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Friday, September 3, 2010

Chimps seek out and de-arm snares in Bossou, Guinea

"Waller" lost his hand after it was trapped in a snare, Ngogo, Kibale National Park, Uganda.
Picture courtesy of Kevin Langergraber.

From the BBC (thanks to Cleve H and Dieter L for the link!)
Wild chimps outwit human hunters

Wild chimpanzees are learning how to outwit human hunters. Across Africa, people often lay snare traps to catch bushmeat, killing or injuring chimps and other wildlife. But a few chimps living in the rainforests of Guinea have learnt to recognise these snare traps laid by human hunters, researchers have found. More astonishing, the chimps actively seek out and intentionally deactivate the traps, setting them off without being harmed. The discovery was serendipitously made by primatologists Mr Gaku Ohashi and Professor Tetsuro Matsuzawa who were following chimps living in Bossou, Guinea to study the apes' social behaviour.

Snare injuries to chimps are reported at many sites across east and west Africa where chimps are studied, with many animals dying in the traps. However, very few snares injuries have been reported among chimps studied at Bossou, which is unusual as the chimps live close to human settlements and snares are commonly laid in the area.

Now primatologists know why.

While researching the chimps, Mr Ohashi and Prof Matsuzawa, of the Primate Research Institute at Kyoto University, Japan, observed five male chimps, both juvenile and adult, attempting to break and deactivate snares. On two occasions witnessed, the chimps successfully deactivated the traps set for them.

Wire noose
A typical snare, for example one made by the Manon people of Bossou, consists of a loop of iron wire connected by a vine rope to an arched stick, often a sapling. The sapling puts tension into the rope and once an animal passes through the wire loop, the trap is sprung and the sapling pulls it tight, around the neck or leg of an animal. Such traps cause indiscriminate damage, ensnaring any and all animals that come into contact with them.

But male Bossou chimps have worked out how to outwit the hunters and deactivate the traps. "They seemed to know which parts of the snares are dangerous and which are not," Mr Ohashi told the BBC.

In the journal Primates, the researchers describe six separate cases where chimps were observed trying to deactivate snares. Mostly, the chimps grasped the snare stick with their hands, shaking it violently until the trap broke. Sometimes a chimp lightly knocked the sapling that holds the snare, before grasping it to break the trap. But in all cases, they avoided touching the dangerous part, the wire loop.

Life-saving skills
"We were surprised when we found this behaviour," says Mr Ohashi. "This is the first report of chimpanzees breaking snares without injury." The chimps' actions may also reveal something important about how chimps learn. Often, chimps acquire new talents by trial and error. For example, when trying to crack nuts, they might strike one stone onto an anvil stone and miss the nuts all together. Or they might use their hands to strike the nut, which is ineffective. But the Bossou chips couldn't have learned how to deactivate the snares this way, as one mistake could be fatal. "The observations indicate that chimpanzees can learn some manners without trial and error," says Mr Ohashi.

The researchers speculate that the chimps may have learnt how the snares work by observing them over time, and this information has been passed down generations. During one case, a juvenile male watched an adult male deactivate a snare, before then moving in to handle it once it was safe.

The researchers caution that snares remain a significant threat to wild chimps, and they are leading conservation efforts to scan the forest for the traps and remove them. They also say that chimps in other regions do not appear so far to have also learnt how to outwit human hunters in this way.

Ohashi G and Matsuzawa T (2010) Deactivation of snares by wild chimpanzees. Primates
DOI: 10.1007/s10329-010-0212-8

Snare injuries to chimpanzees (Pan troglodytes) have been reported at many study sites across Africa, and in some cases cause the death of the ensnared animal. However, very few snare injuries have been reported concerning the chimpanzees of Bossou, Guinea. The rarity of snare injuries in this study group warrants further consideration, given the exceptionally close proximity of the Bossou chimpanzees to human settlements and the widespread practice of snare hunting in the area. Herein we report a total of six observations of chimpanzees attempting to break and deactivate snares, successfully doing so on two of these occasions. We observed the behavior in 5 males, ranging in age from juveniles to adults. We argue that such active responses to snares must be contributing to the rarity of injuries in this group. Based on our observations, we suggest that the behavior has transmitted down the group. Our research team at Bossou continues to remove snares from the forest, but the threat of ensnarement still remains. We discuss potential ways to achieve a good balance between human subsistence activities and the conservation of chimpanzees at Bossou, which will increasingly be an area of great concern in the future.

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