River Dolphin

The Amazon pink river dolphin is the biggest and smartest animal of the four freshwater dolphin species.

The Amazon river dolphin is a freshwater animal. It lives in the Amazon and the Orinoco rivers as well as in waterways located in Bolivia, Columbia and Peru. The river dolphin is smaller than other types of saltwater dolphins, and the species has excellent hearing. These dolphins must live in warm, shallow water areas because they have very little blubber. River dolphins suffer in captivity with few aquariums able to keep them alive.
 

5 Incredible River Dolphin Facts

• Male river dolphins are occasionally pink
• River dolphins have more brain capacity than humans
• They have human-like teeth
• River dolphins live in warm waters
• Unlike ocean dwelling dolpins, river dolphins have a hump instead of a dorsal fin 
 

River Dolphin Scientific Name

The Amazon river dolphin is also called a boto or the pink river dolphin, and its scientific name is Inia Geoffrensis. Other freshwater types are the Yangtze river dolphin, the Ganges river dolphin and the Indus river dolphin. Freshwater dolphins belong to the Mammalia class. There are four river dolphin families, which include the Iniidae, Pontoporiidae, Lipotidae and Platanistoidea.

The animal’s common name comes from where it often makes its home and its skin color. The name boto is the one used by the natives. It is also a popular character in South American mythology. In legends, the animals have amazing musical skills and are seductive. They also love parties. Some myths claim that the dolphins can shapeshift into human form and have magical abilities.
 

River Dolphin Appearance and Behavior

The pink river dolphin features that distinctive dolphin smile. They have rounded foreheads and long, slender beaks. Male river dolphins are sometimes pink. The pink coloring occurs becaue as dolphins age their skin becomes translucent, or clear, allowing the blood to show through. This is very similar to the pink fairy armadilo, whose pink hue is caused by the same effect. 

Female river dolphins are larger than the males. The animal has conical-shaped teeth that they use to catch small fish and other prey. The river dolphin features a long nose that can measure up to 23 inches long, and this is about four times longer than the nose of ocean dolphins. The river dolphin has a two-chambered stomach, and they breath by emitting air through a blowhole.

Of the four river dolphin species pink river dolphins are the largest, growing as long as 8 feet and weighing around 450 pounds, which is about the same weight as a welsh pony. This type of dolphin doesn’t have a dorsal fin. Instead, it sports a modified hump. The animal makes its way through rivers using strong flippers and a tail fluke. Compared to oceanic dolphins, river dolphins swim slowly. Their top speed is around 35 miles per hour. The reason for this is that their neck vertebrae are not fused. This gives them more flexibility, but it means that they can’t swim as fast. River dolphins are able to turn their heads without shifting their bodies.

The animals swim with great precision. Because river dolphins are extremely flexible, they can maneuver around rocks, tree trunks and other objects. They also have the ability to swim forward using one flipper while the other flipper paddles backward. This swimming method lets them make tight turns. River dolphins also like to swim upside down.

River dolphins have exceptionally large brains, and while dolphins are known for swimming in groups, river dolphins tend to spend more time alone or among small groups of two to four dolphins. You might see a bigger group of them in areas that are rich with food, but it’s less common with river dolphins.

Like their ocean cousins, pink river dolphins are friendly and curious. They interact with humans frequently. River dolphins have unique ear adaptions to help them survive in their watery environment. Dolphins hear sound from their throats instead of from their outer ear to their inner ear. The animal’s ear is also acoustically separated from its head. Separating these two body parts are sinus pockets. The combination gives the animal enhanced directional hearing under the water. Dolphins use an organ called a melon to emit high frequency clicks. This allows them to produce bio sonar. They use it to orient themselves.

Dolphins are reliant on echolocation. The animal species uses echolocation so well that a river dolphin could survive even if it were blind. Echolocation lets the animal determine the size and shape of any surrounding item or object. River dolphins have small eyes, and they are unable to see well. Also, their eyes are on the sides of their heads. This means that their vision features two separate views instead of the forward view that people see.

Researchers believe that some types of river dolphins are blind while others just have extremely poor eyesight. A number of the animals are killed because they inadvertently come into contact with nets and fishing boats.
 

River Dolphin Habitat

River dolphins live in freshwater areas including lakes, enormous rivers and small tributaries. You’ll find them in Bolivia, Columbia, Ecuador, Brazil, Venezuela and Peru. The animals live in the Amazon and Orinoco riverways and in the Araguaia River.
 

River Dolphin Diet

Amazon River dolphins have teeth that are similar to the molar teeth that humans have. Like people, the animals use their teeth to break up food before swallowing it. River dolphins aren’t picky about what they eat. The mammals will dine on turtles, shrimp, crabs and more than 40 different species of fish including piranhas.
 

River Dolphin Predators and Threats

Animals that prey on the river dolphin include large snakes, jaguars and caimans. Human development and farming have had a major impact on the habitats of the river dolphin. These activities have impacted the ecology of the waterways. Human fishing is also threatening the species. Overfishing is a problem because it decreases the animal’s food supply. The dolphins also get caught in the nets.

Pollution is another threat to the Amazon river dolphin. Small gold mining operations cause mercury pollution, and this makes its way to dolphins through the food chain. River dolphins eat a lot of catfish, which dwell on the bottom of waterways where mercury generally accumulates.

River dolphins are endangered. The Brazilian Institute of Environment and Renewable Natural Resources has taken steps to protect the dolphin species. They’ve made it illegal for fishermen to kill the dolphins. 
 

River Dolphin Reproduction, Babies and Lifespan

In South America, spring is the rainy season. During this time, acres and acres of rainforest floods, turning into an enormous tree-covered sea. The water becomes deep enough for the river dolphins to swim amongst the trees. Mating season occurs when the water recedes, and the male and female dolphins are constricted to the river channels. The dolphin species is polygamous, meaning males mate with several females each year. However, females don’t mate every year. They mate every two to three years.

Female river dolphins are more attracted to males that are a brighter shade of pink. To impress the females, male river dolphins smack the water with bunches of grasses or branches in their mouths. Sometimes, they hold up a turtle to capture the attention of a female. When a female river dolphin becomes pregnant, she’ll carry the calf for 11 to 15 months. The animal species gives birth to just one calf. After a baby dolphin is born, it will nurse for over a year. Baby dolphins are often around 30 inches long, and they weigh around 22 pounds. Adult female dolphins usually have their calves from July to September. Once they’re born, babies remain close to their mothers for protection.

Sexual maturity is based on the dolphin’s size. When a female reaches 5.5 feet in length, she becomes sexually mature. Males reach the stage once they’re 7 feet long. In the wild, river dolphins live for an average of 12 to 18 years, but they can live for as long as 30 years.

 

River Dolphin Population

The estimated river dolphin population is in the tens of thousands when the four freshwater species are counted together. However, river dolphins are under threat. For instance, the Araguaian river dolphin population is from 600 to 1,500 animals. Humans are the cause of population endangerment of the South Asian river dolphins. Irrigation in the river systems there has decreased the water levels. The water supply is also polluted, which is causing a population decline.

The Chinese river dolphin, also called Baiji, used to live in China’s Yangtze River, but researchers have reported that it became extinct during 2006.
 

River Dolphin FAQ

Are River Dolphins Carnivores, Herbivores or Omnivores?

Amazon river dolphins are carnivores. They only eat meat.
 

Are River Dolphins Dangerous to Humans

Most of the time, dolphins are not dangerous to humans. In fact, the animals are super curious, friendly and generally approachable. They often have fun with humans by teasing them and seeking their attention. There are even accounts of the species protecting people from sharks or helping a lost person make his or her way back to land.

The only time that dolphins are likely to harm humans is if they are agitated or provoked. If you come across a river dolphin and want to feed him or her, keep in mind that it might be prohibited.
 

How Do Dolphins Sleep?

Most dolphin species sleep by resting one hemisphere of their brain in what’s called slow-wave sleep. During this state, they stay alert enough to keep breathing and look out for predators. The Indus river dolphin sleeps differently. Since the animal lives in waters with powerful currents and a great deal of floating debris, the dolphin must stay alert to avoid becoming injured. To stay safe, the dolphin sleeps in short four to 60 second spurts.

 

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Sources:
1. David Burnie, Dorling Kindersley (2011) Animal, The Definitive Visual Guide To The World's Wildlife
2. Tom Jackson, Lorenz Books (2007) The World Encyclopedia Of Animals
3. David Burnie, Kingfisher (2011) The Kingfisher Animal Encyclopedia
4. Richard Mackay, University of California Press (2009) The Atlas Of Endangered Species
5. David Burnie, Dorling Kindersley (2008) Illustrated Encyclopedia Of Animals
6. Dorling Kindersley (2006) Dorling Kindersley Encyclopedia Of Animals
7. David W. Macdonald, Oxford University Press (2010) The Encyclopedia Of Mammals