Something to crow about: birds with tools of trade
Date: March 28 2003
By Roger Highfield
A remarkable colony of inventors has emerged on an isolated Pacific
island. They can fashion tools out of materials scavenged from the
rainforest. They can even customise a tool for a given job.
Early studies showed crows to be almost human-like in their use of
tools, with technological features that match the stone and bone-tool
cultures that emerged among primitive humans between 2.5 million and
But the anthropocentric still took solace from the fact that only
humans were thought to have the brain power required for cumulative
technological evolution. This is the skill for innovation that two
million years ago took our ancestors from creating flakes of flint, for
use in cutting, to honing knives, blades, arrowheads and axeheads.
Now this "unique" attribute of humans has also turned out to be a
flattering delusion. A new study shows that the crows of New Caledonia
are inventive. With their evolving leaf tools, the birds have levered
man off his pedestal.
The creative skills of the birds are described this month in the
Proceedings of the Royal Society by Dr Gavin Hunt and Dr Russell Gray,
of the University of Auckland. They have spent the past decade studying
feathered technology in the islands of Grande Terre and Mare in the
South Pacific archipelago of New Caledonia.
After an intensive field survey of local crow industry - sampling 21
sites and 5550 leaf tools - the scientists found that the birds rip the
barbed leaves of the pandanus (screw pine) tree to fashion three
distinct types of tools for grub and insect extraction: wide, narrow
Because the strap-like leaves are reinforced by tough parallel fibres,
the latter tapered design is best made in steps. With precision beak
work, the crow nips the leaf, then rips along the fibres. Next it makes
another cut and tears again, repeating until it has a tool with usually
two, three or four steps.
The scars on the remains of leaves used by the crows revealed
similarities in the cutting and ripping used for each of the three
basic tool designs, and their different but overlapping geographic
All the designs are found around Riviere Bleue, at the end of Grand
Terre, suggesting that the first prototype leaf tool was invented there
to winkle bugs out of crannies.
The ability of the birds to innovate is further shown by their making
of other tools, such as hooks, and how they do not rely on one raw
material: as well as pandanus, the birds make hooks out of twigs and
similar materials. They often strip a twig of leaves, and sometimes of
bark, and cut it off just below a shortened offshoot to create a hook
to weedle out bugs.
Professor Alex Kacelnik, a fellow of Pembroke College, Oxford, praised
the study as "extremely important". It complements his own research
which has turned Betty the New Caledonian crow into a star by revealing
her to be the first animal, other than man, to show a basic
understanding of cause and effect.
Betty began making tools after her partner, an old male called Abel
(now deceased), snatched away a hook made for her by the researchers,
forcing her to make her own from garden wire to fish out morsels from a
She wedged the end of the wire into the base of the food tube and
turned her head to form the hook.
What amazed the researchers was that she could even adapt her hooks if
they were not up to the job, something that even chimpanzees were
unable to do.
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