Pink River Dolphin

Once thought to be naturally protected by local taboos, the boto is now in steep decline across much of its range. A 22-year monitoring study in Brazil's Mamiraua Reserve — one of the better-protected parts of its range — recorded the population falling by roughly 5.5% every year, a rate fast enough to halve numbers within little more than a decade. On the strength of evidence like this, the IUCN reclassified the species as Endangered in 2018, having previously listed it as Data Deficient. Because the dolphins are spread thinly across vast, hard-to-survey river networks, there is no trustworthy global population figure — the honest answer is that no one knows exactly how many remain, only that the trend is downward.

Botos are superbly adapted to murky, obstacle-filled freshwater. They navigate and hunt by echolocation, emitting clicks to find prey in water where eyesight is almost useless. Their stocky bodies carry a low ridge rather than a tall dorsal fin, and uniquely flexible, unfused neck vertebrae let them twist and reach into flooded forest to take fish, river turtles, crabs and even small caimans — one of the widest diets of any toothed whale. During the annual flood season they swim among the trees, dispersing through the forest before returning to main river channels as waters fall. Calves are born singly after about an 11-month gestation, measuring around 80 cm, and stay with their mothers for a year or more.

The boto's decline is overwhelmingly human-driven. Many drown after becoming entangled in nylon gillnets, while others are deliberately harpooned to be used as bait for piracatinga, a scavenging catfish. Layered on top is mercury pollution: illegal gold mining releases the metal into rivers, where it accumulates up the food chain into these long-lived top predators. Dams fragment populations and block movement, and extreme events tied to a warming climate add new dangers — in 2023, scores of botos died in a single Amazon lake during a record drought and heatwave. Together these pressures make the freshwater habitat itself the front line for the species' survival.

Protecting botos is mostly about protecting rivers and the people who share them. Practical work includes removing or modifying deadly gillnets, supporting fishers to abandon the bait-hunting trade, monitoring mercury levels, responding to stranded or entangled animals, and safeguarding key stretches of flooded forest. Because the dolphins cross national borders, lasting gains depend on locally led teams who know the waterways and can build trust with riverside communities — the kind of frontline partners that conservation funders increasingly back rather than parachuting in from outside.