Disease wipes out gorillas.
Scientists estimate that, between 2001 and 2005, the virus killed 5,500 gorillas in just one 2,700 square kilometre region in west Africa.
The researchers tracked gorilla groups in and around the Lossi sanctuary in the Republic of Congo.
They found evidence of "massive gorilla die-offs" caused by the Zaire strain of the Ebola virus (Zebov).
A 2,700 square kilometre zone was "largely emptied" of gorillas.
The number killed was a conservative estimate, assuming only half the gorilla population density typical of the region.
The evidence suggested that Ebola was spreading from one gorilla social group to another.