EVER SINCE the pioneering studies of Jane Goodall, primatologists have
known that chimpanzees use tools – for instance, sticks to extract termites
from a nest. Now, it seems, this tool-using behaviour may be more complex
than people had thought. Wild chimpanzees may bring more than one tool to
bear on a particular task, and apply those tools in a precise sequence.
Stella Brewer and Bill McGrew of the University of Stirling have studied
wild chimpanzees (Pan troglodytes) in the Gambia. Their observations are
the first of a chimpanzee actually using a ‘tool set’ (Folia Primatologica,
vol 54, p 100).
Brewer and McGrew observed a chimpanzee named Katie who was trying to
gain access to a source of honey. Katie used four different tools in all.
The first was a large branch with a sharp end. She used this as a ‘chisel’
to jab at and crumble the strong waxy covering of the bees’ nest. Katie
then discarded this tool in favour of a shorter, thinner stick, which was
more sharply pointed. This she used to chisel deeper and more accurately
into the hole she had made.
Next, Katie took up a third tool – a green branch, which was about a
centimetre in diameter and which she had trimmed to a length of about 30
centimetres. She inserted this into the hole and then pushed it with considerable
force to puncture the nest’s seal. Finally, she dipped a thin green vine
through the hole and used this to extract quantities of dripping honey from
the nest.
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Zoologists have managed to induce such a ‘sequential’ use of tools –
in which the use of each tool depends on the action of its predecessor –
in chimpanzees in captivity. But Brewer and McGrew are the first to report
such a ‘tool set’ being used by a wild chimpanzee.
