Indus river dolphin

The Indus river dolphin (Platanista minor) is a special kind of freshwater dolphin that lives only in the rivers of the Indus basin in Pakistan and parts of northwestern India. It was the first dolphin ever found that swims on its side.

In Pakistan, these dolphins live in the Indus River, but they are split into five small groups because of dams built for irrigation. In India, a very small group lives in the Beas River, and they are in big danger of disappearing.

For many years, from the 1970s until 1998, people thought the Indus river dolphin and the Ganges River dolphin were two different kinds of animals. But in 1998, scientists decided they were actually two versions of the same animal, called the South Asian river dolphin.

The Indus river dolphin is very important to Pakistan—it is the country’s national mammal. It is also the official aquatic animal of the state of Punjab, India. These dolphins help scientists learn about the health of the rivers they live in.

Taxonomy

The Indus river dolphin was first described in 1853 by Richard Owen. He named it Platanista gangetica, var. minor after seeing a dolphin skull that was smaller than the skulls of the Ganges river dolphin.

At first, people thought the Indus and Ganges river dolphins were the same species, named Platanista gangetica. In the 1970s, scientists said they were different species, but in the 1990s, they were grouped together again. Now, new studies of genes, how long ago they separated, and skull shapes show that they are two distinct species.

The Ganges river dolphin separated from the Indus river dolphin around 550,000 years ago during the Pleistocene.

Description

The Indus river dolphin has a long, pointed nose, like other river dolphins. Its teeth can be seen in both the upper and lower jaws, even when its mouth is closed. Young dolphins have long, thin, curved teeth, but as they grow older, the teeth change into flat, square, bony disks.

This dolphin cannot see clearly because it lacks a special part in its eyes called a crystalline lens, so it is effectively blind. Instead, it uses a special sense called echolocation to find its way and hunt. Its body is brownish and sturdy in the middle, with a small triangular bump instead of a dorsal fin. The flippers and tail are thin and large compared to its body, which measures about 2–2.2 meters (6 ft 7 in – 7 ft 3 in) for males and 2.4–2.6 meters (7 ft 10 in – 8 ft 6 in) for females. The oldest known Indus river dolphin was a male that lived to be 28 years old and measured 199 centimeters (78 inches) long.

Distribution

The Indus river dolphin lives in the Indus River system. In the past, it could be found along a long stretch of the Indus River and its smaller rivers. Today, it is only found in a smaller part of the main river. A small group still lives in the Beas River and Harike Wetland in Punjab, India.

There are very few of these dolphins left. In 2017, scientists thought there were about 1,800 left. Numbers are still very low.

Behaviour and ecology

The Indus river dolphin is thought to swim on its side. This helps it move easily through shallow waters, especially when the water level is low.

Threats

The Indus river dolphin faces many challenges from human activities. Getting caught in fishing nets can hurt the dolphin population. Some dolphins are caught for their oil and meat.

Irrigation projects have lowered water levels, and water pollution from chemicals may also be affecting their numbers. Building dams on rivers separates dolphin groups and makes it harder for them to find mates. There are three groups of Indus river dolphins that might survive if protected. The group living in the Beas River is threatened by heavy fishing.

Conservation status

The Indus river dolphin is very rare and needs protection. It is listed as Endangered, which means there are not many left. Special rules help keep it safe, and scientists are studying it with satellites to learn more.