The Irrawaddy dolphin (''Orcaella brevirostris'') is a
euryhaline species of
oceanic dolphin
Oceanic dolphins or Delphinidae are a widely distributed family of dolphins that live in the sea. Close to forty extant species are recognised. They include several big species whose common names contain "whale" rather than "dolphin", such as the ...
found in scattered subpopulations near sea coasts and in estuaries and rivers in parts of the
Bay of Bengal
The Bay of Bengal is the northeastern part of the Indian Ocean, bounded on the west and northwest by India, on the north by Bangladesh, and on the east by Myanmar and the Andaman and Nicobar Islands of India. Its southern limit is a line betwee ...
and
Southeast Asia
Southeast Asia, also spelled South East Asia and South-East Asia, and also known as Southeastern Asia, South-eastern Asia or SEA, is the geographical south-eastern region of Asia, consisting of the regions that are situated south of mainlan ...
. It closely resembles the
Australian snubfin dolphin
The Australian snubfin dolphin (''Orcaella heinsohni'') is a dolphin found off the northern coasts of Australia. It closely resembles the Irrawaddy dolphin (of the same genus, ''Orcaella'') and was not described as a separate species until 2005 ...
(of the same genus, ''
Orcaella
The snubfin dolphins (''Orcaella'') are a genus of cetaceans containing two members: the Irrawaddy dolphin (''Orcaella brevirostris'') and the Australian snubfin dolphin (''Orcaella heinsohni''). The genus was long believed to be monotypic with ...
''), which was not described as a separate species until 2005. It has a slate blue to a slate gray color. Although found in much of the riverine and marine zones of South and Southeast Asia, the only concentrated lagoon populations are found in
Chilika Lake in
Odisha
Odisha (English: , ), formerly Orissa ( the official name until 2011), is an Indian state located in Eastern India. It is the 8th largest state by area, and the 11th largest by population. The state has the third largest population of ...
,
India
India, officially the Republic of India (Hindi: ), is a country in South Asia. It is the seventh-largest country by area, the second-most populous country, and the most populous democracy in the world. Bounded by the Indian Ocean on the so ...
and
Songkhla Lake
Songkhla Lake ( th, ทะเลสาบสงขลา, , ) is the largest natural lake in Thailand. It is on the Malay peninsula in the southern part of the country. Covering an area of 1,040 km2 it borders the provinces of Songkhla and Pha ...
in southern
Thailand
Thailand ( ), historically known as Siam () and officially the Kingdom of Thailand, is a country in Southeast Asia, located at the centre of the Indochinese Peninsula, spanning , with a population of almost 70 million. The country is b ...
.
Taxonomy
![OrcaellaBrevirostris](https://upload.wikimedia.org/wikipedia/commons/8/8b/OrcaellaBrevirostris.JPG)
One of the earliest recorded descriptions of the Irrawaddy dolphin was by
Sir Richard Owen
Sir Richard Owen (20 July 1804 – 18 December 1892) was an English biologist, comparative anatomist and paleontologist. Owen is generally considered to have been an outstanding naturalist with a remarkable gift for interpreting fossils.
Ow ...
in 1866 based on a specimen found in 1852, in the harbour of
Visakhapatnam
, image_alt =
, image_caption = From top, left to right: Visakhapatnam aerial view, Vizag seaport, Simhachalam Temple, Aerial view of Rushikonda Beach, Beach road, Novotel Visakhapatnam, INS Kursura submarine museu ...
on the east coast of India.
It is one of two species in its genus. It has sometimes been listed variously in a family containing just itself and in the
Monodontidae
The cetacean family Monodontidae comprises two living whale species, the narwhal and the beluga whale and at least four extinct species, known from the fossil record. Beluga and Narwhal are native to coastal regions and pack ice around the Arctic ...
and
Delphinapteridae. Widespread agreement now exists to list it in the family
Delphinidae
Oceanic dolphins or Delphinidae are a widely distributed family of dolphins that live in the sea. Close to forty extant species are recognised. They include several big species whose common names contain "whale" rather than "dolphin", such as the ...
.
Etymology and local names
The species name ''brevirostris'' comes from the
Latin
Latin (, or , ) is a classical language belonging to the Italic branch of the Indo-European languages. Latin was originally a dialect spoken in the lower Tiber area (then known as Latium) around present-day Rome, but through the power of the ...
meaning short-beaked. It is very closely related to the
Australian snubfin dolphin
The Australian snubfin dolphin (''Orcaella heinsohni'') is a dolphin found off the northern coasts of Australia. It closely resembles the Irrawaddy dolphin (of the same genus, ''Orcaella'') and was not described as a separate species until 2005 ...
(''Orcaella heinsohni''). The two snubfin dolphins were only recognised as separate species in 2005 when a genetic analysis showed that the population found along the coast of northern Australia forms a second species in the genus ''Orcaella''. The ''Orcaella'' dolphins are close relatives of the oceanic dolphins in
Globicephalinae
Globicephalinae is a subfamily of oceanic dolphins that includes the pilot whales (''Globicephala'' spp.), the pygmy killer whale (''Feresa attenuata''), the rough-toothed dolphin (''Steno bredanensis''), the false killer whale (''Pseudorca cra ...
subfamily.
Vernacular names for the Irrawaddy dolphin include:
* th, โลมาอิรวดี ''loma irawadi'', โลมาหัวบาตร ''loma hua bat'' ("alms-bowl dolphin", due to the shape of their heads)
*
Odia: ଶିଶୁମାର sisumāra, ଭୁଆସୁଣୀ ମାଛ ''bhuāsuṇi mācha'' (lit. oil-yielding dolphin), lagoon area local name- ଖେରା ''kherā''
*
Filipino
Filipino may refer to:
* Something from or related to the Philippines
** Filipino language, standardized variety of 'Tagalog', the national language and one of the official languages of the Philippines.
** Filipinos, people who are citizens of th ...
: ''lampasut''
*
Bengali
Bengali or Bengalee, or Bengalese may refer to:
*something of, from, or related to Bengal, a large region in South Asia
* Bengalis, an ethnic and linguistic group of the region
* Bengali language, the language they speak
** Bengali alphabet, the w ...
: শুশুক ''shushuko''
*
Indonesian
Indonesian is anything of, from, or related to Indonesia, an archipelagic country in Southeast Asia. It may refer to:
* Indonesians, citizens of Indonesia
** Native Indonesians, diverse groups of local inhabitants of the archipelago
** Indonesian ...
: ''pesut mahakam/ikan pesut''
*
Khmer: ផ្សោត ''ph’sout''
*
Lao: ປາຂ່າ ''pa’kha''
*
Malay
Malay may refer to:
Languages
* Malay language or Bahasa Melayu, a major Austronesian language spoken in Indonesia, Malaysia, Brunei and Singapore
** History of the Malay language, the Malay language from the 4th to the 14th century
** Indonesi ...
: ''empesut''
*
Burmese: ဧရာဝတီ လင်းပိုင် ''eyawadi lăbaing''
Description
![Orcaella brevirostris 1878](https://upload.wikimedia.org/wikipedia/commons/b/b8/Orcaella_brevirostris_1878.jpg)
The Irrawaddy dolphin's colour is grey to dark slate blue, paler underneath, without a distinctive pattern. The dorsal fin is small and rounded behind the middle of the back. The forehead is high and rounded; the beak is lacking. The front of its snout is blunt. The flippers are broad and rounded. The
finless porpoise
''Neophocaena'' is a genus of porpoise native to the Indian and Pacific oceans, as well as the freshwater habitats of the Yangtze River basin in China
China, officially the People's Republic of China (PRC), is a country in East Asia. ...
(''Neophocaena phocaenoides'') is similar and has no back fin; the
humpback dolphin (''Sousa chinensis'') is larger, and has a longer beak and a larger dorsal fin.
It ranges in weight from with a length of at full maturity.
Maximum recorded length is of a male in Thailand.
The Irrawaddy dolphin is similar to the
beluga The beluga whale (/bɪˈluːɡə/) (Delphinapterus leucas) is an Arctic and sub-Arctic cetacean. It is one of two members of the family Monodontidae, along with the narwhal, and the only member of the genus Delphinapterus. It is also known as the wh ...
in appearance, though most closely related to the
killer whale
The orca or killer whale (''Orcinus orca'') is a toothed whale belonging to the oceanic dolphin family, of which it is the largest member. It is the only extant species in the genus ''Orcinus'' and is recognizable by its black-and-white ...
. It has a large
melon
A melon is any of various plants of the family Cucurbitaceae with sweet, edible, and fleshy fruit. The word "melon" can refer to either the plant or specifically to the fruit. Botanically, a melon is a kind of berry, specifically a " pepo". Th ...
and a blunt, rounded head, and the beak is indistinct. Its
dorsal fin
A dorsal fin is a fin located on the back of most marine and freshwater vertebrates within various taxa of the animal kingdom. Many species of animals possessing dorsal fins are not particularly closely related to each other, though through c ...
, located about two-thirds posterior along the back, is short, blunt, and triangular.
Dorsal fin shapes differ from one Irrawaddy dolphin to another.
The flippers are long and broad.
These dolphins are usually two-toned, with the back and sides being gray to bluish-gray and the belly lighter.
Unlike any other dolphin, the Irrawaddy's U-shaped blowhole is on the left of the midline and opens towards the front of the dolphin.
Its short beak appears very different from those of other dolphins, and its mouth is known for having 12-19 peg-like teeth on each side of the jaws.
Behaviour
![DKoehl Irrawaddi Dolphin jumping](https://upload.wikimedia.org/wikipedia/commons/d/df/DKoehl_Irrawaddi_Dolphin_jumping.jpg)
Communication is carried out with clicks, creaks, and buzzes at a dominant frequency of about 60 kilohertz, which is thought to be used for
echolocation. Bony fish and fish eggs,
cephalopods, and
crustacean
Crustaceans (Crustacea, ) form a large, diverse arthropod taxon which includes such animals as decapods, seed shrimp, branchiopods, fish lice, krill, remipedes, isopods, barnacles, copepods, amphipods and mantis shrimp. The crustacean group can ...
s are taken as food. Observations of captive animals indicate food may be taken into the mouth by suction. Irrawaddy dolphins are capable of squirting streams of water that can reach up to ; this distinct behaviour has been known for herding fish into a general area for hunting. They do this sometimes while
spyhopping
Cetacean surfacing behaviour is a grouping of movement types that cetaceans make at the water's surface in addition to breathing. Cetaceans have developed and use surface behaviours for many functions such as display, feeding and communication. ...
and during feeding, apparently to expel water ingested during fish capture or possibly to herd fish. Some Irrawaddy dolphins kept in captivity have been trained to do spyhopping on command. The Irrawaddy dolphin is a slow swimmer, but swimming speeds of were reported when dolphins were being chased in a boat.
Irrawaddy dolphins are shy of boats, not known to bow-ride, and generally dive when alarmed. They are relatively slow moving but can sometimes be seen spyhopping and rolling to one side while waving a flipper and occasionally breaching. They are generally found in groups of 2-3 animals, though sometimes as many as 25 individuals have been known to congregate in deep pools. Groups of fewer than six individuals are most common, but sometimes up to 15 dolphins are seen together.
Traveling and staying in groups not only enables Irrawaddy dolphins to hunt, but it also creates and maintains social bonds and allows copulation to occur.
It surfaces in a rolling fashion and lifts its tail fluke clear of the water only for a deep dive. Deep dive times range from 30 to 150 seconds to 12 minutes. When 277 group dives were timed (time of disappearance of the last dolphin in the group to the emergence of the first dolphin in the group) in
Laos, mean duration was 115.3 seconds with a range of 19 seconds to 7.18 minutes.
Interspecific competition has been observed when Irrawaddy dolphins were forced inshore and excluded by more specialized dolphins. When captive humpback dolphins (''Sousa chinensis'') and Irrawaddy dolphins were held together, reportedly the Irrawaddy dolphins were frequently chased and confined to a small portion of the tank by the dominant humpbacks. In
Chilika Lake, local fishers say when Irrawaddy dolphins and
bottlenose dolphins
Bottlenose dolphins are aquatic mammals in the genus ''Tursiops.'' They are common, cosmopolitan members of the family Delphinidae, the family of oceanic dolphins. Molecular studies show the genus definitively contains two species: the comm ...
meet in the outer channel, the former get frightened and are forced to return toward the lake.
Mating
A female or male dolphin will attempt to pursue a mate for about a few minutes. They intertwine facing their bellies together and begin to copulate for 40 seconds. Once copulation has occurred, the dolphins will break away from each other and set off in different directions.
Reproduction
![Irrawaddy Dolphin Sundarban West Bengal August 2019](https://upload.wikimedia.org/wikipedia/commons/3/36/Irrawaddy_Dolphin_Sundarban_West_Bengal_August_2019.jpg)
These dolphins are thought to reach sexual maturity at seven to nine years. In the Northern Hemisphere, mating is reported from December to June. Its gestation period is 14 months; cows give birth to a single calf every two to three years. Length is about at birth. Birth weight is about . Weaning is after two years. Lifespan is about 30 years.
Feeding
There are plenty of food items that this dolphin feeds upon. They include fish, crustaceans, and cephalopods. During foraging periods, herds of about 7 dolphins will circle around prey and trap their victim. These prey entrapments occur slightly below the water surface level.
Habitat and subpopulations
![DSC 0764f](https://upload.wikimedia.org/wikipedia/commons/a/a8/DSC_0764f.jpg)
Although sometimes called the Irrawaddy river dolphin, it is not a true
river dolphin
River dolphins are a polyphyletic group of fully aquatic mammals that reside exclusively in freshwater or brackish water. They are an informal grouping of dolphins, which itself is a paraphyletic group within the infraorder Cetacea. Extant riv ...
, but an
oceanic dolphin
Oceanic dolphins or Delphinidae are a widely distributed family of dolphins that live in the sea. Close to forty extant species are recognised. They include several big species whose common names contain "whale" rather than "dolphin", such as the ...
that lives in
brackish water
Brackish water, sometimes termed brack water, is water occurring in a natural environment that has more salinity than freshwater, but not as much as seawater. It may result from mixing seawater (salt water) and fresh water together, as in estuari ...
near coasts, river mouths, and estuaries. It has established subpopulations in freshwater rivers, including the
Ganges
The Ganges ( ) (in India: Ganga ( ); in Bangladesh: Padma ( )). "The Ganges Basin, known in India as the Ganga and in Bangladesh as the Padma, is an international river to which India, Bangladesh, Nepal and China are the riparian states." is ...
and the
Mekong
The Mekong or Mekong River is a trans-boundary river in East Asia and Southeast Asia. It is the world's twelfth longest river and the third longest in Asia. Its estimated length is , and it drains an area of , discharging of water annual ...
, as well as the
Irrawaddy River from which it takes its name. Its range extends from the
Bay of Bengal
The Bay of Bengal is the northeastern part of the Indian Ocean, bounded on the west and northwest by India, on the north by Bangladesh, and on the east by Myanmar and the Andaman and Nicobar Islands of India. Its southern limit is a line betwee ...
to
New Guinea
New Guinea (; Hiri Motu: ''Niu Gini''; id, Papua, or , historically ) is the world's second-largest island with an area of . Located in Oceania in the southwestern Pacific Ocean, the island is separated from Australia by the wide Torr ...
and the
Philippines
The Philippines (; fil, Pilipinas, links=no), officially the Republic of the Philippines ( fil, Republika ng Pilipinas, links=no),
* bik, Republika kan Filipinas
* ceb, Republika sa Pilipinas
* cbk, República de Filipinas
* hil, Republ ...
, although it does not appear to venture off shore. It is often seen in estuaries and bays in
Borneo
Borneo (; id, Kalimantan) is the third-largest island in the world and the largest in Asia. At the geographic centre of Maritime Southeast Asia, in relation to major Indonesian islands, it is located north of Java, west of Sulawesi, and ea ...
Island, with sightings from
Sandakan
Sandakan (, Jawi: , ) formerly known at various times as Elopura, is the capital of the Sandakan District in Sabah, Malaysia. It is the second largest city in Sabah after Kota Kinabalu. It is located on the Sandakan Peninsula and east coast of ...
in Sabah,
Malaysia
Malaysia ( ; ) is a country in Southeast Asia. The federation, federal constitutional monarchy consists of States and federal territories of Malaysia, thirteen states and three federal territories, separated by the South China Sea into two r ...
, to most parts of
Brunei
Brunei ( , ), formally Brunei Darussalam ( ms, Negara Brunei Darussalam, Jawi: , ), is a country located on the north coast of the island of Borneo in Southeast Asia. Apart from its South China Sea coast, it is completely surrounded by t ...
and
Sarawak
Sarawak (; ) is a state of Malaysia. The largest among the 13 states, with an area almost equal to that of Peninsular Malaysia, Sarawak is located in northwest Borneo Island, and is bordered by the Malaysian state of Sabah to the northeast, ...
, Malaysia. A specimen was collected at
Mahakam River
The Mahakam River ( Indonesian: ''Sungai Mahakam'') is third longest and volume discharge river in Borneo after Kapuas River and Barito River, it is located in Kalimantan, Indonesia. It flows from the district of Long Apari in the highlands o ...
in
East Kalimantan
East Kalimantan ( Indonesian: ) is a province of Indonesia. Its territory comprises the eastern portion of Borneo. It had a population of about 3.03 million at the 2010 census (within the current boundary), 3.42 million at the 2015 census, and 3 ...
.
Presence of the species in Chinese, Taiwanese, and Hong Kong's waters has been questioned as the reported sightings have been considered unreliable, and the easternmost of ranges along Eurasian continent is in
Vietnam
Vietnam or Viet Nam ( vi, Việt Nam, ), officially the Socialist Republic of Vietnam,., group="n" is a country in Southeast Asia, at the eastern edge of mainland Southeast Asia, with an area of and population of 96 million, making i ...
.
No range-wide survey has been conducted for this vulnerable species; however, the worldwide population appears to be over 7,000. In India, Irawaddy dolphins are mostly found in
Chilika Lake. Known subpopulations of Irrawaddy dolphins are found in eight places, listed here in order of population, including
conservation status
The conservation status of a group of organisms (for instance, a species) indicates whether the group still exists and how likely the group is to become extinct in the near future. Many factors are taken into account when assessing conservatio ...
.
![Chilika lake](https://upload.wikimedia.org/wikipedia/commons/f/f6/Chilika_lake.png)
#
Bangladesh
Bangladesh (}, ), officially the People's Republic of Bangladesh, is a country in South Asia. It is the eighth-most populous country in the world, with a population exceeding 165 million people in an area of . Bangladesh is among the mos ...
: ~3500 (
VU) in coastal waters of the Bay of Bengal and 451 (VU) in the brackish
Sundarbans
Sundarbans (pronounced ) is a mangrove area in the delta formed by the confluence of the Padma, Brahmaputra and Meghna Rivers in the Bay of Bengal. It spans the area from the Baleswar River in Bangladesh's division of Khulna to the Hooghly R ...
mangrove forest
#
India
India, officially the Republic of India (Hindi: ), is a country in South Asia. It is the seventh-largest country by area, the second-most populous country, and the most populous democracy in the world. Bounded by the Indian Ocean on the so ...
: 156 (VU) in the brackish-water
Chilika Lake,
Odisha
Odisha (English: , ), formerly Orissa ( the official name until 2011), is an Indian state located in Eastern India. It is the 8th largest state by area, and the 11th largest by population. The state has the third largest population of ...
. Presence recorded from
Sundarbans National Park
The Sundarbans National Park is a national park, tiger reserve and biosphere reserve in West Bengal, India. It is part of the Sundarbans on the Ganges Delta and adjacent to the Sundarban Reserve Forest in Bangladesh. It is located to south-w ...
,
West Bengal
West Bengal (, Bengali: ''Poshchim Bongo'', , abbr. WB) is a state in the eastern portion of India. It is situated along the Bay of Bengal, along with a population of over 91 million inhabitants within an area of . West Bengal is the fou ...
also.
#
Laos,
Cambodia
Cambodia (; also Kampuchea ; km, កម្ពុជា, UNGEGN: ), officially the Kingdom of Cambodia, is a country located in the southern portion of the Indochinese Peninsula in Southeast Asia, spanning an area of , bordered by Thailan ...
: 92 (
CR) in a 190-km (118-mi) freshwater stretch of the
Mekong River
The Mekong or Mekong River is a trans-boundary river in East Asia and Southeast Asia. It is the world's twelfth longest river and the third longest in Asia. Its estimated length is , and it drains an area of , discharging of water annual ...
#
Indonesia
Indonesia, officially the Republic of Indonesia, is a country in Southeast Asia and Oceania between the Indian and Pacific oceans. It consists of over 17,000 islands, including Sumatra, Java, Sulawesi, and parts of Borneo and New Guine ...
: ~70 (CR), in a 420-km (260-mi) stretch of the freshwater
Mahakam River
The Mahakam River ( Indonesian: ''Sungai Mahakam'') is third longest and volume discharge river in Borneo after Kapuas River and Barito River, it is located in Kalimantan, Indonesia. It flows from the district of Long Apari in the highlands o ...
#
Philippines
The Philippines (; fil, Pilipinas, links=no), officially the Republic of the Philippines ( fil, Republika ng Pilipinas, links=no),
* bik, Republika kan Filipinas
* ceb, Republika sa Pilipinas
* cbk, República de Filipinas
* hil, Republ ...
: ~42 (CR) in the brackish inner
Malampaya Sound. Researchers are studying the recent discovery of 30-40 dolphins sighted in the waters of
Pulupandan
Pulupandan, officially the Municipality of Pulupandan ( hil, Banwa sang Pulupandan; tl, Bayan ng Pulupandan), is a 3rd class municipality in the province of Negros Occidental, Philippines. According to the 2020 census, it has a population of 30 ...
and
Bago, Negros Occidental, in Western Visayas.
#
Myanmar
Myanmar, ; UK pronunciations: US pronunciations incl. . Note: Wikipedia's IPA conventions require indicating /r/ even in British English although only some British English speakers pronounce r at the end of syllables. As John Wells explai ...
(Burma): ~58-72 (CR) in a 370-km (230-mi) freshwater stretch of the
Ayeyarwady River
The Irrawaddy River ( Ayeyarwady River; , , from Indic ''revatī'', meaning "abounding in riches") is a river that flows from north to south through Myanmar (Burma). It is the country's largest river and most important commercial waterway. Orig ...
#
Thailand
Thailand ( ), historically known as Siam () and officially the Kingdom of Thailand, is a country in Southeast Asia, located at the centre of the Indochinese Peninsula, spanning , with a population of almost 70 million. The country is b ...
: less than 50 (CR) in the brackish
Songkhla Lake
Songkhla Lake ( th, ทะเลสาบสงขลา, , ) is the largest natural lake in Thailand. It is on the Malay peninsula in the southern part of the country. Covering an area of 1,040 km2 it borders the provinces of Songkhla and Pha ...
Interaction with humans
Irrawaddy dolphins have a
mutualistic relationship of co-operative fishing with traditional fishers. Fishers in India recall when they would call out to the dolphins, by tapping a wooden key also known as a ''lahai kway'', against the sides of their boats, asking the Irrawaddys to drive fish into their nets. In Burma, in the upper reaches of the Ayeyarwady River, Irrawaddy dolphins drive fish towards fishers using
cast net
A casting net, also called a throw net, is a net used for fishing. It is a circular net with small weights distributed around its edge.
The net is cast or thrown by hand in such a manner that it spreads out while it's in the air before it sinks ...
s in response to acoustic signals from them. The fishermen attempt to gain the attention of the dolphins through various efforts such as using a cone-shaped wooden stick to drum the side of their canoes, striking their paddles to the surface of the water, jingling their nets, or making calls that sound turkey-like. A herd of dolphins that agrees to work alongside the fisherman will entrap a school of fish in a semicircle, guiding them towards the boat.
In return, the dolphins are rewarded with some of the fishers'
bycatch. Historically, Irrawaddy River fishers claimed particular dolphins were associated with individual fishing villages and chased fish into their nets. An 1879 report indicated legal claims were frequently brought into native courts by fishers to recover a share of the fish from the nets of a rival fisher that the plaintiff's dolphin was claimed to have helped fill.
Threats
![BD-fishermen](https://upload.wikimedia.org/wikipedia/commons/f/fd/BD-fishermen.jpg)
Irrawaddy dolphins are more susceptible to human conflict than most other dolphins that live farther out in the ocean. Drowning in
gillnets is the main threat to them throughout their range. Between 1995 and 2001, 38 deaths were reported and 74% died as a result of entanglement in gillnets with large mesh sizes.
The majority of reported dolphin deaths in all subpopulations is due to accidental capture and drowning in gillnets and
dragnets, and in the Philippines, bottom-set crabnets. In Burma,
electrofishing
Electrofishing is a fishing technique that uses direct current electricity flowing between a submerged cathode and anode. This affects the movements of nearby fish so that they swim toward the anode, where they can be caught or stunned. ,
gold mining
Gold mining is the extraction of gold resources by mining. Historically, mining gold from alluvial deposits used manual separation processes, such as gold panning. However, with the expansion of gold mining to ores that are not on the surface, ...
, and dam building are also serious and continuing threats. Though most fishers are sympathetic to the dolphins' plight, abandoning their traditional livelihood is difficult for them.
Another identified threat towards the Irrawaddy dolphins was noise pollution from high-speed vessels. This caused the dolphins to dive significantly longer than usual. The Irrawaddy dolphins always changed directions when they encountered these large vessels.
Laotians and Cambodians have a common belief that the Irrawaddy dolphins are reincarnations of their ancestors. Some even claim that the dolphins have saved drowning villagers and protected people from attacks by crocodiles. Their beliefs and experiences have led the people of Laos and Cambodia to live peacefully alongside one another for ages until recent years, when the technique of using explosives for fishing has emerged. The government of Laos has made use of such tactics illegal, but few regulations have been made in neighboring Cambodia, where explosives are sold in local markets and the practice of using fishnets has been abandoned. The practice of using explosives instead has become very popular and led to a steady decline of populations of fish, and especially the dolphins swimming in the area. Although Laotians may not use explosives, they do use nylon gillnets, which pose another large threat to the survival of the Irrawaddy. Some dolphins accidentally become entangled in the net. Poor fishermen refuse to cut and destroy their nets because it would result in too great of an economic loss to save one Irrawaddy dolphin.
In Laos, a dam across the Mekong River is planned. This could threaten the existence of the endangered Irrawaddy dolphins in downstream Cambodia. Laos's government decision is to forge the dam upstream of the core habitat of the Irrawaddy dolphins. This could precipitate the extinction of this specific species in the Mekong River. The dam builders' proposal is to use explosives to dig out the tons of rock. This will create strong sound waves that could possibly kill the Irrawaddy dolphins due to their highly sensitive hearing structures.
In several Asian countries, Irrawaddy dolphins have been captured and trained to perform in
public aquaria
A public aquarium (plural: ''public aquaria'' or ''public Water Zoo'') is the aquatic counterpart of a zoo, which houses living aquatic animal and plant specimens for public viewing. Most public aquariums feature tanks larger than those kept b ...
. Their charismatic appearance and unique behaviors, including spitting water,
spyhopping
Cetacean surfacing behaviour is a grouping of movement types that cetaceans make at the water's surface in addition to breathing. Cetaceans have developed and use surface behaviours for many functions such as display, feeding and communication. ...
, and
fluke-slapping, make them very popular for shows in
dolphinaria. The commercial motivation for using this dolphin species is high because it can live in freshwater tanks and the high cost of
marine aquarium
A marine aquarium is an aquarium that keeps marine plants and animals in a contained environment. Marine aquaria are further subdivided by hobbyists into fish only (FO), fish only with live rock (FOWLR), and reef aquaria. Fish only tanks ofte ...
systems is avoided. The region within and near the species' range has developed economically; theme parks, casinos, and other entertainment venues that include dolphin shows have increased.
Khmer and Vietnamese fishermen have regarded the ''Orcaella'' as a sacred animal. If caught in fishing nets, they release the dolphin from the rest of the catch. In contrast, Khmer-Islam fisherman kill them for food. This has led to the dolphin being reputed to recognize the local languages of the area and approach the Khmer-Islam with caution. In 2002, there were more than 80 dolphinariums in at least nine Asian countries.
Collateral deaths of dolphins due to
blast fishing
Blast fishing, fish bombing, dynamite fishing or grenade fishing is a destructive fishing practice using explosives to stun or kill schools of fish for easy collection. This often illegal practice is extremely destructive to the surrounding e ...
were once common in
Vietnam
Vietnam or Viet Nam ( vi, Việt Nam, ), officially the Socialist Republic of Vietnam,., group="n" is a country in Southeast Asia, at the eastern edge of mainland Southeast Asia, with an area of and population of 96 million, making i ...
and
Thailand
Thailand ( ), historically known as Siam () and officially the Kingdom of Thailand, is a country in Southeast Asia, located at the centre of the Indochinese Peninsula, spanning , with a population of almost 70 million. The country is b ...
. In the past, the most direct threat was killing them for their oil.
The
IUCN lists five of the seven subpopulations as
endangered
An endangered species is a species that is very likely to become extinct in the near future, either worldwide or in a particular political jurisdiction. Endangered species may be at risk due to factors such as habitat loss, poaching and in ...
, primarily due to drowning in fish nets.
For example, the Malampaya population, first discovered and described in 1986, at the time consisted of 77 individuals. Due to anthropogenic activities, this number dwindled to 47 dolphins in 2007.
In the Mahakam River in Borneo, 73% of dolphin deaths are related to entanglement in gillnets, due to heavy fishing and boat traffic.
Tourism
The Irrawaddy dolphins in Asia are increasingly threatened by tourist activity, such as large numbers of boats circulating the areas in which they live. The development of tours and boats has put a large strain on the dolphins.
Disease
Cutaneous nodules were found present in various vulnerable populations of Irrawaddy dolphins. A more precise estimate of the affected dolphins is six populations. Although the definite fate of this emergent disease is unknown, the species is at risk.
Conservation
The Irrawaddy dolphin's proximity to developing communities makes the effort for conservation difficult. Entanglement in fishnets and degradation of habitats are the main threats to Irrawaddy dolphins. Conservation efforts are being made at international and national levels to alleviate these threats.
International efforts
Protection from international trade is provided by the Convention on International Trade in Endangered Species of Wild Fauna and Flora (
CITES
CITES (shorter name for the Convention on International Trade in Endangered Species of Wild Fauna and Flora, also known as the Washington Convention) is a multilateral treaty to protect endangered plants and animals from the threats of interna ...
). Enforcement, though, is the responsibility of individual countries.
While some international trade for dolphinarium animals may have occurred, this is unlikely to have ever been a major threat to the species.
Some Irrawaddy dolphin populations are classified by the IUCN as critically endangered; in Lao PDR, Cambodia, Viet Nam (Mekong River sub-population), Indonesia (Mahakam River sub-population, Borneo), Myanmar (Ayeyarwady/Irrawaddy River sub-population), the Philippines (Malampaya Sound sub-population), and Thailand (Songkhla Lake sub-population). Irrawaddy dolphins in general however, are IUCN listed as an
Endangered species, which applies throughout their whole range.
In 2004, CITES transferred the Irrawaddy dolphin from
Appendix II
CITES (shorter name for the Convention on International Trade in Endangered Species of Wild Fauna and Flora, also known as the Washington Convention) is a multilateral treaty to protect endangered plants and animals from the threats of interna ...
to
Appendix I, which forbids all commercial trade in species that are threatened with extinction.
The
UNEP
The United Nations Environment Programme (UNEP) is responsible for coordinating responses to environmental issues within the United Nations system. It was established by Maurice Strong, its first director, after the United Nations Conference on ...
-
CMS
CMS may refer to:
Computing
* Call management system
* CMS-2 (programming language), used by the United States Navy
* Code Morphing Software, a technology used by Transmeta
* Collection management system for a museum collection
* Color manag ...
Action Plan for the Conservation of Freshwater Populations of Irrawaddy dolphins notes that multiple-use
protected areas
Protected areas or conservation areas are locations which receive protection because of their recognized natural, ecological or cultural values. There are several kinds of protected areas, which vary by level of protection depending on the ena ...
will play a key role for conserving freshwater populations. Protected areas in fresh water could be a particularly effective conservation tool and can facilitate management, due to the fidelity of the species to relatively circumscribed areas. The Action Plan provides details on strategies for mitigating
by-catch
Bycatch (or by-catch), in the fishing industry, is a fish or other marine species that is caught unintentionally while fishing for specific species or sizes of wildlife. Bycatch is either the wrong species, the wrong sex, or is undersized or juve ...
that includes:
:-establishing core conservation areas where gillnetting is banned or severely restricted
:-promoting net attendance rules and providing training on the safe release of entangled dolphins
:-initiating programs to compensate fishers for damage caused to their nets by entangled dolphins that are safely released
:-providing alternative or diversified employment options for gillnet fishers
:-encouraging the use of fishing gear that does not harm dolphins, by altering or establishing fee structures for fishing permits to make gillnetting more expensive while decreasing the fees for nondestructive gear
:-experimenting with acoustical deterrents and reflective nets.
The Irrawaddy dolphin is listed on both Appendix I and Appendix II of the Convention on the Conservation of Migratory Species of Wild Animals (
CMS
CMS may refer to:
Computing
* Call management system
* CMS-2 (programming language), used by the United States Navy
* Code Morphing Software, a technology used by Transmeta
* Collection management system for a museum collection
* Color manag ...
).
It is listed on Appendix I
as this species has been categorized as being in danger of extinction throughout all or a significant proportion of their range and CMS Parties strive towards strictly protecting these animals, conserving or restoring the places where they live, mitigating obstacles to migration and controlling other factors that might endanger them, as well on Appendix II
as it has an unfavourable conservation status or would benefit significantly from international co-operation organized by tailored agreements.
The species is also covered by the Memorandum of Understanding for the Conservation of Cetaceans and Their Habitats in the Pacific Islands Region (MoU).
National efforts
Several national efforts are resulting in the reduction of threats to local Irrawaddy dolphin subpopulations:
Bangladesh
![Sundarbans](https://upload.wikimedia.org/wikipedia/commons/a/a2/Sundarbans.jpg)
Portions of Irrawaddy dolphin habitat in the
Sundarbans
Sundarbans (pronounced ) is a mangrove area in the delta formed by the confluence of the Padma, Brahmaputra and Meghna Rivers in the Bay of Bengal. It spans the area from the Baleswar River in Bangladesh's division of Khulna to the Hooghly R ...
mangrove forest of Bangladesh are included within of
three wildlife sanctuaries, which are part of the
Sunderbans World Heritage Site. The
Wildlife Conservation Society
The Wildlife Conservation Society (WCS) is a non-governmental organization headquartered at the Bronx Zoo in New York City, that aims to conserve the world's largest wild places in 14 priority regions. Founded in 1895 as the New York Zoological ...
is working with the Bangladesh Ministry of Environment and Forests to create protected areas for the 6000 remaining dolphins
[
]
Cambodia
Irrawaddy dolphins are fully protected as an endangered species under Cambodian fishery law. In 2005, The World Wide Fund For Nature
The World Wide Fund for Nature Inc. (WWF) is an international non-governmental organization founded in 1961 that works in the field of wilderness preservation and the reduction of human impact on the environment. It was formerly named the Wor ...
(WWF) established the Cambodian Mekong Dolphin Conservation Project with support from government and local communities. The aim is to support the survival of the remaining population through targeted conservation activities, research, and education. In January 2012, the Cambodian Fisheries Administration, the Commission for Conservation and Development of Mekong River Dolphin Eco-tourism Zone, and WWF signed the Kratie Declaration on the Conservation of the Mekong River Irrawaddy Dolphin, an agreement binding them to work together, and setting out a roadmap for dolphin conservation in the Mekong River. On 24 August 2012, the Cambodian government announced that stretch of the Mekong River from eastern Kratie province to the border with Laos has been stated as limit fishing zone which uses floating houses, fishing cages and gill nets are disallowed, but simple fishing is allowed. This area is patrolled by a network of river guards, specifically to protect dolphins. Between January and February 2006, a dozen Irrawaddy dolphins were found dead. The discovery of 10 new baby dolphins on the coast of Cambodia was a relief and gave hope that the endangered Irrawaddy dolphins would make a comeback in population. Since the endangerment was evident, 66 guards have been posted on the coast of Cambodia to protect these dolphins, and only two deaths have been reported since these efforts. To make more efforts to keep these animals from going extinct, the use of fishing nets on the coast of Cambodia is banned, as well.
India
The Irrawaddy dolphin (under the common name of snubfin dolphin, with the scientific name misspelled as ''Oreaella brevezastris'') is included the Indian Wildlife Protection Act, Schedule I, which bans their killing, transport and sale of products.[ A major restoration effort to open a new mouth between Chilika Lake and the Bay of Bengal in 2000 was successful in restoring the lake ecology and regulating the salinity gradient in the lake waters, which has resulted in increases in the population of Irrawaddy dolphin due to increase of prey species of fish, prawns, and crabs.]
Indonesia
A conservation program, entitled Conservation Foundation for the Protection of Rare Aquatic Species of Indonesia, focused on protecting the Irrawaddy dolphin population and their habitat, the Mahakam River. The program not only educates and surveys the public, but also monitors the dolphin population and their habitat. A prime example of this is the establishment of patrols in several villages.
Laos
Some major concern for the population in the Mekong River has arisen due to numerous threats. In the 1970s, many Irrawaddy dolphins were slaughtered for oil, and soon after, intensive fishing practices with explosives and gillnets began. As of now, the dolphins are protected in Cambodia and Laos Democratic Republic. Now, both explosive fishing and use of gillnets is restricted in many of the Irrawaddy dolphin's habitats. Canadian conservationist Ian Baird set up the Lao Community Fisheries and Dolphin Protection Project to study the Irrawaddy dolphins in the Laotian part of the Mekong. Part of this project compensated fishers for the loss of nets damaged to free entangled dolphins. This project was expanded to include Cambodia, after the majority of the dolphin population was determined to have been killed or migrated to Laos' southern neighbor. The Si Phan Don The Si Phan Don ( lo, ສີ່ພັນດອນ; meaning '4,000 islands') is a riverine archipelago in the Mekong River, Champasak Province in southern Laos. Si Phan Don is part of Khong District, including the islands and part of the mainland ...
Wetlands Project has successfully encouraged river communities to set aside conservation zones and establish laws to regulate how and when fish are caught. In April, after a 200-kg Irrawaddy dolphin was found dead on the coast of Laos, the death toll for Irrawaddy dolphins is now five in 2015. Usually, Irrawaddy dolphins are found dead with bruises and scars on their body, being killed by illegal poaching, but this Irrawaddy dolphin was found dead because of old age. She is the oldest and largest Irrawaddy dolphin researchers have discovered. The dolphin was in length and most likely in her late 20s.
Myanmar
Myanmar's Department of Fisheries took charge in December 2005, and instituted a protected region in a segment of the Ayeyarwady River between Mingun
Mingun ( ) is a town in Sagaing Township of Sagaing Region, north-west Myanmar (Burma), located 11 km up the Ayeyarwady River on the west bank from Mandalay. Its main attraction is the ruined Mingun Pahtodawgyi.
Mingun Pahtodawgyi
The Ming ...
and Kyaukmyaung and created multiple provisions, as well. Protective measures in the area include mandatory release of entangled dolphins, prohibition of the catching or killing of dolphins and trade in whole or parts of them, and the prohibition of electrofishing and gillnets more than long, or spaced less than apart.[ Mercury poisoning and habitat loss from gold-mining dredging operations in the river have been eliminated]
Philippines
In 2000, Malampaya Sound was proclaimed a protected seascape. This is the lowest possible prioritization given to a protected area. Malampaya Sound Ecological Studies Project was initiated by the WWF. With technical support provided by the project, the municipality of Taytay and the Malampaya park management developed fishery policies to minimize the threats to the Irrawaddy dolphin from bycatch capture. Gear studies and gear modification to conserve the dolphin species were implemented. The project was completed in 2007.
In 2007, the Coral Triangle
The Coral Triangle (CT) is a roughly triangular area in the tropical waters around the Philippines, Indonesia, Malaysia, Papua New Guinea, the Solomon Islands and Timor-Leste. This area contains at least 500 species of reef-building corals in e ...
Initiative, a new multilateral partnership to help safeguard the marine and coastal resources of the Coral Triangle, including the Irrawaddy dolphin subpopulation in Malampaya Sound, was launched. In 2006, a new population was discovered in Guimaras
Guimaras , officially the Province of Guimaras ( hil, Kapuoran sang Guimaras; tl, Lalawigan ng Guimaras), is an island province in the Philippines located in the Western Visayas region. Its capital is Jordan while its largest local government ...
island in the Visayas. In 2015, another new population was discovered in Bago in Negros Occidental
Negros Occidental ( hil, Nakatungdang Negros; tl, Kanlurang Negros), officially the Province of Negros Occidental, is a Provinces of the Philippines, province in the Philippines located in the Western Visayas Regions of the Philippines, region. ...
, part of Negros island in the Visayas.
Thailand
In 2002, the Marine and Coastal Resources Department was assigned to protect rare aquatic animals such as dolphins, whales, and turtles in Thai territorial waters. To protect the dolphins, patrol vessels ensure boats stay at least away from dolphins and no chasing of or running through schools of dolphins occurs. Many fishermen on the Bang Pakong River
The Bang Pakong ( th, แม่น้ำบางปะกง, , ) is a river in east Thailand. The river originates at the confluence of the Phra Prong River and the Hanuman River near Kabin Buri, Prachinburi Province. It empties after 231 k ...
, Prachinburi Province
Prachinburi province ( th, ปราจีนบุรี, , ) is one of Thailand's seventy-seven provinces (''changwat''), it lies in eastern Thailand. Neighboring provinces are (from north clockwise) Nakhon Ratchasima, Sa Kaeo, Chachoengsao, an ...
, have been persuaded by authorities to stop shrimp fishing
The shrimp fishery is a major global industry, with more than 3.4 million tons caught per year, chiefly in Asia. Rates of bycatch are unusually high for shrimp fishing, with the capture of sea turtles being especially contentious.
A shrimper is a ...
in a certain area and 30 to 40 fishing boats have been modified so they can offer dolphin sightseeing tours.
A total of 65 Irrawaddi dolphins has been found dead along the coast of Trat Province in the past three years. The local fishing industry is blamed for the deaths of the dolphins. In January 2013, over a dozen dead Irrawaddy dolphins were found on the coast of Thailand. These dolphins were said to be dead because of a lack of oxygen. Dolphins are mammals, and unlike other animals that live in the sea, they must come to the surface for air. Many of the dolphins are found dead in the water, and others were washed ashore, said to have been dead for a few days. Also, in the first week of February 2013, as many as four Irrawaddy dolphins were found dead. The Natural Resources and Environment Ministry is studying artificial breeding options in 2022 to try to save the last herd of Irrawaddy dolphins in Songkhla Lake, which is on the verge of extinction after only 14 were found in the most recent survey. They also intend to list dolphins as a protected species
An endangered species is a species that is very likely to become extinct in the near future, either worldwide or in a particular political jurisdiction. Endangered species may be at risk due to factors such as habitat loss, poaching and invas ...
, Thailand's highest level of animal protection.
Malaysia
In 2008, the Department of Forestry and Sarawak Forestry Cooperative in Sarawak established a protected area for Irrawaddy dolphins in Santubong and Damai (Kuching Wetland).[ Furthermore, they plan to establish more beaches in Miri as protected areas for them. The protection measures in the area include prohibition of catching or killing of dolphins and trade in whole or parts of them, and prohibiting the use of gillnets. The government may also start small- and medium-scale research of this species at Sarawak Malaysia University with sponsorship from Sarawak Shell.
]
Vietnam
In 2012 in Vietnam, a group of scientists took in four Irrawaddy dolphins and provided them with medical care to see how they would survive. However, they found this to be the first case they saw of Irrawaddy dolphins having bacterial infections. The bacterial infection, chorioamnionitis, is common in many marine animals, but when these few dolphins were taken in, the scientists discovered this same bacterial infection for the first time in this group of dolphins. This disease mostly affects animals that are pregnant because the infection occurs through the umbilical cord and goes into the maternal bloodstream. One of the dolphins was pregnant and before her death was found circling around the bottom of the pool and was found dead early the next morning. This bacterial infection affects many organs in the body of the animal.
See also
*List of cetaceans
Cetacea is an infraorder that comprises the 94 species of whales, dolphins, and porpoises. It is divided into toothed whales (Odontoceti) and baleen whales (Mysticeti), which diverged from each other in the Eocene some 50 million years ago (m ...
* Marine biology
*Environmental issues in Indonesia
Environmental issues in Indonesia are associated with the country's high population density and rapid industrialisation, and they are often given a lower priority due to high poverty levels, and an under-resourced governance.
Most large palm oi ...
*South Asian river dolphin
South Asian river dolphins are toothed whales in the genus ''Platanista'', which inhabit fresh water habitats in the northern Indian subcontinent. They were historically considered to be one species (''P. gangetica'') with the Ganges river dol ...
References
Bibliography
* ''Encyclopedia of Marine Mammals'', .
* ''National Audubon Society Guide to Marine Mammals of the World'', .
* ''Whales, Dolphins and Porpoises'', Mark Carwardine, .
External links
Video of Irrawaddy dolphin behavior
WWF-US Irrawaddy dolphin page
Whale and Dolphin Conservation Society
describes human/dolphin cooperative fishing
* Worldwide Bycatch of Cetaceans, National Marine Fisheries Service
The National Marine Fisheries Service (NMFS), informally known as NOAA Fisheries, is a United States federal agency within the U.S. Department of Commerce's National Oceanic and Atmospheric Administration (NOAA) that is responsible for the ste ...
, NOAA Tech. Memo. NMFS-OPR-36 July 200
65 Irrawaddy dolphin mentions
Dolphin World Irrawaddy Dolphin
WDC About Irrawaddy Dolphin
*
{{Authority control
Irrawaddy dolphin
The Irrawaddy dolphin (''Orcaella brevirostris'') is a euryhaline species of oceanic dolphin found in scattered subpopulations near sea coasts and in estuaries and rivers in parts of the Bay of Bengal and Southeast Asia. It closely resembles the ...
Irrawaddy River
Bay of Bengal
Sundarbans
Mammals of India
Mammals of Bangladesh
Mammals of South Asia
Fauna of South Asia
Mammals of Southeast Asia
Maritime Southeast Asia
Vulnerable fauna of Asia
Irrawaddy dolphin
The Irrawaddy dolphin (''Orcaella brevirostris'') is a euryhaline species of oceanic dolphin found in scattered subpopulations near sea coasts and in estuaries and rivers in parts of the Bay of Bengal and Southeast Asia. It closely resembles the ...