Conservation workers have seen the first evidence for tool use in wild gorillas. One instance, caught on film in the Republic of Congo’s Nouabalé-Ndoki National Park, involved a lowland gorilla using a metre-long stick to test the depth of water ahead of her as she cautiously waded into a swampy pool.
In contrast, most examples of tool use in great apes are related to food extraction and preparation. Researchers argue that this new type of tool use may be more widespread, and could hint at abstract reasoning.
Captive gorillas have been observed throwing objects and using sticks to extract food, but gorillas were the only great ape never seen using similar objects in the wild. Chimps frequently use twigs as dipping sticks to gather termites and rocks as hammers to crush nuts.
Researchers have speculated that gorillas were not seen using tools because they eat different food. But mountain gorillas have been seen using food-processing techniques of comparable complexity – such as intricately folding nettles and thistles to protect themselves from stinging spines.
Depth probe
Thomas Breuer of the New York city-based Wildlife Conservation Society and his team observed the gorilla tool use in Nouabalé-Ndoki National Park in October and November 2004. The have been using specially constructed viewing platforms to watch western lowland gorillas in Mbeli Bai, a swampy rainforest clearing, since 1995.
They saw a female gorilla nicknamed Leah attempting to wade through a pool of water created by elephants. After quickly sinking waist deep, she got out of the water and picked up a metre-long stick, says Breuer. She then re-entered the water and repeatedly prodded the stick ahead of her as if to test for depth. She advanced about 10 metres before returning to her wailing infant on the edge of the pool.
“It was exactly how you or I might have tested the depth of the water,” Breuer told New Scientist, by satellite phone from a forest clearing in Nouabalé-Ndoki.
A second example was also captured on film, when Efi, a gorilla from another group, used a stick to lean on for support while she foraged for food with her free hand. She then used the same stick as a bridge to help her cross a patch of swampy ground, says Breuer.
"Incredibly intuitive"
“Both cases seem related to the problems of locomotion in this swampy forest clearing,” says Breuer. This suggests that the tool use stems from an ecological need.
“Most great ape tool use is based around the retrieval of food,” notes Gillian Sebestyen-Forrester who studies gorilla communication at the University of Sussex, UK. But the “incredibly intuitive” behaviour of using a stick to test water depth is something quite different, she says.
“The gorillas have understood in some capacity that they can extend their sensory experience and find out more about their environment by physically extending their bodies with an inanimate object,” she says. "This suggests that the gorilla is capable of some mental calculation and abstract thought."
Footprints of gorillas were found on branches in nearby clearings suggesting their use as bridges could be widespread, says Breuer.
Journal reference: PLoS Biology (vol 3, issue 11, e380)
In contrast, most examples of tool use in great apes are related to food extraction and preparation. Researchers argue that this new type of tool use may be more widespread, and could hint at abstract reasoning.
Captive gorillas have been observed throwing objects and using sticks to extract food, but gorillas were the only great ape never seen using similar objects in the wild. Chimps frequently use twigs as dipping sticks to gather termites and rocks as hammers to crush nuts.
Researchers have speculated that gorillas were not seen using tools because they eat different food. But mountain gorillas have been seen using food-processing techniques of comparable complexity – such as intricately folding nettles and thistles to protect themselves from stinging spines.
Depth probe
Thomas Breuer of the New York city-based Wildlife Conservation Society and his team observed the gorilla tool use in Nouabalé-Ndoki National Park in October and November 2004. The have been using specially constructed viewing platforms to watch western lowland gorillas in Mbeli Bai, a swampy rainforest clearing, since 1995.
They saw a female gorilla nicknamed Leah attempting to wade through a pool of water created by elephants. After quickly sinking waist deep, she got out of the water and picked up a metre-long stick, says Breuer. She then re-entered the water and repeatedly prodded the stick ahead of her as if to test for depth. She advanced about 10 metres before returning to her wailing infant on the edge of the pool.
“It was exactly how you or I might have tested the depth of the water,” Breuer told New Scientist, by satellite phone from a forest clearing in Nouabalé-Ndoki.
A second example was also captured on film, when Efi, a gorilla from another group, used a stick to lean on for support while she foraged for food with her free hand. She then used the same stick as a bridge to help her cross a patch of swampy ground, says Breuer.
"Incredibly intuitive"
“Both cases seem related to the problems of locomotion in this swampy forest clearing,” says Breuer. This suggests that the tool use stems from an ecological need.
“Most great ape tool use is based around the retrieval of food,” notes Gillian Sebestyen-Forrester who studies gorilla communication at the University of Sussex, UK. But the “incredibly intuitive” behaviour of using a stick to test water depth is something quite different, she says.
“The gorillas have understood in some capacity that they can extend their sensory experience and find out more about their environment by physically extending their bodies with an inanimate object,” she says. "This suggests that the gorilla is capable of some mental calculation and abstract thought."
Footprints of gorillas were found on branches in nearby clearings suggesting their use as bridges could be widespread, says Breuer.
Journal reference: PLoS Biology (vol 3, issue 11, e380)
http://news.nationalgeographic.com/news/2005/09/0930_050930_gorilla_tool.html
Evidence that all great ape species use tools also adds insight to human evolution, Breuer added. It suggests that tool use—once thought a distinguishing characteristic of humans—emerged in primates before humans split from the great apes.
