So far, only two species of primates (besides humans) were known to mate face-to-face in the wild: bonobos and orangutans. But the Wildlife Conservation Society has presented a pair of wild western lowland gorillas in Africa having face-to-face sex. This had been seen in Zoo mountain gorillas, but never seen in the lowland gorillas and have never been photographed in the wild. The photos were made in 2005, by conservation biologist Thomas Breuer. Breuer is leader of a long-term research of gorilla social organization and sexual selection at Mbeli Bai in Nouabalé-Ndoki National Park, in Congo.
Surprisingly, the same female, Leah, was seen using tools in the wild in 2005, a first for the gorillas: the female was observed using a walking stick to cross a swampy forest clearing.
"Seeing the similarity between humans and gorillas in this respect is fascinating," Breuer, of Germany's Max Planck Institute and the New York-based Wildlife Conservation Society, told National Geographic News.
While the majority of monkeys mate in the "dog style", "Bonobos [mate face-to-face] routinely-zoo gorillas and zoo chimps too," said Craig Stanford, an expert in great ape behaviors at the Jane Goodall Research Center, from the University of Southern California (USC).
It may look like a couple having a special bond, but male gorillas have a harem, and Leah is just one of four females of her male's harem.
Leah has a low status inside the harem, despite her developed tool-using skill. For the moment, it cannot be observed if face-to-face mating is more spread amongst gorillas.
"What we know about these gorillas is just a tiny bit. So I'm kind of hesitant to say Leah is particularly special. I think we're [beginning] to understand the flexibility of their society and natural behavior. In time we may see more," said Brauer.
"It is an interesting observation and raises questions about why they sometimes engage in it. There may be practical considerations given the apes' marshy habitat, for example. Perhaps a female doesn't want to be face down in the swamp," Diane Doran-Sheehy, anthropology chair at Stony Brook University, in New York, and a grantee of the National Geograpkhic Society's Committee for Research and Exploration, told National Geographic News. During her researches, she has seen over 500 gorillas mating in the wild, but never face-to-face.
Western lowland gorillas are critically endangered; their populations have plummeted up to 60% in the recent years due to illegal hunting, habitat loss, and Ebola fever.
"It leads me to think about how similar gorillas can be to humans, [and yet] we humans are destroying them. I'm thinking about their conservation, because we're not going to see these things in the future if we continue to threaten [these animals]," said Brauer.