Chimpanzees have favourite tools for hunting ants
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It is well known that chimpanzees use tools, much like humans.
But now experts have found that West African chimps in Guinea have a favourite tool set for catching their staple food of ants.
They search far and wide to find a spindly shrub with straight shoots, called Alchornea hirtella, which makes the ideal tool to hunt aggressive army ants, new research reveals.
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West African chimps have a favourite tool set for catching their staple food of ants. They search far and wide to find a spindly shrub with straight shoots, called Alchornea hirtella, which makes the ideal tool to hunt aggressive army ants (pictured)
The plant provides the animals with two different types of tool - a thicker shoot for 'digging' and a more slender tool for 'dipping'.
When they have found an army ant colony, chimpanzees will dig into the nest with the first tool to aggravate the insects.
They then dip the second tool into the nest, causing the angry ants to swarm up it.
Once the slender shoot is covered in ants, the chimpanzees pull it out and wipe their fingers along it, scooping up the ants until they have a substantial handful that they eat in one motion.
This technique, called ant dipping, was previously believed to be a last resort for the hungry apes, which they only exploited when their preferred food of fruit couldn't be found.
But the latest study, based on over ten years of data, shows that army ants are a staple in the chimpanzee diet which are eaten all year round regardless of available sources of fruit.
This may be because the ants are a source of protein and fats, according to Kathelijne Koops from the University of Cambridge, who published the findings in the American Journal of Primatology.
'Ant dipping is a remarkable feat of problem-solving on the part of chimpanzees,' said Dr Koops.
'If they tried to gather ants from the ground with their hands, they would end up horribly bitten with very little to show for it. But by using a tool set, preying on these social insects may prove as nutritionally lucrative as hunting a small mammal - a solid chunk of protein.'
If Alchornea hirtella is nowhere to be found, the chimps will fashion tools from other plants, and they spend a long time looking for their preferred shrub.
Previous research has shown that chimpanzees will select longer tools for faster, more aggressive types of army ants.
The average 'dipping' tool length across the study was 25 inches (64cm), but some were selected that were 30 inches (76cm) long.
Dr Koops is investigating how chimpanzees acquire knowledge of such sophisticated techniques.
'Scientists have been working on ruling out simple environmental and genetic explanations for group differences in behaviours, such as tool use, and the evidence is pointing strongly towards it being cultural,' she explained.
'They probably learn tool use behaviours from their mother and others in the group when they are young.'
The research for the ant-dipping study - which took place in Guinea's Nimba Mountains - proved challenging, as the chimpanzees were not used to people.
When they have found an army ant colony, chimpanzees will dig into the nest with the first tool to aggravate the insects. They then dip the second tool into the nest, causing the angry ants to swarm up it
The team acted like archaeologists, studying 'exploited' ants nests to measure abandoned tool sets and 'sifting through faeces for ant heads'.
To study these illusive creatures further, Dr Koops set up cameras to film the chimps using the tools extensive video footage of the chimpanzees and their tool use.
She even filmed a chimp making a tool to investigate the camera.
Dr Koops said: 'This study is part of a big ongoing research project. The next stages will involve looking at social opportunities to learn: how much time do youngsters spend within arm's length of other individuals, how much time do they spend close to their mother, as well as innate predispositions to explore and engage with objects.'
'By studying our closest living relatives we gain a window into the evolutionary past which allows us to shed light on the origins of human technology and material culture,' she added.
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