Gorilla Census

Almost all the world’s gorillas live near the equator in Central Africa (see map). To protect the endangered animals, scientists need to know which regions they inhabit and how many of them there are. To find out, teams of researchers like Maisels spent months at a time trekking through national parks and other wilderness areas. They camped in the forest, arose before dawn, and hurried to eat breakfast before any hungry insects woke up. Then they walked a straight line through the forest to gather evidence of animals around them. They repeated this thousands of times over more than a decade to survey large swaths of the wilderness.

Almost all the world’s gorillas live near the equator in Central Africa (see map). The animals are endangered. To protect them, scientists need to know which regions they inhabit and how many of them there are. To find out, teams of researchers like Maisels spent months at a time on expeditions. They trekked through national parks and other wilderness areas. They camped in the forest and got up before dawn. They had to eat breakfast quickly, before any hungry insects woke up. Then they walked a straight line through the forest to gather evidence of animals around them. They repeated this thousands of times over more than a decade. Over time, they surveyed large portions of the wilderness.

Finding gorillas isn’t easy. If the big apes hear people coming, they usually run away. Instead, the scientists looked for the nests that gorillas build to sleep in. Apes make these beds of sticks and leaves each evening and abandon them the next day. When the team spotted an ape nest, they checked under it for droppings. The shape of the dung told them whether the nest was used by a gorilla or a chimp.

After dozens of expeditions, the researchers had enough data to estimate the total number of gorillas in western Africa. They calculated that there were more than 360,000 of the apes in 2013—at least 100,000 more than previously known.

Unfortunately, over the course of the study, the population shrank by an average of 2.7 percent each year. Poaching, disease, and habitat loss are making it harder for gorillas to survive. 

A healthy gorilla population can help the whole forest, says Maisels. As the apes eat fruits, they spread seeds in their dung, allowing new trees to grow. Maisels hopes that the data scientists have gathered will bring new protections for the animals. “We should go to great lengths to reverse the damage we’ve done,” she says.

Finding gorillas isn’t easy. If the big apes hear people coming, they usually run away. Instead, the scientists looked for the nests that gorillas build to sleep in. Apes make these beds of sticks and leaves each evening. They abandon the nests the next day. When the team spotted an ape nest, they checked under it for droppings. They studied the shape of the dung. That told them whether the nest was used by a gorilla or a chimp.

After dozens of expeditions, the researchers had the data they needed. It was enough to estimate the total number of gorillas in western Africa. They calculated that there were more than 360,000 of the apes in 2013. That’s at least 100,000 more than previously known.

Unfortunately, the population dropped over the course of the study. It shrank by an average of 2.7 percent each year. Poaching, disease, and habitat loss are making it harder for gorillas to survive.

A healthy gorilla population helps the whole forest, says Maisels. As the apes eat fruits, they spread seeds in their dung. That allows new trees to grow. Maisels hopes that the data scientists have gathered will help gorillas. It could inspire new protections for the animals. “We should go to great lengths to reverse the damage we’ve done,” Maisels says.