The boto encantado

In Amazonian folklore the boto is a river dolphin that turns into a young man, goes to dances and seduces young women. The story has long been used to explain pregnancies when the father is not named.

Portuguese Wikipedia tells the story as it is known in the riverside communities along the Amazon's main tributaries. Early in the night the boto becomes a handsome young man, tall and strong, a keen dancer and drinker. He goes to dances and gatherings, courts the young women and never misses a meeting with them. Before dawn he leaps back into the river and becomes a dolphin again. English Wikipedia adds that a female boto takes the form of a lovely, well-dressed young woman, that the shape-changer is known as an encantado, and that local tales say killing a dolphin brings bad luck. The New York Times (2007) notes that he wears a white hat to hide his blowhole.

Luís da Câmara Cascudo's Dicionário do Folclore Brasileiro also describes a protective boto. It steadies canoes in rough water and storms, drives fish towards the shore within reach of fishermen, and keeps company with boats carrying pregnant women. Cascudo observed that the boto is blamed for acts it never committed and always takes the blame for adultery and lost virginity.

The New York Times counts the boto among the Amazon creatures used to account for unwelcome or embarrassing events. In 2018 Agência Brasil interviewed a judge who said that reading these cases shows what lies behind the legend: sexual violence against girls, usually by members of their own family. She said the story is still repeated because girls who become pregnant cannot say who the father is, out of fear when he is a close relative, or out of shame. Wikipedia reports that some believe the myth has served, and still serves, to hide incest in small, isolated river communities. It also mentions a suggestion that the story arose partly because dolphin genitals resemble human ones.