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Spitting Dolphins of the Mekong River

Text and photography by Roland Seitre


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Irrawady Dolphins
Irrawady dolphins, Orcaella brevirostris, were discovered in the main river of Burma. They are widepsread over SE Asia, along the coasts in the sea but enter estuaries and rivers. In the lower Mekong river is a relict population of an endemic sub- species isolated for more than 10000 years. Totally cut for the sea, they used to live down to Phnom Pen, the capital, and the huge Tonle Sap lake, but now the hundred or so individuals are restricted upstream to the Laos border Image #: 065698

Dry season drained all waters from the Mekong Basin. However, the great river, fed by the everlasting snows of the Tibetan highlands, still flows in an endless ribbon of silver reflection, but otherwise muddy waters. A thousand kilometres upstream from the Delta, the water surface shakes for an instant, before a large spatter breaks it. A small fish flew into the air. Just behind appears the real cause of all this disturbance : a greyish dolphin with a round head. Finally, I have found the rare Mekong river dolphin, a survivor, and even witnessed its strange, and poorly known, unique hunting technique.

Strung Tren is a town which seems to have grown during the colonial days. The charm of large avenues and a wide esplanade overlooking the river just looks like some I have seen in Madagascar or western Africa. Early morning, canoes with their outboard engines are everywhere, taking people up to Laos or down to mainland Cambodia, if not up some subsidiaries. It is easier, faster and safer along the mine safe waterways than on the dirt tracks. A fisherman, former hunter in his own words, will take me around to look for the elusive marine mammal that inhabited, until recently, the waters around this remote town of the north of the country.

Many rivers across the globe are home to dolphins, generally these are primitive with very long nose in shape of a bill, and often blind. Such animals occur in the Indus, the Ganges, the Yangtze, the Amazon, the Orinoco and the Parana river systems, each species confined to one system. But in some case, new, modern sea dolphins have colonised their riverine habitat, with some success. Such is the case of the Irrawaddy dolphin, named after the Burmese river where he was first found. By all criteria, this grey dolphin is not restricted to the Irrawaddy : it lives all along the coasts of south-east Asia from India to Borneo and Australia, and goes into many rivers quite upstream to reach lakes inland Borneo for example. In the Mekong river, it gets to the level of the first waterfalls, on the Laos-Cambodia border. But what happened within the Mekong and the lake Tonle Sap is that in this area, heart of Cambodia, isolation and natural selection led to specialisation. The sea dwelling animals became a purely (and isolated) population. Although they look similar, they are genetically (and obviously ecologically) different. They are adapted to this fresh water system and do not mix with the delta populations of the Irrawaddy dolphin.

Our boat floats downstream, the pilot negotiating with ease the rapids where rocks seem to break the surface. During this time, the traffic of goods is suspended: large boats cannot plight the river. Come next rainy season they will. When water level will raise five to ten metres! But now is the time of the fishing. Fish is the major protein source for the Cambodians. Chased from all small watercourses by the dry, they congregate in the big river itself and particularly in the few deep water pools: when the river is only inches deep, some pools reach 15, 20 metres! So with the fish, you find the dolphins! Just have to ask the fishermen where the best spots are!

It is a faint blow, that you will hear more than see, a very short exhibition of a grey back with a rounded fin. Within less than a second, all vanished in the dirty waters. Wait a few more seconds to get other brief visions, other glimpses. Altogether, one on the right, a female with calf on the left, two behind the boat. Nothing spectacular ! But the river is no Marineland and the dolphins here live their life at their pace, without bothering about the people around. At this point, their life is earned by fishing ! We quickly follow but obviously they are aware of our presence and easily avoid us. Nevertheless, they do not flee. I quickly realise they stay in the same area of the river, the size of a football field, whereas the wideness of the Mekong, one kilometre here , should allow them to go anywhere. It is clear : they are showing us their real habitat of the dry times : the few rock pools they can only survive in because this is the only place where they can feed. Come the wet, they could be anywhere.

Around us, fishermen tackle with nets, eperviers, traps, their targets. Of the dolphin art of fishing we see nothing, except, occasionally, these sprays seemingly useless, that appear far in front, before the animal surfaces to breathe. Scientific literature mentions the specific behaviour without any explanation. Is it a game ? No other dolphin is known to do it in nature. And these seem far too busy to be playing... I witnessed tens of sprays, but only once did I see that small fish, a few centimetres long, fly with the drops. Could the dolphin be capable of spitting water meters away and use this talent to upset the swim of its prey, and then catch it with ease ?

Belugas, the large white dolphins of the Arctic, share the spitting capabilities : in aquatic parks that keep either species, it has been used to fancy the public. Add a three meter long water spray to a jumping show and one has a very popular attraction ! Cambodian fishermen like their dolphin. Traditionally they respect them. Occasionally they kill them in their gillnets. Unintentionally but with the small size of the population, always a problem for the future of the species. Vietnamese soldiers used to shoot them for practice, food and even to use their oil in diesel engines... Nowadays less than a hundred survive and it has become a small tourist attraction to visit them in the centre of the range. Dams are planned upstream between Laos and Thailand, that could diminish water supplies in the dry, threaten even more the dolphins…but also the fish and the fishermen. Dolphins are really an indicator of the health of the river!

* As captioned the images are of Mekong when in the wild and Thailand when captive. Physically identical and belonging to the same species. Precise spitting behaviour could only be shot in captivity as it is naturally only performed underwater, although there is one picture as described in text from the surface.