While many associate dolphins with the ocean, a unique group thrives deep within the freshwater systems of South America. The Amazon and Orinoco river basins are home to cetaceans adapted to a complex, forested aquatic world. These river-dwelling creatures live their entire lives in the winding, often murky, freshwater channels that pulse through the heart of the continent.
Species and Unique Appearance
The most recognized freshwater dolphin is the Amazon river dolphin (Inia geoffrensis), often called the “boto.” Its most notable feature is the pink hue that some adults develop. The dolphins are born grey and gradually turn pinker with age. The color’s intensity can be influenced by blood capillaries near the skin, diet, and sunlight exposure. Males tend to be more vividly pink, a trait possibly enhanced by scar tissue from aggressive interactions.
These dolphins also possess distinct physical adaptations. They have a long, slender snout for probing the riverbed for food and unfused vertebrae in their necks. This flexibility allows them to turn their heads 90 degrees, helping them maneuver around obstacles in the flooded forest. Their eyes are small, but their eyesight is more developed than that of other river dolphins. A less famous species, the tucuxi (Sotalia fluviatilis), also inhabits the Amazon basin but more closely resembles its oceanic relatives and is not known for a pink color.
Habitat and Diet
Amazon river dolphins inhabit freshwater ecosystems across several South American countries, including Bolivia, Brazil, Colombia, and Peru. Their environment transforms with the seasons. During the rainy season, when rivers overflow, these dolphins move into the flooded forests. Their agile bodies are suited for navigating this complex underwater world of submerged trees.
Their diet is diverse, consisting of more than 50 species. Using their specialized teeth—sharp conical ones in the front and flatter ones in the back—they consume a wide array of prey. This includes many types of fish like catfish and piranhas, crustaceans like river crabs, and small turtles. They rely heavily on echolocation to find meals in the dark, sediment-rich waters of the Amazon.
Behavior and Cultural Significance
These river dolphins are more solitary than their marine cousins, often observed alone or in small mother-and-calf pairs, though they sometimes gather to feed. They are inquisitive and playful, seen approaching canoes, interacting with sticks, and playing with other river animals like turtles. They can also swim backwards and upside down, which may help them scan the river bottom more effectively.
The Amazon river dolphin holds a prominent place in local folklore, where it is known as the “encantado,” or enchanted one. According to legend, these creatures are shapeshifters capable of transforming into handsome men who emerge from the river at night. The encantado attends festivals and seduces young women before returning to his underwater realm by morning. This mythology has woven the dolphin into the cultural fabric of Amazonian communities.
Threats and Conservation Status
The Amazon river dolphin is under significant pressure from human activities. A severe threat is mercury pollution from illegal gold mining, which contaminates rivers and accumulates in the food chain. Dolphins ingest the toxic metal by consuming contaminated fish. Widespread deforestation and the construction of hydroelectric dams also degrade and fragment their habitat, isolating populations.
These dolphins also face direct threats from fisheries. They can become accidentally entangled in fishing nets, a problem known as bycatch. In some regions, they are intentionally killed by fishermen who view them as competition for fish or use their meat as bait for the “mota” catfish fishery. Due to these threats, the International Union for Conservation of Nature (IUCN) has classified the Amazon river dolphin (Inia geoffrensis) as Endangered, signifying a very high risk of extinction in the wild.