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Reach out and branch someone.

Reach out and branch someone

It's early in the morning in the rain forest surrounding the Wamba Research Station in Zaire. A pygmy chimpanzee climbs down from its nest in the trees and methodically searches the underbrush. It soon finds what it's looking for: a tree branch, which it noisily drags between the nesting tree and a nearby tree laden with fruit. The racket awakens another pygmy chimp, which joins its boisterous buddy for breakfast at the fruit tree.

Branch dragging, such as this early morning "wakeup call," is common among pygmy chimps at Wamba, says Ellen J. Ingmanson of the University of Washington in Seattle. Its frequent occurrence in a number of situations demonstrates sophisticated tool use and complex communication skills among wild pygmy chimps, she contends.

Ingmanson observed three groups of pygmy chimps, with a total population ranging between 30 and 10, from September 1987 through January 1988. Branch dragging was performed mainly by adult males, and occasionally by adult females and adolescent males. Chimps choose branches carefully; they are usually 6 to 7 feet long with a leafy end suitable for creating lots of noise in the underbrush.

Branch dragging is likely to take place during the chimps' daily treks through the forest, Ingmanson says. Adult males use the technique to get the group moving, indicate the intended direction of movement, signal a change in direction and hurry stragglers along.

For example, females take more time to eat than males and somtimes fall behind the group. Often, several males drop behind those who dawdle at a feeding site and drag branches in semicircles to herd them toward the main group.

"Very specific information is communicated through branch dragging concerning intention and direction of movement," Ingmanson notes.
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Title Annotation:Anthropology; branch dragging behavior of pygmy chimpanzee
Author:Bower, Bruce
Publication:Science News
Date:Apr 22, 1989
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