Species News

Moving even further east, we stay on the continent and hear from Dr Dove and her work on the remaining population of Irrawaddy dolphins in the Mekong River ... as you'll read the news isn't positive and urgent action is needed to save these remarkable animals. (You can also learn more by visiting Dr Dove's FaceBook page "Help save the Mekong Irrawaddy dolphins from Extinction")

The Mekong River Irrawaddy dolphin (Orcaella brevirostris) population inhabits a 190km stretch of the Mekong River between Cambodia and Lao PDR. This population has been listed as critically endangered on the IUCN Red List of Threatened Species since 2004.
Since mortality monitoring commenced in 2003, the dolphin population has suffered 93 deaths of which over 60 percent were calves under two weeks old. Research carried out by Dr Verné Dove over the past 3 and a half years has found that the dolphins have high levels of environmental contaminants (DDT, PCBs, & Mercury) in their system, which has depleted their immune system, rendering them defenseless against disease. In addition a disease agent known as Aeromonas hydrophila has been identified as the main cause of death in several of the neonatal dolphins and older dolphins. These findings are significant as the latest population abundance monitoring surveys, reveal that there are only approximately between 64 and 76 Irrawaddy dolphins remaining in the Mekong River, with this figure declining each year with an annual average mortality of 13 dolphins. This is a drastic decline in numbers, as only 30 years ago locals report seeing thousands of dolphins.

Dr Verné Dove a veterinarian from Australia with a strong marine mammal background, and a Masters in Conservation Medicine, joined WWF-Cambodia as a volunteer in 2006. She volunteered for 3 years before being given a consultancy position in late 2009.
Her main research focus has been determining the high cause of mortality in the Irrawaddy dolphins, particularly in neonatal calves. In addition to undertaking necropsies on all the dead dolphins, she has also done research on population monitoring including abundance, movement and
distribution; behaviour assessment; looking at the effect of eco-tourism; water quality monitoring; toxicology and acoustic work.



In September 2008 Dr Dove completed a Master’s Thesis dissertation which summarised all her scientific findings. These findings were made public in a report issued by WWF-Cambodia in June 2009. She revealed that pollution in the Mekong River has pushed the local population of Irrawaddy dolphins to the brink of extinction. Her hypothesis was that environmental chemicals found in high levels in dolphin samples, for example DDT, PCBs and Mercury have all acted synergistically to reduce the immune systems capability of warding off disease. She also hypothesised that limited genetic diversity due to inbreeding was possibly another factor contributing to the dolphin deaths, as inbreeding depression can further reduce the immune’s systems ability to function effectively. Aeromonas hydrophila and several other opportunistic bacterial disease that were identified as contributing to the cause of some dolphin deaths would not normally be fatal unless the dolphin’s immune systems were suppressed.



The source of some of the environmental contaminants may involve several countries through which the Mekong River flows as these pollutants particularly the pesticides are widely distributed in the environment. However some contaminants such as Mercury, may be from local gold mining activities in Cambodia. These findings are worrisome as the same pollutants may also pose a health risk to human populations living along the Mekong that consume the same fish as the dolphins.

The Mekong River dolphins are isolated from other members of their species and unless a recovery project is undertaken to reduce the very high and unsustainable mortality level, this population will become functionally extinct in the not too distant future. There is still a small window of opportunity to save this population, but time is running out.

Some further reading for you ...

http://www.divshare.com/folder/547250-3de to download:
• The dolphin necropsy report in Khmer and English
• Broadcast quality footage of the dolphins swimming the Mekong River at Cambodia.

http://www.panda.org/wwf_news/multimedia/photo/irrawaddy_dolphin.cfm to download:
• High quality photos of the dolphins playing in the Mekong River in Cambodia.

Moving a little further east, to Myanmar and Bangladesh, we now hear from another very good friend of WDCS, Brian D. Smith (Director, Asian Freshwater and Coastal Cetacean Program, Wildlife Conservation Society). Brian has been working on Irrawaddy dolphins for many years now and is as close to an authority on this species as we're going to get!

Freshwater dolphins are among the most threatened wildlife on earth and WDCS has been at the forefront of efforts to conserve these enigmatic animals. The rivers, brackish lagoons and estuaries where these dolphins live are generally subject to a much greater impact from human activities compared to marine environments. This poses a particular challenge for efforts to conserve them which is further magnified by the fact that the range of these animals is limited to emerging nations where human needs are enormous, financial support is minimal, and local expertise is still in the early stages of development. One species of grave conservation concern is the Irrawaddy dolphin Orcaella brevirostris, which is considered by the IUCN to be “vulnerable” with five geographically isolated populations that are “critically endangered.” Despite the apparent gloomy outlook, Irrawaddy dolphins have been the topic of some recent good news, thanks to the collaborative efforts of WDCS and the Wildlife Conservation Society (WCS).

In 2002, WDCS and WCS initiated a study on the distribution, abundance, and factors threatening the population of Irrawaddy dolphins in the Ayeyarwady River of Myanmar. This study indicated that the population is restricted to about 400 km of channel length in the far upstream reaches of the river and that it numbers only about 60-70 individuals. It also found that the population was under immediate threat of extinction from electrocution and prey depletion due to the illegal use of electricity to catch fish. An additional study was carried out on a cooperative fishery practiced between the dolphins and cast-net fishermen where the animals voluntarily herd schools of fish toward the fishing boats and awaiting nets. Based on the results of these studies, in December 2005 the Department of Fisheries (DoF), Myanmar, established a protected area for the dolphins and cooperative cast-net fishermen in a 74-km river segment just upstream of the city of Mandalay. Since establishing the protected area an ambitious conservation program has been conducted that includes components to significantly reduce or eliminate electric fishing, promote the sustainability of the human-dolphin cooperative cast-net fishery, protect aquatic habitat and sustainable fisheries, develop a core dolphin conservation team, and monitor the status of dolphins. Frequent patrols in the protected area indicate that electric fishing has been dramatically reduced and a range-wide survey of the population in January 2010 suggests that the number of animals has stabilized or it may have even increased. Although the program is currently run by WCS and the DoF, this conservation success would not have been possible without the early, pro-active support of WDCS.



Although the major emphasis of WDCS’s work with Irrawaddy dolphins has been on populations that are at immediate risk of extinction, not only in the Ayeyarwady River but also in Songkla Lake (Thailand), Chilika Lagoon (India), the Mahakam River, (Indonesia), and the Mekong River (Cambodia and Lao PDR), it has also collaborated with WCS on a study in Bangladesh that discovered the world’s largest population of the species by more than an order of magnitude. Using rigorous scientific techniques, local and international scientists estimated that nearly 6,000 Irrawaddy dolphins live in freshwater regions of Bangladesh’s Sundarbans mangrove forest and adjacent waters of the Bay of Bengal. Despite the good news, the same study found that the dolphins are increasingly threatened by accidental entanglement in fishing nets, declining freshwater supplies, caused by upstream water diversion in India, and sea-level rise due to global climate change. The Ganges River dolphin, Platanista gangetica, an “endangered” species with a range that overlaps with Irrawaddy dolphins in the Sundarbans mangrove forest, faces similar conservation threats. Efforts are currently underway to establish a protected area network in “hotspot” channel segments of the Sundarbans where both species occur in particularly high densities.



Urgent conservation attention is needed to arrest declines in the populations of all freshwater dolphin species, and the recent likely extinction of the Yangtze River dolphin or baiji is a potent reminder of the dire cost of inaction. However, the lesson of WDCS-supported work in Myanmar and Bangladesh is that we can make a difference and that there still remains a great deal of hope for the future of freshwater dolphins.

Below we hear from a good friend of WDCS, Dr Dipani Sutaria and her work on Irrawaddy dolphins in Chilika lagoon in India - enjoy!

The best days are when the water is calm and soft with a few ripples reflecting colours that come out to touch you. Sometimes, the softness is disrupted by a clown-like marine creature spitting a long spout of water almost at you – I first saw this creature in 2002 and till today, Irrawaddy dolphins simply amuse me. Their presence gives our study site a character far different from any place I have visited, as long as one has the patience to wait, experience and laugh!

Chilika lagoon is a beautiful brackish water lagoon along the southern coast of Orissa, India. When we speak to fishers living along Chilika shores, they tell us with a smile that Irrawaddy dolphins have been present in Chilika, ever since it was formed. Called ‘khera’ in the local language, the local populace considers these dolphins to be a blessing and a sign of fish presence. The late jejebapa (grandfather) of Naran babu, at the time a full ninety nine years old, told me “ Daughter, the day there are no dolphins in Chilika, there will be no fish, it is just not possible”. I used to keep a day in the week free from scientific inquiry and on that day, I would go across to the rajhans channel, and traverse the waters in a dug-out canoe with a young fisherboy. He used to call out to the dolphins “Kuu ku ku ku ku”…the dolphins would smoothly glide along with our canoe. This deep, knowing and almost spiritual connection that the fisher people of Chilika have with their dolphins is the most hopeful and beautiful part of ongoing conservation research here.

Memories of the first time I visited the field site on Holiday with Ranjeet Pattnaik in March 2002 are still vivid. We got our first record of A1 or scoopfin – one of our most coveted individual’s (and may she live long and pass her survival genes to many generations that follow). When the project started in 2004, with conservation objectives we needed to estimate population size, area of occurrence, home ranges and patterns in space use using boat surveys to put together a photo-ID catalogue of the dolphins. The first few weeks were depressing as we were not getting as many new fins as we wished, but slowly and steadily our catalogue grew and I still remember the joy every time we found a new dramatically shaped fin . I had to decide then if we should give them alpha numerical ID’s or actual nicknames and I chose the former much to my assistant’s discontent! In field there is a certain joy in not doing what everyone expects you would do…. we must allow ourselves some pleasures in a place where there is no dance, wine or chocolate and the electricity cut constantly challenges our sanity.

We managed to identify 80 individual dolphins using natural marks, one more beautiful than the next (pictures). The younger animals are difficult to identify as their fins have still not got tarnished and dashed. We used these data to estimate abundance of the population which is approximately 109 to112 individuals at CV=0.07 based on surveys from November 2004 to December 2006. We also found that the total Extent of Occurrence for Irrawaddy dolphins in Chilika was <330km2; and the Area of Occupancy was <131km2, both of which are less than half of the available habitat. The dolphins concentrate their use in two core areas in the Lagoon: the Outer Channel (12km2 ) and the South-Central Sector (49km2). The core areas appear to be the major feeding grounds for Irrawaddy dolphins in Chilika Lagoon, with feeding, milling and socializing dominating the day time activity budget. Interestingly, the site fidelity of individual dolphins is high with more than 80% of the individuals remaining within 10km of their mean centre. Some of the individuals showed large ranges, and we call them explorers while others stay within their small home ranges, and we call them stayers. We have shown below some of the individuals and their home ranges, to give you an idea of the space used.

These dolphins are striking in their habits. They exhibit various kinds of feeding strategies, solitarily and in groups of two - three to large groups of eight-nine animals. Feeding strategies include plume feeding, kerplunking, herding fish to shallow waters and then feeding sideways along the shores. The dolphins are also seen feeding from fixed shrimp and fish trap nets, which are used as barriers for dolphins to catch fish from. Another special kind of strategy used by Irrawaddy dolphins is that of ‘spitting’ We have observed that the spitting action is used to stun fish either from the bottom or from within the water column.



Long term behavioral studies in Chilika is a dream which I hope comes true. I now observe social behavior between individuals to assess the society and associations that exist between individuals. One of my recent exciting observations was that of herding behavior, which is common during the months of March to May, the probably breeding season for Irrawaddy dolphins in Chilika! Our work is greatly limited by not having access to genetic samples and thus not knowing the sex of the individuals we are observing. I hope that future work in Chilika is able to overcome such barriers.

The dolphins do not use the entire lagoon, which brings us to one of the major concerns-that of habitat quality and restoration. Shrinking of the lagoon has been a constant worry and the Chilika Development Authority uses maintenance dredging to maintain the lagoon ecosystem-they even opened a new mouth to the sea to maintain sea water flow.

As we await research news from our researchers in India, enjoy this short story from a child who lives alongside the population of Irrawaddy dolphins in Chilika Lagoon, India

This article was written on June 26th, 2008 by Vaibhav Pirpa, from class 6 of Stokes Memorial School, Shimla.

Life in Chilika Lake, Orissa (as written by Vaibhav, the Irrawaddy dolphin)

I am a dolphin. I live in Chilika lake, Orissa. People call me an IRRAWADDY DOLPHIN. I am very different from other dolphins. I don’t have any snout. I like to eat many fishes. Some birds are bad and snatch food from me. I have sonar by which I communicate to my relatives. My nose (blowhole) is above my head. This happened because of evolution. I am a helper to man. I take many shoals of fish to the net and they get trapped. They (fishermen) give me food in return. But I have seen that some fishermen that catch fish sometimes catch us and we die. Some people drive motor boats. We come near them and the propeller cuts us. When I swim, I see many eels near me. I have a dorsal fin on my back. My tail looks like a whale’s tail. I got my name “Irrawaddy dolphin” when I was found in the Irrawaddy river. I like to do many things such as somersaults and spitting. I sometimes get fungal infections from which I get patches on my skin. Our population is decreasing. Please help us and don’t kill us. We get very hurt.

Irrawaddy dolphins were recently split into two species. The 'true' Irrawaddy, O. brevirostris is known to occur in five freshwater systems and the nearshore marine waters of Southeast Asia extending as far west as the east coast of India, while the newly described snubfin dolphin, O. heinsohni occurs in the coastal waters of northern Australia and southern Papua New Guinea. Over the next couple of weeks, we'll hear from researchers working on both species so technically this should be called the "Genus of the month" but it makes sense to do it this way, so stick with me!

But before we get started with the "notes from the field", here's a quick overview of the Irrawaddy dolphin - with the extracts taken/borrowed mostly from the "Irrawaddy Action Plan - Status and Conservation of Freshwater populations of Irrawaddy dolphins" by Brian Smith et al, produced as a result of a workshop that WDCS co-funded in 2005 - no point in reinventing the wheel and Brian tells us how it is so perfectly!

(And if anyone would like a copy of the report then please just ask!)

Freshwater populations occur in three river systems - the Ayeyarwady (formerly Irrawaddy, where the dolphin gets its name from of course) in Myanmar (formerly Burma), the Mahakam in Indonesian Borneo, and the Mekong in Laos, Cambodia and Vietnam; and two partially isolated brackish or freshwater lakes – Chilika Lagoon in India and Songkhla Lake in Thailand. There is (or was) also a sub-population in the Malampaya Sound in the Philippines however little is known about their current status. However they, and the Ayeyarwady, Mahakam, Mekong and Songkhla populations are classified as “critically endangered” on the IUCN Red List. According to IUCN criteria, there's not enough information available to assess the Chilika Lake population, however, it is considered likely to be endangered due to it's low population size and high mortality rate. (NH says - More dolphins are dying than are being born into the population and if things continue at this rate perhaps by the time sufficient information is available for a listing, it'll be joining the other freshwater populations as being designated "critically endangered").

All five freshwater populations are believed to be demographically isolated from members of the species occurring in marine waters. The downstream range extents of the riverine populations are about 180, 500 and 1000 km from the sea in the Mahakam, Mekong and Ayeyarwady rivers, respectively, and, with a single exception of a carcass recovered near the mouth of Chilika Lake (which may have drifted through its opening during low tide), no strandings or sightings of Irrawaddy dolphins have been documented along adjacent coastlines within 80 km of both Chilika and Songkhla lakes.



The freshwater populations also represent a fairly unique adaptation within the Order of Cetacea as members of a species that is found in both nearshore marine and riverine/marine appended lake environments. They share this attribute with only two other cetaceans: the finless porpoise, Neophocaena phocaenoides in the Yangtze River of China and the tucuxi, Sotalia fluviatilis in the Amazon and Orinoco rivers of South America.

Less is known about the marine populations of Irrawaddy dolphins however a significantly larger population of at least a few thousand animals occurs in the inner and outer Sundarbans Delta of Bangladesh. Interestingly, Irrawaddy dolphins do not occur in fluvial waters of the Ganges-Brahmaputra-Meghna river system upstream of the Sundarbans Delta, possibly due to inter-specific competition from Ganges River dolphins Platanista gangetica, which are true freshwater specialists.



Other marine populations are known from the coastal waters of Thailand, Sumatra and Malaysian Borneo and we'll be hearing more about them in the coming weeks too!

May is going to be Irrawaddy overload - with hopefully some exciting news towards the end of the month ... but for the moment i'll leave you to consider these rather special and relatively small dolphins!