"PHILADELPHIA == 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.
"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 travelling 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 communicate. (...) 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 junctions of trails and it was clear that the lead group was leaving markers for those who followed. (...) Sometimes, she said, intersections would be marked by large leaves pointing in the direction of travel. (...)
"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 resting trees."
(((bruces remarks: It seems hard to describe bonobo trail blazing as anything less than a "medium." While bonobos are not extinct, it seems quite plausible that our extinct protohuman ancestors also left "little notes in the vegetation." While paleolithic notched bones (see Working Note 3.00) are demonstrably 100,000 years old, the medium of trail blazing may well be several million years old and quite possibly pre-dates the human race.)))