Are Pink Dolphins Really Pink? The Truth About the Amazon River’s Strangest Mammal

Photo: Unsplash (free-use license).

The Amazon river dolphin — the boto, the pink dolphin, the bufeo — is the strangest cetacean most people have heard of and the most under-covered cetacean most people will never see. Below: what’s actually pink about them, why they’re pink at all, where the species sits on the threat scale, and the cluster of myths the species has accumulated.

Are pink dolphins really pink?

Yes — but not all of them, and not all the time.

The Amazon river dolphin (Inia geoffrensis) varies in colour from grey through silver-pink to a startling, unmistakable bubblegum pink. The pink intensifies with three things: age, sex (males tend to get pinker), and physical activity. After a fast swim, after a fight, after mating, an adult male boto can flush a deep pink across his flanks and back — the same way a person flushes when they exert themselves, and for the same reason. The colour is in the capillaries near the surface of the skin. Excitement, exercise and warmth bring blood close to the surface; the pink intensifies. Calm, cold, or relaxed animals are paler.

The other piece of the story: most botos have scarring. Adult males in particular accumulate a network of pale scars from in-fighting and from rough riverbed encounters, and the scarred regions can show pink because the pigment beneath has been disrupted. So a strongly-pink adult male is, in part, a record of his social and physical history.

The basic facts

• Length: Up to 2.5 metres for adult males; females noticeably smaller.
• Weight: Up to about 185 kg.
• Range: The Amazon and Orinoco river basins — Brazil, Peru, Colombia, Venezuela, Bolivia, Ecuador. There is also a separate, smaller, related species — the Bolivian river dolphin (Inia boliviensis) — which some authorities split out and others lump.
• IUCN status: Endangered (assessed 2018, last reviewed 2023).
• Diet: Catfish, piranha, freshwater turtles, crustaceans. The boto’s neck vertebrae are unfused, which lets it twist and turn after prey in a way ocean dolphins can’t.

What makes them weird

A short list of the things that make the boto unlike any cetacean you’d meet in saltwater:

The neck

The vertebrae in a boto’s neck are not fused. It can turn its head 90 degrees side-to-side. Marine dolphins can’t do this. The boto evolved this for a riverine life — for slithering between flooded tree roots, working through tangles of submerged forest, and snapping at fish in the kind of sediment-choked water where echolocation matters more than vision.

The forehead

The melon — the rounded forehead that all toothed cetaceans use to focus their echolocation — is unusually mobile in Inia. Botos can flex it like a putty ball, which gives them more directional control over their biosonar. Useful when you’re hunting through underwater vegetation.

The teeth

Botos have two kinds of teeth — pointed at the front (for grabbing prey) and molar-like at the back (for crushing). Almost no other cetacean has a differentiated dentition like this. It is probably an adaptation to a varied riverine diet that includes hard-shelled prey like turtles.

The eyes

Small. The Amazon is opaque with sediment for most of the year — vision is a low-priority sense. Echolocation runs the show.

Why they’re endangered

The IUCN’s 2018 reassessment moved the Amazon river dolphin from Data Deficient to Endangered. The drivers are unfortunately familiar:

• Bycatch in commercial fisheries. Particularly gillnets set for catfish.
• Direct killing for fish bait. Botos are sometimes killed deliberately and used as bait for piracatinga, a scavenger catfish exported to Colombia and elsewhere. This practice was banned in Brazil in 2014, but enforcement is patchy.
• Habitat fragmentation. Hydroelectric dams in the Madeira, Tocantins, and other tributaries cut populations off from each other. River dolphin populations are not as mobile as ocean dolphins; once cut off, they stay cut off.
• Mercury contamination from artisanal gold mining. Top-of-food-chain animals concentrate methylmercury. Some Amazon populations now show mercury loads at the top of the documented range for cetaceans.
• Climate-driven hydrological extremes. The 2023–2024 Amazon drought reached temperatures in some lakes and oxbows above 39°C. Hundreds of botos and tucuxi died in those events. Scientists at Mamirauá documented the largest single-species die-off ever recorded for the species.

The mythology — and why it might be worth keeping

Almost every Amazonian culture has a version of the same story: the boto is a shape-shifter who, on full-moon nights, becomes a tall, charming young man in a white suit and a wide hat, walks into riverside villages, and seduces young women. Children with no obvious father are sometimes said to be a boto’s. The hat hides the dolphin’s blowhole, which would otherwise give him away.

It’s an extraordinary, recurring myth, and conservationists have started to take it seriously — not as biology but as cultural protection. Communities that hold the boto sacred are demonstrably less likely to kill them deliberately. There’s a real argument that respecting and amplifying indigenous boto mythology is one of the more effective protection strategies actually available, and we tend to agree.

Where you can see one

Several lodges in the central Amazon — particularly in the Mamirauá Sustainable Development Reserve — run respectful, regulated boto encounters. The well-run ones don’t feed the dolphins, don’t allow contact, and keep the swimming activities at arm’s length. The badly-run ones do all three, and we don’t recommend them. If you’re going, check whether the operator is supervised by the Mamirauá Institute or an equivalent science partner.

Reading further

For more on the Amazon’s mammals, see our Amazon wildlife archive. For the broader picture on freshwater dolphins and porpoises, our dolphin and porpoise overview covers the family, and our earlier piece on why pink dolphins are endangered goes deeper into the policy side.

External background: the IUCN Red List entry for Inia geoffrensis is the canonical status reference, and the Smithsonian’s coverage of the species is a good general explainer.

If you’ve seen one in the wild and want to send us a photo, please do — contact us here.

— Theo Hartwell, birds & primates (and, today, dolphins)