AND ORANGUTANS HAVE SOMETHING IN COMMON
by Whit Gibbons
October 6, 2003
used to be a trait thought to be exclusive to humans, but apparently
only because humans were the ones doing the reporting. Research on some
of the great apes, which also include gorillas, orangutans, and gibbons,
has provided evidence that chimpanzees pass cultural behavior down from
one generation to the next. A recent study has shown that orangutans
also have a cultural side.
is the transmission of socially learned knowledge or tradition to succeeding
generations, and not surprisingly, humans were once believed to be the
only species in which cultural differences occurred between populations.
Recently, variation in chimpanzee behavior in different geographic regions
has been cited as evidence of culture. This past year Carel P. van Schaik
of Duke University and colleagues documented that the behavior of orangutans
also varies geographically.
are large, some males reaching about 200 pounds, with extremely long,
powerful arms. The big, intelligent apes have reddish hair that usually
looks a bit shaggy. They were formerly native to Southeast Asia, where
they are now extinct, presumably because of being hunted by humans.
Today the last of the orangutans occur naturally only in the rainforests
on the two large islands of Borneo and Sumatra. By one report, more
than 300,000 orangutans were alive in the wild in 1900 compared to fewer
than 20,000 today. If the report is true that more than 2,000 orangutans
disappear from the wild each year, the species will be extinct before
today's elementary school children reach college. Illegal removal of
orangutans for the pet trade remains a problem for the species but,
as is true for most wildlife, the greatest threat is habitat destruction.
investigators examined wild orangutan populations at six sites, four
in Borneo and two in Sumatra, to determine what forms of tool using
and other specific behaviors were present in the different populations.
The scientists considered evidence of culture to be situations in which
most or all of the orangutans at one site exhibited a type of behavior
that was not practiced by any orangutans at the other five sites. Orangutans
anywhere were capable of the behavior, but only those who had learned
it from their parents or members of their own population actually exhibited
it. Such findings support the position that cultural evolution had occurred.
The investigators classified 19 behaviors as "very likely cultural
variants," which included using leaves to wipe the face, using
a branch as a swatter against bees and wasps, and using a leafy branch
to scoop up water from a tree hole. Many of these were common behaviors
in one population but were completely absent or rare in the other populations.
For example, a customary habit throughout one of the populations from
Sumatra was to poke into tree holes with a tool to obtain insects. But
the orangutans in the Sumatra population were not more clever than other
orangutans; using a stick as a tool is behavior learned from watching
others, so now everyone at that site does it.
scientists also noted that similarities in cultural traits among orangutan
populations, as measured by behavioral repertoires, decreased with increasing
geographic distance. That is, the closest population to another one
was more likely to be similar in special behavioral traits than the
population farthest away. An individual who moves from one population
to another, and may bring a new skill or useful behavior that can be
learned by others, is more likely to find its way to a nearby population
than to a more distant one.
scientists also found that some groups of orangutans had more social
contact than other groups, in which individuals were more solitary.
Not surprisingly, the former had a greater number of learned behavioral
activities that would be more readily passed on as a result of greater
social interaction. Such observations further support the idea that
certain behaviors in orangutans have been passed on culturally. I feel
certain that future studies with gibbons will show that they also are
highly cultured great apes.
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