What is a river dolphin?

River dolphins are any of six species of small, primarily freshwater aquatic mammals related to whales. They possess elongated beaks and rounded foreheads, setting them apart from familiar dolphins like the bottlenose. These dolphins inhabit rivers in South America and south-central Asia. Less athletic than their marine counterparts, river dolphins spend their time near river bottoms, using their sensitive snouts to search for fish and crustaceans. Their exceptional sonar helps them navigate murky waters with ease. The Ganges and Indus river dolphins are endangered due to industrial river traffic and hunting. The IUCN classifies the Atlantic humpbacked dolphin as critically endangered.

Where do river dolphins live?

River dolphins inhabit rivers and coastal waters across South America and Asia. Specifically, they are found in the Amazon and Orinoco river basins, as well as the coastal waters of Brazil, Argentina, and Uruguay. Several species are native to the Ganges, Brahmaputra, Karnaphuli, and Meghna rivers in India, Bangladesh, Nepal, and Bhutan. The Chinese river dolphin, or baiji, was native to China’s Yangtze River but is now considered functionally extinct. Though most river dolphins live in fresh water, some reside in coastal waters.

How are river dolphins different from ocean dolphins?

River dolphins and ocean dolphins, both toothed whales, have distinct characteristics and habitats. River dolphins comprise the families Platanistidae and Iniidae , while ocean dolphins belong to the family Delphinidae . River dolphins inhabit freshwater rivers in South America and Asia, whereas ocean dolphins live in marine environments worldwide, from equatorial to subpolar waters, with some venturing into major river systems. River dolphins have long beaks and rounded foreheads and navigate muddy waters with exceptional sonar, while ocean dolphins have beaklike snouts and simple, needlelike teeth.

What do river dolphins eat?

River dolphins are carnivores that eat fish, crustaceans, and invertebrates. Ganges river dolphins often swim on their sides, using their flippers to probe the river bottom for fish, shrimp, and mollusks. Amazon river dolphins consume a diet of various fish and crustaceans.

Why are river dolphins endangered?

River dolphins are endangered due to several factors, including transportation and dams that fragment their habitat. Other threats include heavy industrial river traffic and hunting. Dams also restrict migration, further endangering these species. Several dolphin species are at risk, with the Ganges river dolphin and the Indus river dolphin classified as endangered. The Chinese river dolphin is now believed to be functionally extinct.

How do scientists help protect river dolphins?

Several dolphin species are at risk of extinction. The Ganges river dolphin and the Indus river dolphin are classified as endangered species. There may be fewer than 1,000 Ganges river dolphins left. They face a range of threats, particularly in India and Pakistan, where rivers are heavily used for transportation and where numerous dams have fragmented their habitat.

river dolphin

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An illustration of a Ganges River dolphin (Platanista gangetica) showing its elongated snout and flippers, with a faint scuba diver silhouette below for size comparison. Measurement bars indicate the dolphin is about 2.5 meters (8.2 feet) long.

Map of northern South America showing the distribution ranges of three river dolphin species. The Amazon River dolphin range is shaded green, covering much of the Amazon basin across Brazil, Peru, Ecuador, and Colombia. The Orinoco River dolphin range is shown in yellow, limited to the Orinoco basin in Venezuela and Colombia. The Bolivian river dolphin range is marked in purple within central Bolivia. The Araguaian boto's range is shown in orange along the Araguaia and Tocantins rivers in Brazil

A pink Amazon river dolphin, Inia geoffrensis, partially submerged in murky water, showing its elongated snout and rounded forehead.

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Related Topics:: dolphin; toothed whale; Platanista; Iniidae; Atlantic humpbacked dolphin

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river dolphin

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Top Questions

What is a river dolphin?
River dolphins are any of six species of small, primarily freshwater aquatic mammals related to whales. They possess elongated beaks and rounded foreheads, setting them apart from familiar dolphins like the bottlenose.

These dolphins inhabit rivers in South America and south-central Asia. Less athletic than their marine counterparts, river dolphins spend their time near river bottoms, using their sensitive snouts to search for fish and crustaceans. Their exceptional sonar helps them navigate murky waters with ease.

The Ganges and Indus river dolphins are endangered due to industrial river traffic and hunting. The IUCN classifies the Atlantic humpbacked dolphin as critically endangered.
3 Britannica Sources
Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.
Where do river dolphins live?
River dolphins inhabit rivers and coastal waters across South America and Asia. Specifically, they are found in the Amazon and Orinoco river basins, as well as the coastal waters of Brazil, Argentina, and Uruguay. Several species are native to the Ganges, Brahmaputra, Karnaphuli, and Meghna rivers in India, Bangladesh, Nepal, and Bhutan. The Chinese river dolphin, or baiji, was native to China’s Yangtze River but is now considered functionally extinct. Though most river dolphins live in fresh water, some reside in coastal waters.
3 Britannica Sources
Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.
How are river dolphins different from ocean dolphins?
River dolphins and ocean dolphins, both toothed whales, have distinct characteristics and habitats. River dolphins comprise the families Platanistidae and Iniidae, while ocean dolphins belong to the family Delphinidae. River dolphins inhabit freshwater rivers in South America and Asia, whereas ocean dolphins live in marine environments worldwide, from equatorial to subpolar waters, with some venturing into major river systems. River dolphins have long beaks and rounded foreheads and navigate muddy waters with exceptional sonar, while ocean dolphins have beaklike snouts and simple, needlelike teeth.
3 Britannica Sources
Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.
What do river dolphins eat?
River dolphins are carnivores that eat fish, crustaceans, and invertebrates. Ganges river dolphins often swim on their sides, using their flippers to probe the river bottom for fish, shrimp, and mollusks. Amazon river dolphins consume a diet of various fish and crustaceans.
5 Britannica Sources
Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.
Why are river dolphins endangered?
River dolphins are endangered due to several factors, including transportation and dams that fragment their habitat. Other threats include heavy industrial river traffic and hunting. Dams also restrict migration, further endangering these species.

Several dolphin species are at risk, with the Ganges river dolphin and the Indus river dolphin classified as endangered. The Chinese river dolphin is now believed to be functionally extinct.
4 Britannica Sources
Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.
How do scientists help protect river dolphins?
Several dolphin species are at risk of extinction. The Ganges river dolphin and the Indus river dolphin are classified as endangered species. There may be fewer than 1,000 Ganges river dolphins left. They face a range of threats, particularly in India and Pakistan, where rivers are heavily used for transportation and where numerous dams have fragmented their habitat.
2 Britannica Sources
1. dolphin: Conservation status
2. A Dose of Dolphin-Induced Dopamine: 8 Species of Adorable Cetacean: Ganges river dolphin
Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.

South American river dolphinMap of the geographic home ranges of three South American river dolphin species.

river dolphin, any of six species of small, usually freshwater aquatic mammals that are related to whales (order Cetacea). These dolphins are found in rivers of south-central Asia, China, and South America and in the coastal waters of Brazil, Argentina, and Uruguay. River dolphins have long beaks and rounded foreheads, distinguishing them from more familiar-looking dolphins such as the bottlenose dolphin of the family Delphinidae. The ancestors of river dolphins were marine dolphins that invaded freshwater environments during high sea levels occurring near the end of the Miocene Epoch (23 million to 5.3 million years ago). Indian river dolphins (Platanista) are part of the family Platanistidae, whereas the genera Inia, Lipotes, and Pontoporia make up the family Iniidae.

Less athletic than most other dolphins, river dolphins do not make sensational leaps and dives. Instead, they spend much of their time at river bottoms, probing with sensitive snouts for mud-loving fish and crustaceans. Despite having small eyes (Ganges and Indus river dolphins’ eyes even lack a lens), river dolphins navigate muddy waters with ease thanks to exquisite sonar—perhaps the best among all the cetaceans. They are often friendly and curious toward people.

The largest species is the Amazon river dolphin (Inia geoffrensis). Also called boto, bufeo, and pink dolphin, it is common in the turbid waters of the Amazon and Orinoco river basins. A male Amazon river dolphin can grow to over 2.4 metres (8 feet) and 160 kg (350 pounds); females are slightly smaller. Its colour can vary from dark gray to mottled pink-and-gray to bright pink. The young are gray. Corpulent but extremely flexible, this dolphin navigates with the grace of a flying bird among the branches of submerged trees when annual rains flood the forest. Amazon river dolphins are usually seen in groups. They often swim and play with another small dolphin, the tucuxi (Sotalia fluviatilis), which is found in both fresh and marine waters and is not classed with river dolphins. In some parts of the Amazon, river dolphins will herd fish into fishermen’s nets; in other areas, they will raid the nets instead.

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The Araguaian boto (I. araguaiaensis), which is physically similar to the Amazon river dolphin, was classified as a separate species in 2014 on the basis of its distinct DNA. This species inhabits the Araguaia-Tocantins river system in Brazil.

The Bolivian river dolphin (I. boliviensis), native to a few remote streams in the Bolivian Amazon, is slightly smaller than the Amazon river dolphin, and its skin is coloured grayish pink. The Teotônio rapids between Bolivia and Brazil separate the two species, and DNA studies suggest that neither competition nor interbreeding has occurred between the Bolivian river dolphin and the boto for many tens (or possibly hundreds) of thousands of years. Population estimates suggest that the species may contain as many as 25,000 individuals.

The smallest river dolphin species, the La Plata river dolphin (Pontoporia blainvillei), also lives in South America. Also known as the franciscana, it inhabits the coastal waters of Brazil, Uruguay, and Argentina. Gray above and pale below, this little dolphin grows only 1.2–1.7 metres (4–5.6 feet) long and weighs 20–60 kg (45–135 pounds). Females are larger than males.

The Ganges river dolphin, or susu (Platanista gangetica), inhabits the Ganges, Brahmaputra, Karnaphuli, and Meghna rivers and their tributaries in India, Bangladesh, Nepal, and Bhutan. Adults can be nearly 3 metres (10 feet) long. This dark-coloured dolphin frequently swims on its side, trailing a flipper to probe the bottom for fish, shrimp, and mollusks. Its close relative, Platanista minor (Indus river dolphin, bulhan, and Indus susu), is sometimes classified with P. gangetica as a subspecies and is found only in Pakistan. Both species are endangered because of heavy industrial river traffic, hunting for meat and oil, and construction of dams that restrict migration.

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The baiji, or Chinese river dolphin (Lipotes vexillifer), was native to China’s Yangtze River. Pale blue-gray above and lighter below, it grew to 2.4 metres (8 feet). As the waters of the Yangtze grew more crowded and polluted, the baiji became the world’s most endangered cetacean. Despite reports of an encounter with this river dolphin in 2007, the last confirmed sighting occurred in 2002. Although the International Union for Conservation of Nature and Natural Resources (IUCN) considers the species to be critically endangered, it is now widely believed to be functionally extinct.

In addition, the Atlantic humpback dolphin (Sousa teuszii, family Delphinidae), which is also widely known as the Cameroon river dolphin, is a marine species that also inhabits rivers, estuaries, and nearshore waters along the African coast between southern Morocco and southern Angola. The IUCN classified the Atlantic humpback dolphin as a vulnerable species between 2008 and 2017 but reclassified the species as critically endangered in 2017 after studies suggested that fewer than 3,000 remained in the wild.

The Editors of Encyclopaedia Britannica This article was most recently revised and updated by John P. Rafferty.

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