Where were the gorillas hiding all this time?

In 2008 scientists discovered there were more gorillas than originally believed:

Scientists, who thought they were fighting a losing battle to protect the gorillas of central Africa, report a rare piece of good news. They have taken a new census of western lowland gorillas in the Republic of Congo, and say they found more than 125,000 -- nearly double what they thought were still living in the Congo and seven surrounding countries.