Amazon River Dolphin

Amazing Facts About the Amazon River Dolphin

Amazon river dolphins are also known as pink river dolphins or botos. They are a strong part of Amazon folklore; the locals typically respect and protect them. Some say that if a person drowns, their spirit enters the body of a boto, while others say river dolphins transform into beautiful people at night to lure humans into their river forever. The magical shape-shifters will always wear a white hat to hide their dolphin blowhole!

What do Amazon river dolphins look like?

Amazon river dolphins resemble other dolphins in body shape. Their dorsal fin is low and appears as a ridge along their backs, and their snouts are long and thin with bristles at the end, which they use to probe through the silt of the riverbed.

The skin of adult river dolphins is usually solid or patched pink. Colour varies with individuals, though, and it lightens with age. Males are pinker than females, and water temperature, clarity, and location may also affect colouring. Like other dolphin species, it is common for Amazon river dolphins to have scars over their bodies from interactions with other dolphins, boats or fishing hooks. Researchers can use these unique scar patterns to identify individual river dolphins, which is important for understanding populations and inputting conversation measures.

Amazon river dolphins have a large bump on their forehead known as a ‘melon’, which they use for navigating through the murky river waters using echolocation, just like bats!

How many subspecies are there?

There are two known subspecies of Amazon river dolphin. The common boto (Inia geoffrensis geoffrensis) is the largest. The Bolivian bufeo (I. g. boliviensis) is slightly smaller and ranges in colour from grey to bright pink.

Where do Amazon river dolphins live?

Unlike most dolphin species, Amazon river dolphins live in freshwater. They inhabit the Amazon and Orinoco river basins, including Brazil, Bolivia, Colombia, Ecuador, Peru, and Venezuela.

Populations are not thought to migrate, though individuals will move around their range with seasonal variations in water level. During the rainy season, large areas of the rainforest flood, and they swim between the submerged trees in search of prey. Studies have shown that females and their calves are more likely to spend time in lakes and small tributaries, while males remain in the main river channels. This may be a way to increase protection from predators and strong currents, or it may be that small fish are more abundant here.

What do Amazon River Dolphins eat?

Amazon river dolphins primarily eat fish, but they will occasionally tackle more difficult prey species such as river turtles and crabs. Unlike other toothed cetaceans (whales and dolphins), Amazon river dolphins have two types of teeth. The pointed front teeth help them to catch prey, while the back molars are for crushing and breaking food down.

The diet of Amazon river dolphins tends to vary more during the rainy season as fish spread across the floodplain and become harder to catch. Amazon river dolphins are active during both day and night and have even been seen hunting with Tucuxis and giant river otters. This is beneficial as they catch more fish together, but there is no squabbling for spoils as each species appears to prefer a different type of fish.

When do Amazon River Dolphins breed?

Amazon river dolphins give birth between May and July after 11 months of gestation (pregnancy). This is when river levels are highest and when prey populations are increasing.

Male amazon river dolphins are larger and pinker than females. They typically nibble the flippers of females to initiate courtship. They also use displays to attract a mate, including picking up water plants or pieces of wood in their mouths, twirling them in the air and smacking them onto the surface of the water. Males typically mate with multiple females, meaning that the strongest and most successful males will father more calves.

Mothers give birth to a single calf every 2-3 years. The bond between mother and calf is very strong, and it may take this long for the young river dolphin to develop all the skills it needs to survive on its own. Like other whale and dolphin species, the mum helps the newborn calf to the surface after birth so it can take its first breath of air!

What are the threats to the Amazon River Dolphin?

Thanks to their size, Amazon river dolphins have few natural predators, though caimans, jaguars and anacondas will hunt river dolphins on occasion. Humans are their biggest threat, with the local fishing industry and damage to the environment having the greatest impact.

Fishing

It can be hard to know how many Amazon river dolphins die because of fishing every year, as the bodies may be eaten by scavengers or taken by fishermen. However, the main threats from fishing include:

• Fishing nets: If dolphins get tangled in nets, they are unable to get to the surface to breathe.
• Hunting: Fishermen will sometimes kill dolphins if they see them as competition for fish. They may also deliberately kill them for bait, which they may then export to other countries.
• Explosives: While illegal in other countries, fishing with explosives still occurs in the Amazon Basin. Explosions kill any animals that are close by, and they may also interfere with the senses of dolphins by, for example, damaging their hearing.

Development

Human development is a major threat to Amazon river dolphins.

• Hydroelectric dams: Dams stop dolphins from moving around the Amazon Basin. And, as individuals get cut off from each other, they are unable to breed. This makes them venerable to local extinctions. Despite this, a 2014 report states that the Amazon Basin may become home to over 400 dams. This will lead to further habitat destruction as road access, and potential for development improves.
• Chemicals: Mercury from mining and chemical compounds from pesticides leach into the river. Once in the water, they make their way up the food chain and accumulate in dolphins and even transfer to their milk.  These chemicals are highly toxic, and the long-term effects are mostly unknown.
• Tourists and whale watching: With more and more people wanting to see dolphins, whale watching is on the rise. More and more boats are appearing on the river, which is increasing underwater noise. The risk of boat strikes is increasing, and people touching and feeding wild dolphins is a cause of stress for them.

How can you help the Amazon River Dolphin?

Amazon river dolphins spend much of their life hiding in the murky waters of the Amazon, so they are difficult to study. There is still a lot to learn, but improvements in satellite GPS technology are making it easier for scientists to monitor the health and movements of these elusive animals. This is important because, to be effective, conversation efforts need to be multinational. River dolphins cross borders, so studies need to look at the population as a whole.

Charities like Whale and Dolphin Conservation (WDC) are campaigning to establish protected areas of freshwater with management schemes in place that ensure a safe habitat for Amazon river dolphins. WDC is also working with local communities to reduce accidental dolphin deaths in fishing nets and to stop the deliberate killing of river dolphins for bait. Funding for their work comes largely from charity events, donations and their adoption schemes. Why not organise a fundraising event to spread the word about the plight of this little-known species?

Amazon River Dolphins act as indicators of the health of their rivers, meaning that their decline is an indicator of concern for the whole ecosystem. Attempts at maintaining captive populations of Amazon river dolphins have been largely unsuccessful – maintaining healthy wild populations in safe, protected habitats is the only way to ensure the survival of this beautiful species.

Page updated on 23/03/2023 by volunteer writer Ami Patrick.