Gorillas have been spotted for the first time using tools in the wild. The observation adds the species to a growing list of animals, including chimpanzees, orangutans, dolphins, and crows, that can use sticks, rocks, and even sponges to help them perform specific tasks.
Scientists had known that gorillas could use tools in captivity, for example to retrieve food or toys that are out of reach, but despite decades of observations, no one had documented them using tools in the wild. All of that changed during "a very lucky period" last fall at the Mbeli Bai observation site in northern Congo, say primatologists Thomas Breuer, Mireille Ndoundou-Hockemba, and Vicki Fishlock of the Wildlife Conservation Society.
In early October, the team watched as a female named Leah cautiously waded into a murky pool that had recently been dug by feeding elephants. When the water reached her waist, Leah returned to shore. She entered the water again but this time broke off a meter-long branch that she used as a walking stick to test the water depth in front of her. In late November, the team saw a female named Efi, who belongs to a different troop, using a large branch first as a balance as she foraged for aquatic plants and then as a bridge to help her cross a swampy patch of ground. The team describes its observations in the November issue of PLoS Biology. Researchers have been documenting gorilla behavior for nearly a decade at Mbeli Bai without ever noticing such tool use.
One reason tool use is so seldom seen among wild gorillas is that the animals don't appear to have much need for tools. Most gorilla studies have taken place in the forests of Uganda and Rwanda, an ecosystem that researchers have dubbed "a big salad bowl" with food that is plentiful and easy to reach without tools, says evolutionary psychologist Andrew Whiten of the University of St. Andrews in Fife, U.K. But gorillas can rise to the occasion when necessary. "I see gorillas as very smart and very prone to using tools if the problem presents itself," says gorilla expert Hugh Bailey of Woodland Park Zoological Gardens in Seattle, Washington.
The two sightings do not move gorillas into the ranks of tool-use experts such as chimpanzees, Whiten and Breuer agree. Chimps use tools routinely and often depend on ant or termite fishing to survive. When gorillas use tools, Breuer says, "it's an exceptional occasion."
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