TrilobitesWhy Chimps and Gorillas Form Rainforest FriendshipsIn a Congolese national park, great apes of different species interact socially, with individuals clearly recognizing one another.“Most of what we’d been told about the interactions between these two species is that they’d be competitive or they would avoid each other,” said Crickette Sanz, an anthropologist at Washington University in St. Louis who witnessed such a scene for the first time in 2000.But over two decades of observations at Nouabalé-Ndoki National Park in the Republic of Congo, she and her colleagues recorded yearslong relationships and other forms of social interactions between individual chimpanzees and gorillas.While the populations of chimpanzees in East and West Africa have been well studied over the past several decades, the bands present in Congo are less well known, Dr. Sanz said.Unfortunately, such co-feeding can provide opportunities for the transmission of diseases like Ebola, waves of which have killed thousands of chimpanzees and gorillas over the past two decades."