Chimps Making Spears & Using
them for Hunting/Killing
(Top Posts - Science - 022307)

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Source: Iowa State University
Date: February 23, 2007
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Chimpanzees in Senegal are regularly making
and using spears to hunt other primates -- without
human assistance -- according to research led
by an Iowa State University anthropologist.

That study, funded by the National Geographic
Society, is the first to report habitual tool use by
non-humans while hunting other vertebrates.

Tia, who Professor Pruetz reports is an adoles-
cent female chimp who displayed the tool-use
hunting behavior frequently.


Jill Pruetz and Paco Bertolani ... documented 22
cases of the chimps fashioning tools to use in
hunting smaller primates in cavities of hollow
branches or tree trunks.


"We came upon the discovery quite unexpectedly,"
said Pruetz. "There were hints that this behavior
might occur, but it was one time at a different site.
Then I talked to my project manager (Bertolani)
and he told me that he saw a female hunt with
tools. When he looked through original data that
was collected, we realized he had other evidence
and observations of them probably doing the same
thing. While in Senegal for the spring semester,
I saw about 13 different hunting bouts. So it really
is habitual."

Chimpanzees forcibly jabbed tools into hollow
trunks or branches multiple times and smelled
and/or licked them upon extraction. Only two of
the 22 reported cases were seen as playful
-- in the case of an infant male -- or exploratory
in nature.

In all other cases, chimps were judged by the
researchers to use such force in inserting the
tool that prey within the tree could have been
injured. They witnessed just one case in which
a chimpanzee extracted a bushbaby -- a smaller
primate -- through use of the spear.

Females lead tool-assisted hunting

Despite the fact that hunting is predominantly
an adult male chimpanzee activity, only one
adult male (of 11 males in the community) was
observed in the tool-assisted hunting. The
reported incidents included one adult female,
one adult male, three adolescent females,
two adolescent males, one juvenile female,
one juvenile male, and one infant male.

"In the chimp literature, there is a lot of discus-
sion about hunting by adult males, because
basically, they're the only ones that do it -- and
they don't use tools," said Pruetz. "Females
are rarely involved. And so this was just kind
of astounding on a number of different levels.
It's not only chimps hunting with tools, but
females -- and the ones who hunted the most
with them were adolescent females.

"It's classic in primates that when there is a
new innovation, particularly in terms of tool
use, the younger generations pick it up very
quickly. The last ones to pick up are adults,
mainly the males," she said. "This is because
immatures learn from the ones they are most
affiliated with, their mothers."

They authors conclude that these findings sup-
port a theory that females might have played
a role in the evolution of tool technology among
the earliest humans. Those technologies included
hunting-related behavior, in addition to gathering-
related activities.

"The combination of hunting and tool use at Fon-
goli, behaviors long considered hallmarks of our
own species, makes the population especially
intriguing," they wrote.

"The observation that individuals hunting with tools
include females and immature chimpanzees sug-
gests that we should rethink traditional explana-
tions for the evolution of such behavior in our own
lineage. Learning more about the unique behaviors
of chimpanzees in such an environment, before
they disappear, can provide important clues about
the challenges facing our earliest ancestors."


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