Death of 185 endangered pink dolphins sparks extinction fears

Investigations are underway to determine the cause of the dolphin deaths while other wildlife in the area are also suffering.

Investigators have discovered seven more rare pink dolphins dead in Brazil as river levels continue to plummet, Yahoo News Australia can reveal.

Listed as endangered on the international Red List of threatened species, populations of Amazon River dolphins were already decreasing because fishermen hunt and butcher them to use as bait, and industrialists have been damming their habitat. This year, a record number of deaths linked to water quality have been catalogued as part of an investigation by Sea Shepherd Brazil, local organisations and experts.

Three images of dead pink dolphins lying on the banks of the Amazon.
A total of 30 dead dolphins have now been found at Coari. Source: Sea Shepherd Brasil

The most recent discovery was made over the weekend in the town of Coari. The find takes the region’s total dolphin death toll to 30, of which 23 were the rare pink species. But 195km west along the Amazon River in Tefé things are worse, a total of 155 dead dolphins have been counted over the last few weeks. Investigators fear there have been many more deaths in regions they are yet to visit.

Key Amazon dolphin facts

  • The pink dolphins (Inia geoffrensis) are known locally as red boto

  • The other species (Sotalia fluviatilis) more closely resembles a marine dolphin

  • Both species are listed as endangered.

Is drought the only reason so many dolphins are dying?

Sea Shepherd Brazil president Nathalie Gil told Yahoo several of the dolphins are undergoing necropsies to determine the exact cause of death. She believes there are several factors behind the catastrophe that go beyond simple drought.

While this year’s drought is the worst in over 120 years, the Amazon River does recede substantially every year during the dry season, and the tributaries that connect to Coari and Tefé begin to bottleneck and essentially become lakes.

In these newly created pools of water, a scientific team from Instituto Mamiraua recorded temperature highs of up to 41 degrees in these waters. “It’s fantastically high. Imagine if you were in this pool for the whole day,” Gil said.

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But while the high water temperature is likely stressing the dolphins, Gil believes diet could also be influencing their demise. That’s because herbivorous manatees are dying at much lower rates than fish-eating dolphins.

While still plentiful, fish have been dying in great numbers and it’s possible the dolphins who eat them are poisoned. The fish deaths are likely linked to toxic algal blooms, which are made worse by untreated water draining into the rivers from nearby villages.

“And now that the river is low, everything from their households is going to the river with a lot less dilution,” Gil said. “So the river is potentially highly contaminated right now.”

Race to protect dolphins from extinction

With climate change set to make droughts more extreme and frequent, Gil is extremely worried about what this will mean for the Amazon’s dolphins.

“It's a huge effect to lose this amount of dolphins considering they are very slow to reproduce. Before this stress happened we worried they probably could disappear in three decades, so with this threat on top it could be faster,” she said.

“It’s now crucial to understand how many dolphins are left so we can expose the urgency needed to take care of them.”

Sea Shepherd Brazil is raising funds to continue to monitor dolphins in the Amazon. Donations can be made here.

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