Greg Laden's Blog

The female gorilla in the photograph, nicknamed "Leah" by researchers, has twice made history. In 2005 Breuer and others observed her using tools--another never-before-seen behavior for her kind in the wild. Leah tested the depth of a pool of water with a stick before wading into it in Mbeli Bai, where researchers have been monitoring the gorilla population since 1995.

"Understanding the behavior of our cousins, the great apes, sheds light on the evolution of behavioral traits in our own species and our ancestors," said Breuer. "It is also interesting that this same adult female has been noted for innovative behaviors before."

Researchers say that few primates mate in a face-to-face position, known technically as ventro-ventral copulation. Instead, most primate species copulate in what's known as the dorso-ventral position, with both animals facing in the same direction. Besides humans, only bonobos had been known to mate face-to-face. On a few occasions, mountain gorillas have been observed in this position, but never photographed. Western gorillas have only ever been observed mating face-to-face in captivity.

"Our current knowledge of wild western gorillas is very limited, and this report provides information on various aspects of their sexual behavior," added Breuer. "We can't say how common this manner of mating is, but it has never been observed with western gorillas in the forest. It is fascinating to see similarities between gorilla and human sexual behavior."

The western lowland gorilla is listed as Critically Endangered as a result of illegal hunting, habitat destruction, and health threats such as the Ebola virus. Scientists estimate that the wild population has declined 60 percent in recent years. The Wildlife Conservation Society--the only organization working to protect all four gorilla subspecies--has been studying gorillas and other wildlife in the Republic of Congo since the 1980s. In 1993, WCS worked with the Congolese government to establish Nouabalé-Ndoki National Park.

Breuer's study received funding from the Brevard Zoo, Columbus Zoo and Aquarium, Cincinnati Zoo and Botanical Garden, Max Planck Society, Sea World & Busch Gardens Conservation Fund, Toronto Zoo, Wildlife Conservation Society, and Woodland Park Zoo.

Source: Wildlife Conservation Society