The Ganges river dolphin (Platanista gangetica) is a type of freshwater dolphin that belongs to the Platanistidae family. It lives in the Ganges River and other connected rivers in South Asia, specifically in the countries of India, Nepal, and Bangladesh. This dolphin is closely related to the smaller Indus river dolphin, which lives in the rivers of the Indus Basin in Pakistan and northwestern India.
The Ganges river dolphin is also called "susu" in some areas. In Assam, it is known as "shihu" (Assamese: শিহু). In West Bengal and Bangladesh, it is referred to as "shushuk" (Bengali: শুশুক). In the Chittagong region, it is called "Uttum" (Chittagonian: উত্তুম). The Government of India has recognized the Ganges river dolphin as its National Aquatic Animal. It is also the official animal of the Indian city of Guwahati. The first recorded sighting of this dolphin in the Hooghly River was made by William Roxburgh.
Description
The Ganges river dolphin has a ridge-shaped back fin and females are generally larger than males. These dolphins are usually tan, chocolate brown, dark grey, or light blue in color. They have a long, narrow snout with sharp, pointed teeth, similar to other river dolphins. Their body shape is rounded in the belly area, which, along with their rectangular back fin, makes them appear stocky compared to other dolphin species. Their flippers and tail flukes are large and wide. They have a large, rounded head used for echolocation, as they have poor eyesight. Their eyes are small because the water they live in is cloudy. Ganges river dolphins typically measure between 2.2 and 2.6 meters (7 to 8 feet) in length. The oldest recorded dolphin was a male that was 28 years old and measured 199 centimeters in length. Scientists estimate that these dolphins can live up to 30 years.
Taxonomy
The Ganges river dolphin separated from the Indus river dolphin during the Pleistocene, about 550,000 years ago. The oldest fossil found that belongs to this species is 12,000 years old.
The Ganges river dolphin was officially named Delphinus gangeticus twice in 1801 by Heinrich Julius Lebeck and William Roxburgh. Both scientists likely used the same type specimen, a dolphin caught near Calcutta in late 1797 and sent to the Hunterian Museum in London. This specimen may have been destroyed during World War II, but models of its snout and part of its lower jaw were made and are now kept at the Natural History Museum. Historians have debated whether Lebeck or Roxburgh should be credited with the name. Research by Kinze (2000) showed that Lebeck’s description was published on August 24, while Roxburgh’s was likely published no earlier than September, giving Lebeck priority. Elisha Gray later named the species Platanista gangetica in 1835.
This species and the Indus river dolphin were once considered the same species, Platanista gangetica. However, in the 1970s, scientists separated them into two distinct species. In the 1990s, they were again grouped as one species. More recent studies of genetic differences, timing of divergence, and skull structure now support that they are separate species.
Etymology
The species has several common names in different regions. It is commonly called "susu" in some areas. In Hindi, it is known as "soons," "soans," or "soos." In Bengali, it is called "shushuk." In Assamese, it is referred to as "hiho" or "hihu." In Nepali, it is known as "shus" or "suongsu." In some regions, it is named after a character from Hindu mythology called "bhagirath." In ancient Sanskrit texts, it was probably called "shishumar." During the Mughal era, it was referred to as "pani suar."
Distribution
The Ganges river dolphin is found in the Ganges-Brahmaputra-Meghna and Karnaphuli-Sangu river systems of Bangladesh and India, as well as the Sapta Koshi and Karnali Rivers in Nepal. These dolphins prefer deep pools and areas with slow-moving water currents near river bends, midchannel islands, and where rivers join together.
A 2025 survey counted 6,324 Ganges river dolphins in India. Of these, 3,275 lived in the main part of the Ganges River, and 2,414 lived in its smaller tributaries. In the Brahmaputra River, 584 dolphins were found in the main river, and 51 lived in its tributaries.
Behaviour
The Ganges river dolphins often swim alone or in pairs. They rarely jump out of the water and are shy around boats, making them hard to see.
This species avoids objects in both the very murky water of its habitat and in clear water when kept in captivity. This suggests the dolphins can use echolocation to move around and find food. There is not much known about how often they use sounds to communicate with each other. They can make whistles, but they do so very rarely, which means whistles are likely not used for communication. Instead, the dolphins most often use echolocation sounds, such as clicks, bursts, and twitters. These sounds are similar in shape and frequency to the echolocation patterns of the Amazon river dolphin. Both species regularly produce sounds below 15 kHz, and the highest sounds they make are likely between 15 and 60 kHz.
Echolocation is also used to count dolphin populations through acoustic surveys. This method is still being improved and is not widely used because of high costs and the need for technical skills. Since the dolphins are blind, they make ultrasonic sounds that bounce off other fish and water animals, helping them find prey.
The Ganges river dolphin does not have a specific time of year for mating. A calf is born about 8 to 12 months after conception and stays with its mother for one year.
The Ganges river dolphin uses echolocation to find food. It eats crustaceans like prawns and fish such as carp, mahseer, and even sharks like the Ganges shark (Glyphis gangeticus). It also eats birds and turtles.
Threats
The Ganges river dolphin has been listed as an Endangered species on the IUCN Red List since 1996. It faces threats from habitat fragmentation caused by reduced dry-season river flows, entanglement in fishing nets, accidental deaths from fishing activities, targeted hunting, and pollution in rivers near cities and farmland. The dolphin is also disturbed by inland boat traffic and may be harmed by seismic surveys, oil well accidents, and changes in river patterns due to climate change. Human activities have reduced the dolphin’s natural habitat and population because of noise from boats, fishing bycatch, and the construction of dams and hydroelectric plants. Pollution and overfishing for oil also threaten the species. Getting caught in fishing nets can harm dolphin populations, and some individuals are hunted each year. Their oil and meat are used as medicine, to increase sexual desire, and as bait for catfish. Industrial and agricultural chemicals may have contributed to population decline because these chemicals build up in the dolphins’ bodies. In the National Chambal Sanctuary, a major danger is the river becoming shallower and sandbars forming, which splits the river into smaller sections.
Conservation
The Ganges river dolphin is protected from international trade because it is listed in Appendix I of the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES). This means that buying and selling the dolphin across countries is not allowed. In Uttar Pradesh, the government is sharing ancient Hindu texts to get more community support for protecting the dolphin. One line from Valimiki's Ramayana describes how the Ganges River came from Shiva's hair, and with this water came many living things, including animals, fish, and the Shishumaar, which is the dolphin.
On May 20, 2013, India's Ministry of Environment and Forests said that dolphins have the legal rights of nonhuman persons. This means that keeping dolphins in captivity for entertainment is not allowed. If dolphins are kept in captivity, it must meet certain legal requirements.
On December 31, 2020, a dead adult dolphin was found in the Sharda Canal in Pratapgarh district, India. A video shared online showed a group of men hitting the dolphin with sticks and an axe. On January 7, 2021, three people were arrested for this act. In another case, some fishermen caught a Gangetic dolphin and ate it, which led to their arrest by police in Kaushambhi, Uttar Pradesh.
Bangladesh has created six protected areas in the Sundarbans.
On August 15, 2020, which was India's 74th Independence Day, the Indian Ministry of Environment, Forest and Climate Change announced "Project Dolphin" to help protect both river and ocean dolphins.
In culture
The Ganges dolphin is connected to Ganga and is sometimes shown as her vehicle, the makara.