Dugong Gone?

by

Mark Hager©2015

What’s become of our local ‘mermaids’?

In the past few years, naturalist Gehan de Silva Wijeyeratne and hotel chains have cleverly promoted the ‘big five’ Lankan animal attractions, echoing the African tourism big five of lion, leopard, African elephant, rhino and buffalo. For Sri Lanka, the idea is that a two-week tour stands a decent chance for sightings of blue whale, sperm whale, Asian elephant, leopard and sloth bear. It’s an inspired marketing ploy, though it’s too soon to judge its success in augmenting wildlife tourism. Many factors are at play of course.

It’s kind of fun to play with the idea of ‘five more’: fascinating animals that a Sri Lankan tour could yield in addition to the ‘big five.’ What should we put on that list? We’ve got mugger (freshwater) and saltwater crocodiles, sublime apex predators both, to start with. How about water monitors, a personal favorite, close cousin of those flamboyant Komodo dragons? There’s a Youtube video of male monitors in a Lankan river fighting for mating privileges just like their charismatic Komodo kin on Animal Planet. Should we spotlight giant squirrels, excellent example of evolution’s ‘island effect,’ whereby small species grow large in the absence of bigger competitors? And how about primates: purple langurs (‘leaf eater monkeys’), grey langurs, toque macaques and big-eyed night-going lorises found only here and in India? It seems like at least one of five sea turtle species should get consideration, no? And did you know that fishing cats hunt by night in our suburban wetlands? We haven’t even touched on snakes, lesser whales and dolphins, or crazy birds both domestic and migratory. Honorable mention could go to ‘ugaduwa’ (civet cat), nocturnal freak, which once fell from a high roof to land right beside me as I sat in our garden with my evening reading, then scrambled up some vines to disappear after we stared each other down for a Moment. What the hell was that!? (Obsessed for days, I finally I identified it from the web.)

But there’s a girl who’d rival the top five just by showing up: demure dugong, shy damsel of the shallow seas. One morning, house full of extended family, I got a video up on my computer: no intent to divert the conversational buzz. But quickly: ‘What is that?’came the cries. Aquatic pig, nuzzling truffles from sea bed? What’s front, what’s rear? Is that thing real? She’s very real but unfortunately also very rare in Lankan waters these days, though she used to cavort in large numbers along the northwest coast from Jaffna to Kalpitiya. Where has she (and he, of course) gone and why?

Dugongs represent the last surviving species in a once-flourishing extended family. She is now the planet’s sole exclusively saltwater mammalian herbivore. Her closest cousins, three remaining species of manatee, spend all or part of their time in fresh water. Dugongs and

manatees together belong to the order Sirenia, so designated because ancient sightings of them may lie behind myths of sea sirens or mermaids—part woman, part fish—that entrance and bewitch sailors. The Malay word ‘duyong’ means ‘mermaid.’ Dugongs have a knack for perching upright on their tail fins in shallow water, clasping their nursing pups to their pectoral breasts with their forearm flippers.

Amazingly enough, dugongs and manatees together are today’s closest living relatives to elephants. Many dugongs even have tusks. From a pig-size common ancestor some 50-60 million years ago, elephant forebears evolved their distinctive trunks while sea sirens took up and perfected their aquatic lifestyles. Dugongs are thereby closer to elephants than to other marine mammals like whales, dolphins, seals and walruses, who took to the waves during the same era by way of ancestors in common with today’s hippos. This great mammalian ocean craze came on the heels of the meteor and climate change cataclysm that wiped out dinosaurs and their proliferating aquatic kin 65 million years ago. Mammals jumped in to exploit biological space vacated by vanishing marine reptiles.

Three meters long and half a ton in weight when full-grown, dugongs feed almost exclusively on seagrass found in calm, shallow seawater and in brackish estuaries and lagoons or in coastal bays and mangrove environments. They can hold their breath no more than three minutes. In brief dives from the surface, they snuffle through seagrass beds, using their prehensile snouts—physiologically analogous to elephant trunks—to yank up spears of grass and their especially nutritious roots. As adults, they swallow down some 30 kilograms a day.

We know precious little because dugongs are surprisingly hard to study. They frequent waters that tend to be turbid. Eons of predation by sharks, killer whales and crocodiles have made them timid by nature. They die easily in captivity due to difficulty in providing exactly the right breed of seagrass. Semi-nomadic, dugongs need to move regularly from overgrazed seagrass beds to ones offering more to eat. They have exceptional hearing and communicate among themselves with chirps, whistles, barks and trills. They engage each other in affectionate nuzzling, including fin-to-fin and nose-to-nose caresses. Calves bond closely with mothers, frequently riding on their backs.

As recently as a few decades back, numbering in many millions, dugongs occupied a quasi-contiguous range covering littoral zones throughout the greater Indian Ocean and appendages like the South China Sea, Red Sea and Persian Gulf, comprising perhaps forty countries from Mozambique in the west to Australia and nearby Pacific islands in the east. In recent decades, numbers appear to have declined drastically, with dugongs now absent in extensive portions of their former range and increasingly confined to semi-isolated pockets. They are considered extinct in nearby Maldives. There may be fewer than 100 left in Lankan waters. Once reported in swarms of hundreds, they are now generally spotted only one at a time and rarely. Though pitiful by former standards, the Gulf of Mannar population may be the largest remaining in South Asia.

One cause of dugong decline is heavy hunting. Their meat is prized by those familiar, their fat can be rendered into clean-burning oil and their tough hides can be put to many uses. Easily accessible in shallow water, they typically do not move especially quickly as they munch systematically through seagrass beds. In earlier times they would often have done so in companionable close-knit clusters, easy for rapid mass killing. Fishing, even with traditional techniques, can also decimate dugong numbers. Unable to surface when snared in nets, they quickly drown.

Perhaps the main ongoing threat to dugong survival lies in habitat destruction. Seagrass beds she depends on require particular conditions of light, sea floor composition and water chemistry. Assault on this requisite balance comes from many sides. Though dugongs have long been classified a protected species, protection of their habitat is a vast challenge. Sea-floor trawl fishing and dredging both damage seagrass beds directly and increase water turbidity detrimental to growth. Sewage, herbicide runoff from farms and heavy metals from mines pollute coastal waters. Mangrove clearance and landfill for construction poach on grazing ranges. An estimated 7% of dugong habitat disappears every year. That’s half of her remaining habitat lost every decade. If that trend continues, she cannot long survive outside highly protected and managed enclaves, if at all.

Aside from these distressingly routine habitat insults, Lankan dugongs may have sustained a singular blow from the 2004 tsunami. Studies indicate that the 2011 tsunami in Japan destroyed up to 70% of seagrass coverage in areas it struck. Could something comparable have happened in Sri Lanka? The northwest shores south of Jaffna down to Puttulam escaped with fairly light life and property loss as tsunami waves dissipated their energy in shallow seas. But salvation for people and homes may have been disaster for dugong habitat as the demonic waves churned themselves out against shallow sea floor. Seiches (large waves bouncing shoreline to shoreline) reportedly reverberated through Palk Strait and the Gulf of Mannar on Boxing Day. Shredded grass beds, greatly increased turbidity and mangled mangrove stands would have been probable consequences, along with leaching of sediment and microbes into the sea as waves receded from the land. If the tsunami bludgeoned dugong habitat, it might mean either good news or bad. The good news might be that habitat will slowly recover from the one-off cataclysm and that dugong numbers will recover accordingly. The bad news might be that the tsunami dealt a death blow to habitat and that we will soon see (or more likely not see) the last of our local dugong.

More bad new lies in the slow dugong reproductive cycle. She gives birth only once in five years or so and only to single calves. On behalf of the United Nations Environment Project, Dr. Donna Kwan currently directs the ‘Dugong, Seagrass and Coastal Communities Initiative’ in Sri Lanka, coordinating with the Department of Wildlife Conservation, the International Union for Conservation of Nature and Dilmah Conservation. The Initiative aims to preserve and restore habitat by nudging coastal communities toward benign fishing practices and by engaging them in dugong and seagrass stewardship. (As fish and shrimp nurseries, seagrass beds support

sustainable yields for fisheries livelihoods.) In exchange for such service, the Initiative supports improved and diversified livelihoods for participating families. If successful, the Initiative could provide a pilot for similar efforts elsewhere. Otherwise, we may be witnessing the saddest Lankan wildlife story of all.

A graduate of Harvard Law School, Mark Hager lives in Pelawatte with his family. In addition to his inquiries on political economy and Sri Lankan wildlife, he consults on complex legal and technical writing challenges. mark.hager@gmail.com