Strange, pink, small-eyed freshwater dolphins glide through today’s turbid waters of the Amazon river basin. But they are fast approaching extinction.
The Amazon river dolphin (Inia geoffrensis), or “boto”, is one of the few remaining dolphins on the planet that are restricted to freshwater, with two other superficially similar species in south Asia.
at the University of Dundee in the UK and his colleagues have spent more than two decades studying the botos around Mamirauá Sustainable Development Reserve in the Brazilian Amazon. Using their wealth of long-term data, Martin and at the National Institute of Amazonian Research in Brazil calculated population trends.
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The team used 22 years of survival and reproductive data on more than 650 dolphins to create a model that predicts the botos population in the coming decades.
“When we first started this work, there were dolphins everywhere, and we thought of them as actually very abundant,” says Martin.
But their model delivered a shock. “It knocked our socks off,” says Martin. “The decline is far more profound than we had imagined.”
In all six of their simulations, the number of dolphins is predicted to fall by at least 95 per cent in less than 50 years. The extinction of the boto may occur in just over a century.
In this part of the central Amazon, the botos’ precipitous decline is largely due to entanglement and drowning in monofilament gill nets, and people catching and using the dolphins as fish bait.
Martin says that the boto is treading the same path as the baiji (Lipotes vexillifer), a river dolphin native to the Yangtze river in China that is probably now extinct. “All of the true river dolphins – the ones that can’t get away from humans – they’re all going down the plughole.”
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Botos were the most numerous among river dolphins and were assumed to be in a fairer condition, he says. “But the reality is, it’s devastating how fast they’re disappearing.”
One change that could have a big impact on the dolphins’ chances would be increased enforcement of existing laws on gill net use, says Martin.
at the Federal University of Juiz de Fora in Brazil says the extinction prediction is “really alarming”. But Frias argues that the central Amazonian dolphins may be experiencing challenges that don’t necessarily impact the entire range of the species.
“It is crucial to identify if there is population decline in other regions,” she says.
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