Dead dolphins washed up on the shore or drifting on the waters reveal the devastating impact of extreme weather events on wildlife.
Authorities say they are experiencing the most severe drought in 13 years and are worried that the death toll of river dolphins will rise.
The Brazilian government has launched an emergency operation to investigate dolphin deaths and rescue endangered animals. Brazil's Environment Ministry said there were signs that historic drought and high temperatures were leading to the death of fish and mammals living in rivers.