40 Fun Facts About Amazon River Dolphin

Amazon river dolphins turn pinker with age; what is believed to give adult males their rosy colour?

Scar tissue builds up over years of fights and rough play, so battle-worn males end up the pinkest. Females are thought to prefer the brighter ones.

In Amazon folklore, a river dolphin comes ashore at night as a charming man wearing what to hide his blowhole?

A hat covers the one feature the shapeshifter cannot change. In the tales he loves a party, then hurries back to the water by morning to become a dolphin again.

Which part of the Amazon river dolphin's body bends unusually far because its vertebrae there are not fused?

Neck bones that stay separate let the dolphin turn its head 90 degrees to chase fish around tight obstacles. Ocean dolphins have fused ones and cannot.

Male Amazon river dolphins have been seen rolling belly-up to launch what into the air for other males to chase?

A stream of urine is fired skyward while another male tracks it with his snout, behaviour that researchers think may pass on chemical signals.

Which ocean predator, famed for swimming far up rivers, is thought capable of preying on Amazon river dolphins?

Bull shark jaws are a rare danger because the species thrives in both salt and fresh water. Even so, no natural predator of the dolphin has ever been recorded.

Each rainy season, Amazon river dolphins leave the main river channels to hunt in which habitat?

Flooded forests become a vast seasonal sea where the dolphins weave between tree trunks after fish. Mothers and calves linger there longest, away from the main channels.

Which notorious Amazon fish, from the family Serrasalmidae, is a regular part of the Amazon river dolphin's diet?

Piranhas are only one item on a famously varied menu that takes in dozens of fish species, from croakers and cichlids to tetras.

Curious wild Amazon river dolphins have been reported grabbing hold of what belonging to passing fishermen?

Canoe paddles are a favourite plaything, and the dolphins also rub against boats and toss sticks and logs about. In captivity they proved bolder than bottlenose dolphins.

River dolphins, like every whale, are most closely related to which large land animals living in Africa today?

Hippopotamuses and whales descend from a shared semi-aquatic ancestor, which makes dolphins distant cousins of hoofed mammals such as cattle and deer.

What colour is a newborn Amazon river dolphin, years before it develops the famous adult blush?

Dark grey calves fade to a lighter shade in adolescence, and only adults go pink. Even then, some keep a darker back.

Which title does the Amazon river dolphin hold among the world's river dolphins?

Largest of all the river dolphins, a big male can weigh as much as two adult people. Unusually for river dolphins, the males grow bigger than the females.

Unlike whales of cold seas, the Amazon river dolphin has only a thin layer of what beneath its skin?

Blubber keeps ocean whales insulated, shields them and stores energy, needs that barely arise in a warm, shallow river, so river dolphins carry only a thin layer.

Which toxic metal, washed into Amazon rivers by gold mining, has been found in river dolphins' muscle and milk?

Mercury reaches the water mainly through illegal gold mining and builds up in fish-eaters, so scientists use the dolphins as sentinels of the river's health.

What human-built barriers threaten Amazon river dolphins by splitting their populations and blocking migrating fish?

Hydroelectric dams cut one population into small groups that can no longer interbreed, and they stop the fish migrations that feed the dolphins downstream.

Amazon river dolphins have been seen herding fish in coordinated hunts with which other Amazon predators?

Giant otters and the dolphins round up shoals together, and the partners barely compete because each prefers different kinds of fish.

What do male Amazon river dolphins carry in their mouths and wave about in displays linked to mating?

Floating branches or balls of hardened clay are carried mostly when many adults gather, and the show seems aimed at females while stirring up fights between rival males.

Which fatty organ in the Amazon river dolphin's bulging forehead can be reshaped by muscle to focus its sonar clicks?

The melon is a mass of fat that works as a sound lens, shaping clicks into a beam. A hunting boto fires 30 to 80 clicks a second into the murky water.

Which of the five classic senses do river dolphins appear to lack entirely, as their brains have no lobes for it?

Smell seems to be missing because river dolphins have no olfactory lobes. Taste may be weak too, since their taste buds are shrunken or absent.

Which smaller dolphin shares the Amazon's rivers with the Amazon river dolphin yet belongs to the ocean dolphin family?

Tucuxi look like small bottlenose dolphins, about 1.5 metres long, and although they live in fresh water they are not closely related to the boto.

Which South American country passed a law in 2012 declaring its pink river dolphins a national treasure?

Bolivia's president Evo Morales enacted the law to protect the dolphins, which live in the upper Madeira River basin and are counted as a subspecies of their own.

Beyond the Amazon basin, Amazon river dolphins also live throughout which great river system of Venezuela and Colombia?

Orinoco animals were proposed as a subspecies of their own in 1977, though genetic work suggests they descend from Amazon dolphins and barely differ.

Which naturalist reported on pink river dolphins while exploring Venezuela's rivers with botanist Aimé Bonpland in 1800?

Alexander von Humboldt set out to prove that South America's rivers interlock, and he was right: a natural channel joins the two great basins where the dolphins live.

Since about 2000, Amazon river dolphins have been illegally killed and used as bait to catch which kind of fish?

Catfish called piracatinga are scavengers drawn to rotting flesh, and growing demand for them turned dolphin carcasses into something fishermen could sell.

In 2018 the IUCN Red List moved the Amazon river dolphin into which threat category, citing a falling population?

Endangered status reflects deaths in fishing lines and at the hands of bait hunters, on top of pollution. Captive breeding is not seen as a way to save the species.

Local legends call the Amazon river dolphin the guardian of which other gentle water mammal of the same rivers?

Manatee hunters, the stories say, must first make peace with the dolphin, and harming the guardian itself is held to bring bad luck.

What name is given to the shapeshifting river dolphin of Amazon folklore, said to seduce villagers at night parties?

Encantado is Portuguese for 'charmed'. The beings are said to come from an underwater paradise without pain or death, yet they crave human company.

In which European country did an Amazon river dolphin named Baby live in one zoo for more than 45 years?

Germany's Duisburg Zoo kept Baby until he died in December 2020, aged at least 46. Most captive botos fared far worse, lasting under three years on average.

Chuckles, the last Amazon river dolphin kept in the United States, died in 2002 at which city's zoo?

Pittsburgh's last river dolphin, Chuckles, reached the age of 34, though most of the dolphins flown to American aquariums died within a few years.

The Amazon river dolphin belongs to which major group of cetaceans, alongside orcas, porpoises and narwhals?

Toothed whales hunt one prey animal at a time using sonar instead of filtering the sea, and the boto has around a hundred teeth in two different shapes.

Besides fish and crabs, which armoured reptiles can the Amazon river dolphin crack open with its molar-like back teeth?

Turtles are on the menu because the boto, unlike most dolphins, has two kinds of teeth: pointed ones in front to grip and ridged ones behind to crush.

Which of these South American countries has wild Amazon river dolphins living in its eastern lowland rivers?

Ecuador is one of only six countries that have the species, whose range covers about seven million square kilometres of river basin.

What does the Amazon river dolphin keep on its long snout as an adult, helping it feel for prey in river mud?

Stiff hairs on the beak act as feelers, and this sense of touch is believed to make up for eyesight that is little use in muddy water.

Instead of the tall triangular dorsal fin of ocean dolphins, what does the Amazon river dolphin have along its back?

A long low ridge runs from the middle of the body towards the tail, and it breaks the surface at the same moment as the tip of the snout when the boto comes up to breathe.

How does the Amazon river dolphin, like other dolphins studied, sleep while still surfacing to breathe?

Half its brain at a time rests while the other half stays alert, and the eye linked to the sleeping half closes while the other one stays open.

A genetic study found that inland Amazon charms sold as river dolphin parts mostly came from which animals instead?

Sheep and pigs supplied most of the charms sold far inland, and the rest came from a coastal dolphin, so none of those tested was a real boto.

Which natural channel in Venezuela links two great river basins, letting Amazon river dolphins cross between them?

Casiquiare water leaves one great river and flows south into a tributary of the other, making it the biggest natural link of its kind in the world.

Scientists proposed in 2014 that the river dolphins of which Brazilian river are a separate species?

Araguaia dolphins were split off on the strength of DNA and a wider skull, but the leading marine mammal society has not accepted them as a species.

Fossils of Isthminia, an extinct sea-going relative of the Amazon river dolphin, were found in which country?

Panama gave the animal its name, and its mostly marine life supports the idea that the boto's ancestors swam in from the sea before settling in rivers.

In 2023, over 150 river dolphins died in Brazil's Lake Tefé after a drought pushed what to record levels?

Water temperature in the shrunken lake reached 40°C, a record, and early investigators suspected the heat also made algae release a toxin that attacks the nervous system.

Which term describes how distantly related river dolphins on two continents separately evolved long beaks and tiny eyes?

Convergent evolution once led taxonomists to lump every river dolphin into one group, yet the boto is closer kin to ocean dolphins than to the Ganges species.