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Monkeys' "Do Not Disturb" Sign Posted on February 4, 2011
Monkeys have culture? Resist that eye roll. A group of mandrills at England's Colcester Zoo have been observed covering their eyes, possibly an example of a cultural development.
The "striking" gesture has been observed for at least ten years among the zoo mandrills--the world's largest monkey, according to a new study.
(Also see: "Monkeys That Floss With Human Hair Learn From Mom?")
The 23 mandrills in the group all cover their eyes, regardless of age or sex, sometimes for more than 30 minutes and while also raising their elbows in the air.
Laidre and colleagues believe the gesture arose from an individual and was copied by other mandrills, and eventually developed its own meaning.
A mandrill covering its eyes.
Scientists aren't sure exactly what it means, but the rough translation might be "leave me alone."
According to the study, "the gesture might have a locally respected meaning," possibly to "inhibit interruptions as a 'do not disturb' sign operates."
Because the gesture emerged naturally, independent of human involvement, and has now lasted a full generation, it could be considered a cultural behavior, the authors say.
Mark Laidre, an integrative biologist at the University of California, Berkeley, studied 19 other mandrill communities in North America, Europe, and Africa--the monkey's native continent--and found no other evidence of eye-covering.
The mandrills will cover their eyes for more than 30 minutes.
Laidre told me by email that he also queried several long-term primate observers, and none have seen the behavior.
"While I imagine that other primate species might occasionally cover their eyes, the behavior does appear fairly unique," he said.
"And at least in mandrills, very few of the hundreds of individuals I have observed around the world do this behavior. So it is obviously special in mandrills, and may not be very common in other species either."
Monkey-gesturing study published February 2 in the journal PLoS ONE.
--Christine Dell'Amore
Photos courtesy Mark Laidre, University of California, Berkeley
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Man in his arrogance assumes he is THE most intelligent life on Mama Earth, and always seems surprised when other creations residing here with us display signs of culture, emotions, high intelligence, self-awareness, etc., as well.
I watched an interesting documentary a good awhile back about monkeys who use rocks to break nuts...but it's not just about using the rocks- the monkeys literally taught each other...I could not find the exact info as contained in that documentary, but I found something similar to it:
Capuchin monkeys not only have the capacity to use tools, they also know which tool is best for the job at hand, according to a new study. Researchers observed capuchin monkeys in the wild testing out different stones and consistently settling on the heaviest, sturdiest stone to crack open palm nuts. Although anecdotal reports existed before, the new study is the first to systematically document tool use in capuchin monkeys. Because capuchins last shared a common ancestor with humans approximately 35 million years ago, the team writes, the capacity for stone-tool use evolved earlier than thought [New Scientist].
Researchers studied eight wild capuchins living in a forested area of Brazil. In several different trials, researchers planted two or three different rocks, of varying hardness, size, and weight, near where the monkeys were feeding. The choices ranged from crumbly sandstone to tough quartzite, with some artificial stones that the monkeys would not normally encounter also thrown in the mix. Capuchins chose the most effective stone for cracking nuts more than 90 percent of the time in four conditions. That figure fell slightly to 85 percent when the monkeys selected from artificial stones of the same size and different weights [Science News].
The trick to effective nut-cracking, it seems, is to choose the heaviest rock. “When a capuchin touched a light tool it almost immediately discarded it and switched to another stone to check if it was heavy enough,” [New Scientist] says researcher Elisabetta Visalberghi. It was clear that the monkey were not simply choosing a rock at random. They consistently selected the heavier rock even though weight was not always visually obvious. The researchers found that if two or three stones looked identical, the capuchins would pick a stone at random and test it by lifting, moving, or tapping it [New Scientist].
Other than in humans, such tool selectivity had been shown only in chimpanzees, which are closely related to humans. Capuchins are much more distant relatives. “Here we showed that a species removed from humans 35 million years ago is capable of being extremely selective in terms of tool use,” Dr. Visalberghi said. “I’m far from arguing that this is extremely special and unique. Perhaps it is simpler than we expected” [The New York Times]. Writing in Current Biology [subscription required], the researchers do argue that the capuchin’s tool-selection reveals planning and forethought. Other researchers believe such behavior can be learned through trial-and-error, and that the monkeys need only to develop a simple association between heavy stones and successful nut-cracking.
Nevertheless, it’s likely that capuchins and early humans both discovered gadgets through play. “You do a behavior in your free time, you play with objects, and by doing it over and over, discover something that turns out to be useful,” said Visalberghi. “They spend a lot of time on the ground, like early humans probably did. It’s possible that tool use is the byproduct of being on the ground where stones, anvils and nuts are, with time to explore, play and try new things” [Wired News].
Elephants have culture as well, as do dolphins and orcas.....
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A group of mandrills at England's Colcester Zoo have been observed covering their eyes, possibly an example of a cultural development.
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