Bonobos Use Symbols to Mark Jungle Trails
2/14/98
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Title: Bonobos Use Symbols to Mark Jungle Trails
Source: The Associated Press via CNN
Status: Copyrighted, contact source for reprint permissions
Date: 2/14/98
PHILADELPHIA (AP) -- Researchers studying apes in the wild have found that
African bonobos use complex trail markers to silently communicate in the dense
tropical forests where they live along the Congo River.
The discovery is contrary to the belief of many scientists that apes lack the
brain structure for the use of symbolic language in complex communications,
said E. Sue Savage-Rumbaugh of Georgia State University.
"The evidence is there," Savage-Rumbaugh said Saturday in a presentation at the
national meeting of the American Association for the Advancement of Science.
"We only have to look at it."
Bonobos, apes that closely resemble chimpanzees, live in very dense forest with
only faint trails. They live in bands of more than 100 and each night rest
together in trees.
During the day, the apes separate into small groups and forage for food, often
traveling for miles and moving silently to avoid predators.
And yet, when the day ends, members of the band find their way back together at
a new resting place.
Savage-Rumbaugh said this behavior shows that the animals must communicate.
Just how they do it has been a mystery until now.
Crushed plants provide clues
She said that in following the animals through the forest, she noticed that
whenever a trail crossed another trail, the lead group would stamp down
vegetation or rip off large leaves and place them carefully.
"What they are doing is leaving little notes in the vegetation," she said.
"Those notes are signals about where they are going to go."
Savage-Rumbaugh said the plants were disturbed only at the junctioons of trails
and it was clea that the lead group was leaving markers for thosewho followed.
Frequently, said Savage-Rumbaugh, a path intersection would have a single
smashed plant and two smashed plants would mark the selected trail. Sometimes,
she said, intersections would be marked by large leaves pointing in the
direction of travel.
In muddy areas where footprints were obvious, no plants were disturbed. When a
tree trunk crossed the path, there were smashed plants in front and behind. If
plants were disturbed only in front of the trunk, the animals then walked on
top of the trunk, following it to another trail, she said.
"These cues are not left at arbitrary points, but rather at locations where the
trails split or cross and where an individual following might be confused as to
the correct direction to take," she said.
When all the members of the band travel together, the trail markings are
absent, said Savage-Rumbaugh.
To prove her discovery, Savage-Rumbaugh said she twice followed the trail signs
far behind groups of the apes. At the end of each day, she found her way to the
reassembled band's new nesting trees.
Possibility of verbal communication still unknown Savage-Rumbaugh said it is
impossible to study verbal communications between bonobos in the wild because
they only vocalize when they are together in the trees. But captive bonobos,
she said, have been easily trained to respond to verbal language and to point
to symbols that have specific meanings.
"I don't know what they do with their speech in the wild, but given that they
learn it so easily in captivity there is a good chance that they are using it
in the wild," she said.