing folk and local naturalists. It took sustained inquiry, however, to separate facts from fancy for a picture of the true phenomenon out there. Sperm whales, for example, are big enough to be misidentified as blues by untrained observers. It is now unmistakably clear, however, that Sri Lanka is one of the best places in the world to see blue whales.
Why is this little island such a great place to view blues? Beneath shallow waters outward from Sri Lankan shores lies continental shelf: a gently sloping sea floor stretching to an edge where the bottom drops steeply into the deep. Blues here and elsewhere seldom spend much time on continental shelf, perhaps because their main food is scant there, perhaps also because it is too cramped there for maneuvering away from their main predator: orcas or killer whales. Blues do, however, enjoy cruising deeper waters at shelf edges. They may find lots to eat there and they may use the shelf edges in navigating. When a shelf is dozens or hundreds of miles wide, blues cannot easily be seen or studied even if they’re out there on the edge. Whale-watching excursions would require overnighting on boats. Sri Lanka, however, sits in the southernmost wedge of the Indian (sub)continental shelf, which just happens to ‘pinch in’ close to shore at three points, Mirissa and Trincomalee among them. This brings blue cruising lanes within range for whale-watching day trips and sometimes within sight of observers on shore, a true rarity in the world. At Trincomalee, moreover, a deep sea canyon cuts across the shelf right into the harbor, bringing blues even closer. (The third ‘pinch’ point, Kalpitya, has not so far turned out great for spotting blues, but does seem to be a hot venue for sperm whales).
Blues feed almost exclusively on krill, thumbnail-size crustaceans which swarm in huge orange clouds anywhere from the surface to a couple of hundred meters down. Blues swallow krill by the gazillion in massive mouthfuls. Feasting on such tiny creatures may, paradoxically, be part of the reason blues grow so huge, but that must be a story for another day. Krill feed on microscopic plants (phytoplankton) or on microscopic animals (zooplankton) which graze in turn on phytoplankton. The richest krill blooms arise in chilly northern and southern waters where phytoplankton and zooplankton thrive best because cold seas hold more nutrients—needed for phytoplankton photosynthesis–than tropical seas: another counterintuitive fact to explain some other day.
Sri Lanka sits in tropical seas of course, so if blues are finding krill here, something quite unusual might be happening. One explanation could be a tropically-rare abundance of nutrients in Lankan waters, due to its steep topography and monsoon rainfall. Some one hundred rivers and streams flush from Sri Lanka’s land surface into its surrounding ocean. Nutrients gush downward and outward, as if a mashed potato scoop were shedding organic gravy into a tasty offshore mush. Teensy plants synthesize the fertile slurry with sunlight so that krill can eat their fill and blues dine in style. Well, maybe: we really don’t know yet how much krill is out there.
De Vos thinks a substantial portion of Lankan blues may be residential year-round, not migratory like other blues, and therefore quite special. If she’s right, a nutrient soup supporting substantial krill blooms might be the reason. De Silva Wijeyeratne thinks that nutrient flow has something to do with blue abundance here, but gives more play to the theory that Lankan blues are mainly migratory like those elsewhere. The two theories need not contradict: it could be that some Lankan blues are migratory, some are residential, and some switch from one to the other depending on circumstance. Migratory Lankan blues would be special in their own way. Atlantic and Pacific blues migrate north and south. Northern blues catch the cold water krill blooms at high latitudes in springtime, then turn for warm equatorial waters where they breed and give birth. Southern blues do exactly the same but in the opposite direction on an opposite seasonal calendar whereby it is autumn (austral spring) when the warming sun brings krill blooms around Antarctica.
Anyway, as de Silva Wijeyeratne theorizes, migratory Lankan blues, if that is indeed what they are, would be special in a different way because they oscillate east and west, not north and south. They shun cold water. They pass Dondra Head going east into the Bay of Bengal in December/January and west into the Arabian Sea in March/April. Why, you ask? What is the biggest ‘seasonal’ event in the Indian Ocean region? Come on, you know this one. Yes, that’s right, of course. But what does that have to do with blue whale migration? Unfortunately, that too—you guessed it—is a story for another day.
(From the archives of Echelon Magazine)