we found an astonishing amount of gorillas , '' said Rainey , speaking from the International Primatological Society Congress in Edinburgh , Scotland . Though researchers did spot some gorillas , they based their estimate on the number of gorilla nests found at the site , Rainey said . Each gorilla makes a nest to sleep in at night . `` This is the highest-known density of gorillas that 's ever been found , '' Rainey said . Watch a glimpse of gorilla life in African swamp '' Western lowland gorillas are listed as critically endangered , the highest threat category for a species . Their populations are declining rapidly because of hunting and diseases like Ebola hemorrhagic fever , whose symptoms include diarrhea , vomiting and internal and external bleeding . Take a closer look at the Western lowland gorilla '' While the discovery in northern Congo indicates that the gorilla population remains stable in some areas , it is likely that gorillas will remain critically endangered because the threats facing the species are so great , Rainey said . iReport.com : Share photos and video of gorillas in zoos or the wild `` We know very little about
-LRB- CNN -RRB- -- An estimated 125,000 Western lowland gorillas are living in a swamp in equatorial Africa , researchers reported Tuesday , double the number of the endangered primates thought to survive worldwide . Forest clearings draw large numbers of Western lowland gorillas searching for food . `` It 's pretty astonishing , '' Hugo Rainey , one of the researchers who conducted the survey for the U.S.-based Wildlife Conservation Society , told CNN Tuesday . The last census on the species , carried out during the 1980s , estimated that there were only 100,000 of the gorillas left worldwide . Since then , the researchers estimated , the numbers had been cut in half . WCS survey teams conducted the research in 2006 and 2007 , traveling to the remote Lac Tele Community Reserve in northern Republic of Congo , a vast area of swamp forest . Acting on a tip from hunters who indicated the presence of gorillas , Rainey said that the researchers trekked on foot through mud for three days to the outskirts of Lac Tele , about 80 kilometers -LRB- 50 miles -RRB- from the nearest road . `` When we went there ,