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Elephants and gorillas in the Republic of the Congo's rainforests spend a lot of time hiding in the shadows - or so we thought. Using drone (无人机) surveys and AI processing, scientists have discovered an extensive network of mysterious open clearings among the trees. Animals like elephants, gorillas visit these muddy areas, called bais, in the languages of the Indigenous Ba'Aka, to search for vital nutrition and maintain their complex social networks. The numerous playgrounds are visible in satellite images, and AI analysis is helping researchers find them more effectively.

The discovery began in 2021 when Sylvain Ngouma and Evan Hockridge came upon a massive clearing during fieldwork in Odzala-Kokoua National Park and found a trail (踪迹) of wet, pot-sized footprints leading through the woods to the open roundabout. Hockridge, who had thought bais were abnormal, says, "I had it backward. It kind of hit me when I was there. You can't understand animal interactions without first understanding bais."

For the next three summers, the team investigated the clearings. They analyzed camera-trap images, confirming what local people had told them - that these natural clearings are crucial gathering grounds for some of the world's most endangered mammals. The bais, they realized, are big melting pots, big playgrounds, for a collection of forest animals.

During the initial surveys, the team followed elephant trails to move through the rainforest from bai to bai. This process led Hockridge to wonder about a network. Although previous studies documented animal behavior in selected bais, no one had counted them or had the means to map their distribution. The team partnered with African Parks, using drones to scan known sites. They trained an AI algorithm (算法) to identify bais in satellite imagery, revealing 2,176 clearings in one park - 10 times more than previously recorded.

Bais are always near rivers or streams. Most are smaller than a city block, but few, at more than 100 acres, are bigger than some college campuses. "Bais are ultimately islands of resources, and animals produce these networks of trails to essentially navigate to and from a network of bais," Hockridge says. The researchers' map of bais, the first of its kind, is also a map of conservation priorities. "We find that a huge portion of the animal community depends on this unique ecosystem. These species don't have alternative habitats other than bais," Hockridge says.

The study is also a step toward solving the ultimate mystery: How did bais form? Many ecologists have argued that a combination of hydrology (水文学) and animal landscaping is at play. But definitive proof remains elusive. Now, with a map in hand and camera traps still in place, the research team is tracking long-term changes, which have implications for the maintenance of these crucial animal habitats.

"We have hypotheses (假说)," Andrew Davies, an ecologist in Harvard, says, "but the short answer is: we don't know."