Friday, February 23, 2007

Chimps make spears

A paper in Current Biology (see abstract below) reports on chimps that fashion spears and use them to get bush babies (small prosimians). The spears are made of branches that are slightly sharpened at the tip by knawing. It seems that they kind of poke and try to immobilize the bush babies in holes where they hide. They found this behavior to be most prevalent among females and immatures. This reminds me of a tv show I saw last night where captive male chimps did not attempt to make ketchup fishing tools nearly as much as females did. Is this because males are "too good" for this kind of "small time" food acquisition and are more interested in acquiring more substantial sources of food (hunting for monkeys)?
The authors make a case for the importance of studying these savannah chimpanzees living in Senegal, since they inhabit a environment similar to our EEA (environment of evolutionary adaptedness).
There are movies in the 'supplementary data" section.

Savanna Chimpanzees, Pan troglodytes verus, Hunt with Tools

Jill D. Pruetz, and Paco Bertolani

Current Biology, In press

Abstract: Although tool use is known to occur in species ranging from naked mole rats [1] to owls [2], chimpanzees are the most accomplished tool users [3, 4, 5]. The modification and use of tools during hunting, however, is still considered to be a uniquely human trait among primates. Here, we report the first account of habitual tool use during vertebrate hunting by nonhumans. At the Fongoli site in Senegal, we observed ten different chimpanzees use tools to hunt prosimian prey in 22 bouts. This includes immature chimpanzees and females, members of age-sex classes not normally characterized by extensive hunting behavior. Chimpanzees made 26 different tools, and we were able to recover and analyze 12 of these. Tool construction entailed up to five steps, including trimming the tool tip to a point. Tools were used in the manner of a spear, rather than a probe or rousing tool. This new information on chimpanzee tool use has important implications for the evolution of tool use and construction for hunting in the earliest hominids, especially given our observations that females and immature chimpanzees exhibited this behavior more frequently than adult males.

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