Amazon River Dolphin (Boto): Why Do Some Turn Pink?

Scientific name: Inia geoffrensis
Also called: Amazon river dolphin, boto, pink river dolphin
Size: Up to ~2.4 m (8 ft) and ~200+ kg (450 lb)
Range: Amazon–Orinoco basins (Brazil, Peru, Colombia, Ecuador, Venezuela, Bolivia, Guyana)
Ecological role: Large freshwater apex predator
Conservation: Internationally protected; facing dams, pollution, bycatch, vessel strikes, and habitat degradation

1) The Pink Mystery: What Really Causes the Color?

• Born gray: Calves are gray; many adults—especially males—develop pink to rose coloring with age.

• Likely drivers (multi-factor):

• Vascular/skin factors: Rich capillary beds and thinner skin make blood flow more visible during activity or social interactions.

• Scarring hypothesis: Repeated rubbing or minor scuffles can leave pink scar tissue that brightens with age.

• Camouflage hypothesis: During flood season, some waters turn reddish/brown; a pinkish hue may reduce visibility in turbid water (still a hypothesis).

• Sexual selection: In some areas, rosier males may be more attractive in courtship displays.

2) Built for Flooded Forests: Anatomy at a Glance

• No tall dorsal fin: Instead, a low hump to slip between submerged branches.

• Flexible neck: Unfused cervical vertebrae allow the head to turn side-to-side—perfect for weaving through flooded forest (varzea/igapó).

• Teeth for variety: Conical gripping teeth at the front and more molar-like teeth behind for crushing crabs and river turtles.

• Big, rounded pectoral fins: Precise maneuvering and quick braking in tight, obstacle-rich water.

• Echolocation: Sophisticated sonar for low-visibility hunting.

3) Habitat & Seasonal Movement: Following the Water Level

• Hydrologic rhythm: The basin pulses between low-water and flood seasons each year.

• Flood season: Botos move into seasonally flooded forests to feed and raise young amid submerged roots and fruiting trees.

• Low water: They shift back to main channels, oxbow lakes, and large tributaries.

• Diet: Primarily fish, plus crabs and freshwater turtles; flexible foraging in complex, woody habitats.

4) Why They’re Getting Harder to See

Key threats

1. Dams & flow alteration: Block fish migrations, change current speeds, and disrupt floodplain timing critical to foraging and breeding.

2. Pollution (including artisanal gold mercury): Toxins bioaccumulate up the food web, affecting health and reproduction.

3. Bycatch & illegal take: Gillnets and longlines cause entanglement; in a few areas dolphins are still harmed or exploited.

4. Boats & noise: Collisions and underwater noise can interfere with echolocation and communication.

5. Habitat loss: Deforestation, shoreline hardening, and wetland infill shrink flooded-forest nurseries.

What helps

• Basin-scale management of rivers–lakes–wetlands; safeguarding floodplain forests and travel corridors.

• Better dam design/operations (environmental flows, fish passage) and robust impact screening.

• Net-gear transition (no-gillnet zones, alternative gears) plus compensation and training for fishers.

• Pollution control (especially mercury) and consistent water-quality monitoring.

• Vessel measures: Speed limits and routing in hotspot channels; quieter engines where possible.

• Science & monitoring: Acoustic surveys, photo-ID, standardized boat transects to track trends over time.

5) Meet the Neighbors: Three Other South American “River Dolphins”

1. Bolivian river dolphin (Inia boliviensis) — Upper Bolivian Amazon; relatively isolated from botos by rapids; lower competition where it occurs.

2. Araguaia river dolphin (Inia araguaiaensis, “Araguaian boto”) — Araguaia–Tocantins system (Brazil); smaller, gray-pink, separated from I. geoffrensis by genetic evidence.

3. La Plata river dolphin / Franciscana (Pontoporia blainvillei) — The smallest of the group; inhabits coastal/estuarine waters along Brazil–Uruguay–Argentina; entirely gray, not pink.

6) Why Botos Are So Hard to Spot

• Optical camouflage: Turbid, tea-stained water + mottled light reduce detectability (especially in flood season).

• Structural complexity: Submerged forests and woody debris create a maze that masks movement.

• Cautious behavior at low densities: In disturbed waters, individuals may avoid boats early.

7) Responsible Watching: Visitor Guidelines

• Book licensed operators who follow distance/speed rules and never feed dolphins.

• Choose low-noise, slow approaches; avoid tight channels with high speed.

• Keep hands off; use long lenses and follow local drone rules.

• Prioritize dawn/late-day outings with good visibility and minimal traffic.

FAQs

Why are males pinker than females?
Likely a mix of age, blood flow/skin traits, and scarring; sexual selection could favor pinker males in displays.

What do they eat? Will they bite people?
Mostly fish, plus crabs and small turtles. They do not seek conflict with people; disturbance or harassment is what creates risk.

When/where are sightings best?

• Flood season: edges of flooded forests, confluences, and quiet creeks.

• Low water: main channels, oxbows, and large lakes with slower flow.

How do they turn their heads?
Botos have unfused neck vertebrae, allowing lateral head movement uncommon in marine dolphins.

animal tags: boto

We created this article in conjunction with AI technology, then made sure it was fact-checked and edited by a Animals Top editor.