The pink river dolphin, or Amazon river dolphin, lives only in fresh water in the Amazon and Orinoco river basins of South America. Young ones are grey and turn pink as adults. It has a bendy neck for twisting through flooded forests, finds fish by echolocation, and is listed by WWF as Endangered.
pink river dolphins quick facts
- Pink river dolphins are born dark grey and turn pink as they grow up.
- None of the bones in their necks are joined, so they can turn their heads in all directions.
- They swim into flooded forests in the wet season.
- Scientists have found at least 43 kinds of fish in their diet.
- They normally swim at 1.5 to 3.2 km/h, slower than a person walks.
What is a pink river dolphin?
The pink river dolphin is a dolphin that lives only in fresh water, in the rivers and lakes of South America. Its proper name is the Amazon river dolphin, and it is also called the boto. Its scientific name is Inia geoffrensis.
It lives throughout much of the Amazon and Orinoco river basins, in seven countries: Bolivia, Brazil, Colombia, Ecuador, Guyana, Peru and Venezuela. It is also found in the Tocantins-Araguaia river basin in Brazil.
Like all dolphins, it is a mammal, not a fish. It breathes air through a blowhole, gives birth to live young, and feeds its babies milk.
Why is it pink?
Here is something that surprises many people. Not every pink river dolphin is pink.
Young ones are dark grey. As they grow up, adults turn pink, either all over or in blotches. Males are usually more brightly coloured than females.
How pink a dolphin looks can also depend on the temperature and clearness of the water, and on where it lives. So two adult dolphins from different rivers can look quite different.
How big is a pink river dolphin?
WWF says Amazon river dolphins can grow up to 9.2 feet (2.8 m) long and weigh up to 352 pounds (160 kg). That is longer than a tall adult lying down, and heavier than two grown men.
Most are smaller than that. In one set of measurements, males averaged about 2.3 m (7.6 feet) long and 154 kg, and females about 2 m (6.6 feet) and 100 kg. So males are usually bigger than females.
A dolphin with a bendy neck
Most dolphins cannot turn their heads very far. The Amazon river dolphin can.
None of the bones in its neck are joined together. That means it can move its head in all directions, turning it as much as 180 degrees, a bit like you can turn and nod yours.
A bendy neck is very useful where it lives. It lets the dolphin twist and turn as it hunts among tree roots, branches and plants under the water.
Swimming through a forest
For part of each year, heavy rain makes the rivers of the Amazon River rise and spill out over the land. Large areas of forest end up standing in water.
Amazon river dolphins live in main rivers, small channels, river mouths and lakes. In the wet season, they swim right into this flooded forest, weaving between the trunks of trees.
Imagine looking out of a boat and seeing a pink dolphin swim past a tree. In the Amazon rainforest, that really happens.
Where Pink River Dolphins Live
- The Amazon and Orinoco — The two big river basins they live in
- Seven countries — Bolivia, Brazil, Colombia, Ecuador, Guyana, Peru and Venezuela
- The Tocantins-Araguaia — Another river basin in Brazil where they are found
- Flooded forest — Where they swim in the wet season
- Boto — Another name for the Amazon river dolphin
Finding food with sound
The rivers of the Amazon are often murky, so the dolphins cannot always see far. Instead, they find their way using sound. This is called echolocation.
A river dolphin makes clicking sounds and listens for the echoes that bounce back. The echoes tell it where fish, rocks and branches are, even when it cannot see them.
Its clicks range from 16 to 170 kilohertz. Most of them are far too high-pitched for people to hear. The loudest part of the sound is usually around 45 kilohertz.
What do pink river dolphins eat?
Mostly fish. Scientists who studied what river dolphins had eaten found at least 43 kinds of fish, from 19 different fish families. Some were only 5 cm long, and others were as long as 80 cm.
That is a very varied menu. River dolphins also eat turtles, shrimps and crabs. A single river dolphin’s stomach may hold more kinds of fish than some other dolphins eat altogether.
A river dolphin eats about 2.5% of its body weight every day. For a 100 kg dolphin, that is about 2.5 kg of fish.
Teeth for grabbing and crushing
Many dolphins have teeth that all look alike. The Amazon river dolphin has two kinds.
The teeth at the front of its long beak are cone-shaped, good for grabbing slippery fish. The teeth at the back have ridges, called flanges, which can crush.
Those back teeth let it crunch through prey with hard, armoured bodies, which a dolphin with only pointed teeth would find much harder to eat. It is the only dolphin with anything like the molars, or grinding teeth, at the back of your own mouth.
Hunting in Murky Water
- Echolocation — Finding things by listening to the echoes of clicks
- About 45 kilohertz — The loudest part of a river dolphin's clicks
- Cone-shaped front teeth — Good for grabbing slippery fish
- Ridged back teeth — Can crush prey with hard bodies
- The only dolphin with molar-like teeth — The Amazon river dolphin
How pink river dolphins live
Amazon river dolphins are not speedy. They normally swim at about 1.5 to 3.2 km/h, which is slower than a person walks. When they need to, they can put on bursts of speed of 14 to 22 km/h.
They are usually seen alone, as a mother with her calf, or in small groups. Sometimes they gather in loose groups to feed or to find a mate.
They can be curious and playful, too. People have seen them rub against canoes and grab hold of canoe paddles.
They are natural gymnasts, too. River dolphins often pivot on the spot, swim backwards and even swim upside down, something few other dolphins do so easily.
Baby river dolphins
A mother has one calf at a time. It is about 80 cm long when it is born.
She feeds it milk for well over a year, and she usually has a new calf every two to three years. In captivity, calves have been measured growing about 21 cm a year.
River dolphins do not do well in captivity. Some have lived 10 to 26 years there, but one report found that captive botos lived only about 33 months on average.
River Dolphin by Numbers
- Up to 2.8 m — How long the biggest Amazon river dolphins grow
- At least 43 — Kinds of fish found in river dolphins' diet
- About 2.5% — How much of its body weight a river dolphin eats each day
- About 80 cm — How long a calf is when it is born
- 1.5 to 3.2 km/h — How fast they normally swim
Legends of the boto
People who live along the Amazon have told stories about pink river dolphins for a very long time. The dolphins play an important part in local beliefs.
In some legends, a dolphin can turn itself into a man. In others, dolphins carry swimmers away to Encante, a magical city hidden under the water.
Stories like these show how closely people and dolphins have shared the rivers, and how special the boto is to the people who live beside it.
Why are pink river dolphins in danger?
WWF lists the Amazon river dolphin as Endangered. There are thought to be tens of thousands left, but they face many threats.
Dams are one. They split rivers into sections and cut groups of dolphins off from each other.
Pollution is another. In Bolivia, small-scale gold mining puts mercury into the rivers. The mercury builds up in catfish, which feed on the river bottom, and the dolphins eat the catfish.
Some fishermen see the dolphins as rivals for fish. Dolphins can be hurt in fishing gear, and some are killed on purpose. In parts of Brazil and Colombia, dolphins have been killed to use as bait for a kind of catfish that sells for a high price.
Cutting down the forest harms them as well, because it reduces the fish they eat. Careless tourism and new water projects, such as dams and canals, add to the pressure. In one area scientists have studied, the number of river dolphins is thought to be halving every ten years. WWF supports surveys to count river dolphins, and research into how dams affect them.
Three things people get wrong
Not all pink river dolphins are pink. Young ones are dark grey, and adults can be anything from blotchy to bright pink.
Pink river dolphins do not live in the sea. They live only in fresh water, in the Amazon and Orinoco river basins.
They are not fast, sleek swimmers. They usually move slower than walking pace, and their bendy necks are made for twisting through flooded forests, not racing.
Did you know? Amazon river dolphins have two kinds of teeth: cone-shaped ones at the front for grabbing, and ridged ones at the back for crushing armoured prey.
Pink River Dolphins: Fact or Myth?
- Pink river dolphins live in the sea.
- Male river dolphins are usually more brightly coloured than females.
- Pink river dolphins are very fast swimmers.
- River dolphins can swim backwards and upside down.
- Pink river dolphins are fish.
- River dolphins sometimes eat river turtles and crabs.
- Pink river dolphins always live in big herds.
- WWF lists the Amazon river dolphin as Endangered.
Try it
Close your eyes and ask a friend to clap from different spots in the room. Point to where each clap came from. River dolphins use echoes of their own clicks in a similar way to find fish in murky water.
Knowledge check
Why can a pink river dolphin turn its head in all directions?
Show answer
Because none of the bones in its neck are joined together.
What colour are young pink river dolphins?
Show answer
Dark grey. They turn pink as they grow up.
Frequently asked questions
Why are Amazon river dolphins pink?
Amazon river dolphins are born dark grey and turn pink as they grow up. Males are usually pinker than females, and the shade can depend on water temperature, water clearness and where the dolphin lives.
Where do pink river dolphins live?
Pink river dolphins live only in fresh water, in the Amazon and Orinoco river basins of Bolivia, Brazil, Colombia, Ecuador, Guyana, Peru and Venezuela. In the wet season they swim into flooded forests.
How big do pink river dolphins get?
Amazon river dolphins can grow up to 9.2 feet (2.8 m) long and weigh up to 352 pounds (160 kg), according to WWF. Males are usually bigger than females.
What do pink river dolphins eat?
Pink river dolphins eat mostly fish, at least 43 kinds from 19 fish families. They eat about 2.5% of their body weight every day and use echolocation to find prey in murky water.
Are pink river dolphins endangered?
Yes. WWF lists the Amazon river dolphin as Endangered. Threats include dams, mercury pollution from gold mining, fishing gear, deliberate killing for bait and the loss of forest.
Can pink river dolphins turn their heads?
Yes. None of the neck bones of an Amazon river dolphin are joined together, so it can move its head in all directions. This helps it hunt among tree roots and branches in flooded forests.
Sources
- WWF: Amazon river dolphin — range, population, size, status and threats including dams, mercury and bait fishing
- Animal Diversity Web, University of Michigan: Inia geoffrensis — colour changes, size, neck, habitat, echolocation, teeth, diet, behaviour, calves and lifespan
- River Dolphins (WWF and partners): Amazon river dolphin — range, colour, neck, teeth, diet, behaviour, legends, threats and population decline
Pink River Dolphin Final Challenge
- Why are river dolphins killed in parts of Brazil and Colombia?
- How does mercury get into rivers in Bolivia?
- What is happening to river dolphin numbers in one area scientists have studied?
- How do dams harm river dolphins?
- In some legends, where can a dolphin carry a swimmer away to?
- About how much do calves grow each year in captivity?
- What have people seen curious river dolphins do?
