April 25, 2013 [NY Times]
Monkeys Are Adept at Picking Up Social
Cues, Research Shows
If you are eating lunch in Pittsburgh or Dallas, you
might grab a sandwich and a Snapple to go. But should you get transferred to
Paris, you will probably eat like the French: multicourse sit-down lunches
plus a glass of wine.
But it turns out people are not the only ones
who make monkey-see-monkey-do cultural shifts. Monkeys, and apparently
several other species, do, too.
In a clever, groundbreaking study
Thursday in the journal Science, researchers showed that when Vervet monkeys
roam, they act in when-in-Rome fashion.
Wild Vervet monkeys, trained
to eat only pink-dyed or blue-dyed corn and shun the other color, quickly
began eating the disliked-color corn when they moved from a pink-preferred
setting to a blue-is-best place, and vice versa.
The switch occurred
even though both corn colors were equally accessible, side-by-side in open
containers. Scientists said the monkeys relinquished their color convictions
because they saw the locals eating the hated hue.
addressed a long-contentious question among animal experts: is animal
behavior determined only by genes and individual learning, or can animals,
like humans, learn socially?
�Culture was thought to be something
only humans had,� said Carel van Schaik, an evolutionary anthropologist at
the University of Zurich who was not involved in the study. �But if you
define culture as socially transmitted knowledge, skills and information, it
turns out we see some of that in animals. Now this experiment comes along
and I must say it really blew me away.�
He added: �Imagine you�ve
just learned to eat pink corn and for a while blue corn was really bad, but
then you move to an area where it�s the opposite and basically you wipe your
slate clean. You think, �Oh, these locals, they must know what�s the best
Other studies have found similar learning abilities in
social animals. In the same issue of Science, researchers reported that by
observing others, humpback whales learned to whack the water with their tail
fins to attract prey.
But while previous research often relied on
anecdotes, observations or animals in captivity, the monkey study documented
social learning in wild animals.
�We long believed that cultural
transmission was important,� said Frans de Waal, a primatologist at Emory
University who did not take part in the study. �But I never thought it would
be at the scale where the results would be so strong.�
scientists set out pink and blue corn in adjacent Tupperware containers for
four groups of wild monkeys in neighboring regions in a South African
reserve. A study leader, Erica van de Waal, a researcher at University of
St. Andrews in Scotland, said she wanted to use red and blue, shades monkeys
are known to see because they are the colors of male Vervet genitalia. But
South African grocery stores stocked mostly blue and pink food coloring
because people use them for cakes celebrating girl and boy birthdays.
After trying vinegar and chilies to make corn taste bitter, researchers
settled on soaking corn in acrid-tasting aloe leaves. Pink corn was �aloe
treated� for two groups; blue for the other two. Soon, monkeys in each group
consistently rejected the colored corn soaked in aloe leaves.
several months, researchers stopped treating the corn with aloe, but monkeys
continued eating only the color that had never been made bitter. Dominant
monkeys never sampled the disliked color; subordinate monkeys might, but
only if dominants were hogging the liked color.
Baby monkeys, which
received no color training, instantly ate only what their mothers ate, even
squatting on the other color, �totally ignoring that there was an edible
color under their feet,� Dr. van de Waal said.
Most strikingly, when
male monkeys migrated from a different-colored region, they ate the local
color. The one exception was a blue-is-best male who entered a pink area
with no dominant male, took control and continued eating blue corn. But he
�might be a stupid male that had too much testosterone and was just not
looking at what the others are doing,� Dr. van de Waal said.
said researchers hoped to test if social learning applied to other
behaviors, like mating calls and grooming.
Experts said that to
survive, species must balance experimentation with conservatism, so it makes
sense that monkeys would develop rigid aversions to a once bitter-tasting
color, and drop that aversion in another community. Both behaviors have
advantages for survival, saving learning time and avoiding deadly risks.
�I don�t expect it in bacteria or slugs,� Dr. van Schaik said. �But in
these long-lived species that are social, you�re actually willing to give up
what you know, drop that memory like a hot potato, because those in the
other place do something else.�