A 10km² area of forest, known as RPPN Feliciano Miguel Abdala, surrounded by agricultural land is now silent after losing the majority of its brown howler monkeys in an unprecedented epidemic.
Karen Strier from the University of Winconsin-Madison visited the forest in January 2017 and has been studying primates there for decades.
“It was just silence, a sense of emptiness,” she said. “It was like the energy was sucked out of the universe.”
Yellow fever is a virus carried by mosquitoes, and is found in Africa and South America.
Researcher Sergio Lucena Mendes said, “I am very surprised at the speed with which the outbreak is advancing through the landscape and by how the virus can jump from one patch of forest to another, even if they are hundreds of meters apart.”
So far Strier’s main study species, the Critically Endangered northern muriqui, doesn’t seem to be as susceptible to yellow fever as the brown howler monkey.
Scientists are planning to census the monkeys remaining on the reserve and study how the survivors regroup now that their previous social groups have been shattered.