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Indus River Dolphin

Classification: The specific name, minor, refers to the dolphins' supposedly smaller size. Until the 1970s, this species was thought to be the same as the Ganges River Dolphin.

Description: The Indus River Dolphin has a long beak which thickens toward the tip, revealing the large teeth; the mouthline curves upward. The body is stocky with a rounded belly, the flippers are large and paddle-shaped, and there is a low triangular hump in place of a 'true' dorsal. The forehead is steep and the blowhole is on the left of the head, above the tiny, poorly-seeing eye. The tail flukes are broad in relation to the body size. Indus River Dolphins are grey-brown in colour, sometimes with a pinkish belly,and measure between 1.5 and 2.5m in length,weighing a maximum of 90kg.

Recognition at sea: The Indus River Dolphin is the only cetacean to inhabit the Indus river.

Habitat: These dolphins favour the silt-laden, turbid waters of the Indus river system, at temperatures between 8°C and 33°C.

Threats to the Bulhan:Its habitat has been limited by the construction of barrages to irrigate and provide power to the surrounding farmland.
The river water has been poisoned by pollution from farms, which can cause infertility.
Reduced flow of fresh water brings tidal waves of salt water.
Boatmen competing for diminishing fish stocks sometimes hunt the dolphins.Sometimes dolphins also become trapped when the barrage gates are opened, but the main threat is to breeding, particularly as the chemicals from local cotton farms run off the fields into the river.

Food & Feeding: These dolphins take fish and crustaceans.

Behaviour: Indus River Dolphins travel either as couples or individuals. Since these dolphins do not have a crystalline eye lens they are effectively blind; all they can do is detect the direction and intensity of light. Navigation, therefore, is entirely by a sophisticated echolocation system. This blindness is one of the reasons why these dolphins swim on one side underwater, with one flipper trailing in the muddy riverbed. The physical touch gives the dolphins important information about their surroundings and helps them find food.

Longevity: Unknown.

Estimated Current Population: Approximately 500 animals. Endangered.

Colour: Mid gray-brown.

Eyes: The dolphin is functionally blind and has no lens in its tiny eye.

Teeth: Adults have between 30 and 36 sharp teeth on each side of the rostrum. The teeth are very long, protruding at the end of the rostrum.

Rostrum: River dolphins possess a much longer snout (rostrum) than most oceanic dolphins, up to one fifth of their body length.

Breathe: Dolphins breathe through a blowhole located on the top of their heads.

Neck: The neck is narrow and relatively flexible, easing its movements in the complicated river environment.

The Influence of Man: The Indus River Dolphins have suffered as a result of incidental and direct exploitation. They have been accidentally caught in fishing nets, but have also been hunted for meat, oil and traditional medicines. They are now fully protected in all of their range.

Flippers: The dolphin has very broad flippers to help it stabilise at slow swimming speed.

Reproduction: The gestation period for the dolphins is approximately 10 months and it is believed that the babies are born in spring. When a baby is born it is about 70 cm long (almost the length of a domestic cat and the mother helps it to the surface to breathe. Babies stay close to their mother for the first six months of their life.

Life span: Scientists think that these dolphins can live for approximately 20 years.

Introduction:The Indus River Dolphin is high on the list of the world's endangered species. There are estimated to be fewer than 1000 of these dolphins remaining in the whole of Pakistan, most of them between the Sukkur and Guddu barrages in the south of the country which is now designated a dolphin reserve.The impassable barrages are among the many reasons for the decline in numbers in recent decades. This situation is now thought to have been reversed thanks to its legal protection and efforts of the non-governmental organisation, Adventure Foundation, to bring tourists to view the dolphins and raise the value of these rare mammals in the eyes of the local population.In Bhasti Garib Abad, a small Punjabi village in Pakistan, employment is highly seasonal and the boatmen who for generations had derived a living from the river now struggle to catch enough fish to keep their families. Adventure Foundation Pakistan began a project in October 2000 to train boatmen to take parties of tourists on river safaris in newly renovated wooden boats, to see and hear the dolphins. This has both increased the villagers' regard for the dolphins and brought much-needed benefits to the local economy.

History:Local folklores adds to the dolphin's mysticism. One legend has it that the dolphin was once a woman but a saint cursed her and made her into fish when she refused to give milk to the holy man.

The Indus River dolphin is a very unusual kind of cetacean. It is thought to have its origin in the ancient Tethys Sea, between the Asian continent and the Indian sub-continent, which dried up around fifty million years ago forcing the dolphin to adapt to its only remaining habitat - the rivers. Historically the dolphins existed from the Indus estuary up into the foothills of the Himalayas near Attock in today?s Pakistan. They were also found in all major Indus tributaries, including upstream in the River Ravi in Pakistan and possibly in India. This species represents a unique genome, an irreplaceable part of the biodiversity of life on earth. The Ganges dolphin, a relative of the Indus River dolphin, is another distinct species subspecies of river dolphins as in the Amazon River dolphin and the Yangze River dolphin.

Special Biological Features:Did you know?
People who live by the Indus River call the dolphin "susu" (an Urdu word) after the sound it makes - a sneeze-like breathing sound.

The Indus River dolphin is functionally blind having evolved without a crystalline lens or well-developed light-sensitive organ. A deep fold just above the dolphin's mouth is the remnant of what might once have been eyes down the evolution line. However, this is not a disadvantage but an adaptation to living in the silt-laden turbid waters of the Indus where eyes are virtually useless, as very little light penetrates below the surface of the murky water.


Freshwater Dolphins:The Bulhan or Indus River dolphin (Platanista minor) is one of four freshwater dolphins in the world and is found only in the River Indus in Pakistan. Similar to the Ganges River dolphin (P. gangetica), it is functionally blind - it can distinguish between night and day, but there is no lens in its small eye and it finds its way using echolocation (sonar). It also has an unusual way of swimming on its side, feeling the bottom of the murky river with one of its fins and its long beak.Known locally as the Bulhan or Susu, it feeds on fish such as catfish and carp and crustaceans such as prawns. Before the construction of dams and barrages began in the 1930s, the dolphins would migrate upstream during the monsoon rains and swam back downstream in the dry season. Now their movement is restricted by the barrage's which affects breeding as well as feeding and general health.


References:

Randall R. Reeves, Brent S. Stewart, Phillip J. Clapham and James A. Powell (2002). National Audubon Society Guide to Marine Mammals of the World. Alfred A. Knopf, Inc.

Rice, Dale W. (1998). Marine mammals of the world: systematics and distribution. Society of Marine Mammalogy Special Publication Number 4. 231 pp.