How did we miss an entirely new species of river dolphin?

The newly discovered Araguaian Boto of Brazil is a rare and special dolphin indeed!  Sadly it is also in trouble and urgent conservation action is required to secure its future.  All river dolphins are vulnerable and need much greater protection than they currently enjoy. But Araguaian Botos are amongst the most endangered because they are only found in one river, there are not many of them – perhaps a total of 1000 to 1500 dolphins – and their genetic diversity is low; all these things add up to making the newly discovered Araguaian Boto species as particularly susceptible and vulnerable to human threats. It would only take one dam to be built on the river, or a fad using boto bait to catch fish to spread rapidly amongst local human communities, to result in certain extinction for this entire species.

The discovery that these botos represent a distinct species is vital in terms of overall river dolphin conservation plan and biodiversity priorities.  It is also hugely important information for WDC and our Brazilian partners and our efforts to protect botos in Brazil.  River dolphins are amongst the rarest and most endangered of all mammals; they survive only in South America and Asia and are under increasing threat from human populations. The Chinese River dolphin was declared extinct in 2006 unforgivably as a direct result of human threats; additional river dolphin species will also be lost from the world forever unless we take action now to halt the declines in their population numbers and accelerating degradation of riverine habitats suitable for them to thrive.  

So, how did a large charismatic species remain undiscovered for so long? After all these are big and often pink dolphins, seen regularly by the people sharing their fresh water homes in the flooded forest.  The reason is that on the outside they look like Amazon river dolphin found throughout the Amazon basin. It was only on very detailed study of their genetic make up that this incredible discovery was made. 

Detailed study of the Araguaian Botos of the Araguaian River in south eastern Brazil, including genetic analysis revealed significant differences between them and botos living in both the Amazon Basin (Brazil, Peru, Colombia and Ecuador) Inia geofrensis and the Madeira Basin of Bolivia Inia boliviensis.  They have given these botos the scientific name Inia araguaiansis.  They are evolutionary distinct and thus biologically distinct from both the Amazon river dolphin Inia geofrensis and the Bolivian river dolphin Inia boliviensis;  or in other words, all three are river dolphin species in their own right.  This is possible because the Araguaian Basin became separated from the Amazon River basin some 2 million years ago in geological time through tectonic movements, and are today further isolated from each other by geological barriers – enormous waterfalls and rapids, and the building of the Tucurui Dam. 

This discovery of an entirely new species of river dolphin highlights how little we still know about these incredible dolphins living in the rainforests of South America. We need to redouble our efforts to find out more and urgently take action to protect them from further harm and further loses. WDC is working with partners in Brazil, Peru, Colombia and Bolivia to protect these rare and remarkable dolphins.

Photo of Inia Araguaiaensis © Cristiane Moraes