September 02, 2010

THE CHILDREN OF THE GANGA


THE GANGES RIVER DOLPHIN


Ever since the dawn of civilization in the Indian Sub-continent, the Ganga has played a pivotal role in the political, religious, cultural and economic matters concerning the people of the region. Apart from being a perennial source of water, the fertile alluvium brought down by this mighty river has made the North Indian plain, one of the most productive, prosperous and populous region of the world. Since time immemorial, the wealth and grandeur of cites of the Ganga valley have lured people from different parts of the world towards India. In fact the Ganga plain is the crucible from which the ‘Great Civilization of India’, based on the virtues of equality, love and freedom came into existence. Besides being the holiest river in Hinduism, the Ganga, India’s National River finds a mention in all the ancient Vedic texts and continues to be our symbol all over the world.

While the various aspects of the Ganga and its relevance in the Story of India are well documented, the fact most often overlooked about the river is the rich bio-diversity that it supports in its 2500 km long journey that encompasses several different vegetative patterns including the confiners in the higher altitudes of the Himalayas to the Sundri trees of the Sunderban delta region. Perhaps, the most well-known of all faunal species that inhabits it, is our National Aquatic animal – The Ganga River dolphin.

Unlike their oceanic cousins who are occasionally sighted in fresh waters near the mouth of rivers, the river dolphins of the world, classed in the Platanistoidea super family of cetaceans reside in fresh water rivers and estuaries. The two types of dolphins differ somewhat in physical appearance with river dolphins having a much larger snout of about 30 centimeters. On the contrary, they have smaller eyes, and their vision is poorly developed because they live in dark, muddy water. This environment also makes river dolphins less active than marine dolphins.

Of the four species of the river dolphins the largest is the Boto or The Amazon River dolphin endemic to the Orinoco, Amazon and Araguaia/Tocantins River systems of South America. The other fresh water dolphin found in this continent is the La Plata or Franciscana dolphin, which is also found in the ocean and saltwater estuaries. The third member is the Baiji or Chinese River dolphin that once inhabited the Yangtze River, but fell prey to China’s rapid industrialization and was declared “functionally extinct” in December 2006. And lastly, the South Asian River dolphins, the two sub-species of freshwater dolphins found in two great rivers of the Sub-continent, the Ganga and the Sindhu. The Ganges River dolphin or the Ganges Susu is primarily found in the Ganges and Brahmaputra Rivers and their tributaries in India, Bangladesh and Nepal, while the Indus River dolphin or Bhulan is found in the Indus River in Pakistan and its Beas and Sutlej tributaries. From the 1970s until 1998, they were regarded as separate species; however, in 1998, their classification was changed from two separate species to subspecies of a single species.
Credit: Francois Xavier / WWF India
Having a fairly thick, yet sturdy body with light grey-brown skin, often with a hue of pink, river dolphins of the Ganga, like other species of this kind are characterized by a large snout that thickens towards its end. The teeth are visible in both the upper and lower jaws even when the mouth is closed. The flippers and tail are thin and large in relation to the body size while the dorsal fin is under developed and reduced to a triangular lump. These aquatic mammals display sexual dimorphism with the mature adult females being much larger than the males because the female rostrum continues to grow even after the male rostrum stops growing, eventually reaching approximately 20 centimeters more. Having an average weight of about 150 kilograms, the species have been recorded to live for as many as 28 years in captivity. The males attain sexual maturity at an age of about 10 to 12 years, while the females mature much earlier. After a gestation period that is thought to be approximately 10 months, the dolphins give birth to a single calf, once in 2 to 3 years. The young which are chocolate brown at the time of the birth become grayish brown in adulthood with a smooth and hairless skin. The teeth of the young are almost an inch long, thin and curved; however, as the animals age the teeth undergo considerable changes and in mature adults become square, bony and flat disks. Calves have been observed between January and May and do not appear to stay with the mother for more than a few months.

In fact what sets this creature apart from all others that inhabit the river is the unique manner in which they navigate and catch their prey in the muddy waters of the holy Ganga. These mammals do not have a crystalline eye lens, rendering them effectively blind and earning it the nickname – The Blind River dolphin, although the eyes may still be able to detect the intensity and direction of light. As such, navigation and hunting are carried out using the technique of echolocation – commonly known as the Biosonar, and found in many other animal species like bats, whales, porpoises etc. This technique comes in handy as they live in an underwater habitat that has favourable acoustic characteristics and where vision is extremely limited in range due to absorption and turbidity. The dolphin emits an ultrasonic sound from its snout in the directions of its head, which reaches the prey or any obstacle in the path and is reflected back. The echoes are received using fatty structures around the lower jaw as the primary reception path, from where they are transmitted to the brain. The dolphin then registers this image in its mind and subsequently avoids the obstacles or catches hold of its prey which includes a variety of shrimp and fish, including the carp, catfish, mahseers, gobies and freshwater shark. It does much of its feeding at or near the bottom, swimming on one side, and probing the river bottom with its snout and flipper, which has led to them being referred to as - The Side Swimming dolphins.

The marked seasonal changes in the distribution and density of the Ganges River dolphin over much of its range are due, at least in large part, to fluctuations in water levels. During the dry season from October - April, many dolphins leave the tributaries of the Ganges - Brahmaputra system and congregate in the main channels, only to return to the tributaries the following rainy season. They may become isolated in pools and river branches during the dry season. Reports from the 19th century speak of large schools of dolphins to be seen near most large towns on the Ganga River. However, in more recent times, this dolphin has usually been found to occur in small groups or alone with relatively high densities being recorded at sites near the confluence of two or more rivers, in areas where the current is relatively weak, off the mouths of irrigation canals, and near villages and ferry routes, sharing their habitat with other critically endangered species like gharials, fresh water turtles. In India, their distribution range covers seven states and several rivers – The Upper Ganga River (Uttar Pradesh), Chambal River (Madhya Pradesh and Uttar Pradesh), Ghagra and Gandak Rivers (Bihar and Uttar Pradesh), Ganga River (Varanasi to Patna), Sone and Kosi Rivers (Bihar), Brahmaputra River from Sadia (Arunachal Pradesh) to Dhubri (Bangladesh border) and its tributary, Kulsi River.

Once present in tens of thousands of numbers, the Ganges River dolphin has dwindled abysmally to less than 2000 during the last century. Probably the greatest factor that goes against it is the fact that its habitat – The Indo-Gangetic Plain, supports nearly one-tenth of the world human population. Though deliberate killing of this species for meat and oil seem to have declined in most of the areas, the various reasons that have contributed to a steady decline in their numbers are as follows:-

(1) Habitat Fragmentation: The construction of 50 or more dams and barrages within the Ganges River dolphin’s historic range has drastically altered its habitat and fragmented the population. More such structures are planned or are under consideration. Approximately 3500 km of embankments have been constructed along the main channel of the Ganges and its tributaries which interrupts access to spawning habitat for floodplain-dependent fishes and eliminate eddy counter-currents where the dolphins spend much of their time.

(2) River Pollution: Dredging and the removal of stones, sand, and woody debris also compromise the ecological integrity of the riverine environments, especially in small tributaries. Concentrations of toxic chemicals such as organochlorine and butyltin in the tissues of Ganges River dolphins are high enough to cause concern about adverse effects.

(3) Indiscriminate Fishing/Entanglement: Incidental mortality in fishing gear, especially gillnets, is a severe problem for the Ganges River dolphin throughout most of its range. The demand for these products means that there is little incentive for fishermen to reduce the by catch or to release dolphins that are still alive when found in nets.
Credit: Roland Seitre
Placed in Schedule-I of the Wildlife Protection Act, 1972, and listed by IUCN as ‘Endangered’, the Ganges River dolphin enjoys high levels of legal protection both nationally and internationally. This species was declared as the National Aquatic Animal of India by a decision taken in the first meeting of the National Ganga River Basin Authority (NGRBA) chaired by Dr. Manmohan Singh on 5th October, 2009. It has been recently found that fish oils can be used in the place of dolphin oil for the preparation of bait. Popularization of fish oil as bait may reduce the poaching of dolphins for its oil.

Yet its numbers continue to decline. The absence of a coordinated conservation plan, lack of awareness and continuing anthropogenic pressure, are posing an incessant threat to the existing dolphin population. In fact several conservation programs have been launched in the Vikramshila Gangetic dolphin Sanctuary, the only protected area for the Ganges dolphin in India, to study these creatures, to understand their behavior and to protect them. These include:-

(1) The Vikramshila Biodiversity Research and Education Centre (VBREC), led by Dr. Sunil Chaudhary, together with the Whale and dolphin Conservation Society (WDCS), the Environmental Biology Laboratory of Patna University, and T.M. Bhagalpur University, has initiated a project to improve the conservation value of Vikramshila Gangetic dolphin Sanctuary.

(2) Aaranyak, a registered NGO working in the North-East has initiated a project entitled “Conservation of Gangetic dolphin in Brahmaputra” in collaboration with the Dibrugarh University to evaluate the conservation status of these mammals throughout the Brahmaputra River System by carrying out research into its population status, distribution, habitat preferences and threats.

(3) WWF India has also started ‘The Ganges River Dolphin Conservation Program’ to build a scientific database of the population status of the species and study the habitat quality of the dolphins' distribution range. A 'River Watch Program' has been initiated to identify hot spots and develop management plans with the help of the Forest Department and create awareness in target areas.

Dolphins are amongst one of the oldest creatures in the world along with some species of turtles, crocodiles and sharks. In Hindu mythology the Ganges River dolphin is associated with Ganga Mata, the deity of the Ganges River. The dolphin is said to be among the creatures which heralded the goddess' descent from the heavens and her mount, the Makara, is sometimes depicted as a dolphin. In the Rig Veda,the Ganga (Jhanavi) and the River dolphins are mentioned in adjacent verses. This mammal is also said to represent the purity of the holy Ganga as it can only survive in pure and fresh water. It is indeed our duty to protect and preserve this Wonder of the Natural World that Mother Nature has bestowed upon us.



SOURCES


(1) Wikipedia – South Asian River Dolphin (Link)

(2) WWF India – Ganges River Dolphin (Link)

(3) Animal Info: Endangered Animals – Platanista gangetica gangetica (Link)

(4) Indian Government – National Aquatic Animal (Link)

(5) India Divine – The Triveni Sangam (Link)

IMAGES


(2) Credit: Francois Xavier (Link)
Original: Francois Xavier PELLETIER /WWF Canon

(3) Credit: Roland Seitre (Link)
Original: FedePhoto