Gibbons and other nearby gibbons saw it too.

HOO KNEW?
one
Phforce
sometimes make A chorus of soft hoo calls came from the
soft ‘hoo’ calls Esther’s team returned to the forest in 2009
trees. Then the apes began throwing
while lounging to collect more data. In all, they recorded
sticks at the intruder. But they didn’t
in trees hundreds of calls made by the gibbons.
have to worry.
They also jotted down notes about when
Although the figure looked like a big
and where each vocalisation was used.
cat, it was actually a scientist covered in
Esther analysed each recording on a
tiger-print fabric who was crawling on
computer to determine its length and its
all fours! “The experiment showed that
frequency (how high or low the sound is). Engineer and National Geographic
these calls can be used as a danger
She discovered that each kind of
signal,” Esther says. Emerging Explorer Topher White was
vocalisation was used for a different
The team also placed a pretend bird upset that a forest in Indonesia was
situation. For instance, one type of hoo call
of prey in tree branches near one of being ravaged by illegal logging, leaving
announces that the gibbons have found
the gibbons’ hangout spots. When the
apes saw the bird, they let out hoo calls
fruit. And mates make another one before the gibbons there without a home.
belting out their loud duets as a way of Topher then realised that he could
that were even quieter than usual. “This
telling each other “Let’s sing!” help protect their habitat by attaching
surprised us because we thought that all
Following on from Esther’s research, her recycled mobile phones to trees!
hoo calls sounded the same,” Esther says.
colleagues have now identified 26 basic
The team’s findings indicated that gibbons
sounds like ‘wa’, ‘hoo’, ‘oo’ and ‘waoo’ – and The phones were programmed to
make different hoo calls for different pick up the sound of a logger’s
they’re gradually trying to decipher ‘words’
predators. “We learned that there’s more chainsaw. They then transmitted the
and ‘phrases’, like we have in English (have
to these calls than anyone had realised.” audio and their location to a control
a go below!). Maybe one day they’ll be able
to produce a ‘dictionary’ of white-handed centre, which sent

ak
gibbon ‘language’. park rangers to the

to spe One thing’s certain – these gibbons really

n!
scene. Topher’s

Learn
are giving scientists something to talk about.

o
system is now being

gibb
used in rainforests
Get your lips around worldwide.
If there were a
these six gibbon phrases… gibbon call to say
“Wooo-hoo-hoo-hoo-wa-wa”* Look out! Big cat! thank you, Topher
SCIENCE SPY TRICKS “Hoo......hoo......hoo......hoo” Look out! Eagle!
“Hoo-hoo-hoo-wooooo-wooOOOO-WOOOOOOOOOOOOO-wooo-woo-woo-woo-woo”
would be hearing
it a lot!
A fake Listen to me/check me out! (the ‘great call’, a phrase that’s specific to female gibbons)
bird of “Wa-wa-wa-WA-WA-wa-wa” She’s my mate and I’m guarding her, so stay away! Topher White mounts
prey (the male’s immediate response to her ‘great call’) a solar-panel-powered
placed “Waa-hoo-wa-waa-wa-wa” I’m a male gibbon and I’m with her mobile phone to a tree
near a “Wa-waa-waaa-hoo-waa-hoo” I’m a female gibbon and I’m with him
group of
Communication is key to gibbons’ survival, gibbons softer gibbon vocalisations known as * The smaller the writing, the softer the call
and they have many different vocalisations, causes hoo calls. “Families use hoo calls all the
or calls. Some are loud enough to echo an time,” Esther says. “But no one really
through their rainforest habitats in parts uproar knew what they were saying.” The
of Southeast Asia. But others are so soft sleuthing scientists finally located a

Up ins
that humans can barely hear them. few small groups of gibbons to spy on.
Until recently, little was known about these
quiet calls. But by using a combination Scientists LISTEN UP

arm
of technology and tricks, scientists have place a Since hoo calls are barely audible to
Lounging © Picture Alliance / Photoshot; Bird of prey, leopard-print blanket, microphone © Dr. Esther Clarke;

begun to crack the code to this language. clouded humans, the researchers brought along
Graphic © Chris Philpot; Topher White © Rainforest Connection; Hanging upside down © Alanna Collen.

leopard- a high-powered recording device that

CLOSE CALLS print blanket could pick up even the softest sounds.
In 2005, British ecologist Esther Clarke on a tree and And as the animals snacked on fruit,
led a team of scientists on a ‘spy’ mission listen for groomed each other and babbled away
Gibbons have the
in Khao Yai National Park, Thailand. the gibbons’ in the treetops, Esther quietly stood longest arms in
Their goal was to eavesdrop on white- response underneath, holding up a microphone. proportion to their
handed gibbons living in these woods. Over the next four months the team bodies of any other
The white-handed gibbon is one of 16 recorded gibbon ‘conversations’ for primate. Here’s what a
species in the gibbon family, a group up to an hour at a time. In addition to ten-year-old human
of tree-dwelling apes. The animals are making hoo calls while chilling out, the would look like if
known for having super-long arms that team suspected that gibbons created her arm-to-body
they use to move across branches. these vocalisations when they sensed
In the morning, mated pairs of white- a predator. To find out, Esther and her proportions were the
handed gibbons produce loud whoops colleagues used some unexpected tools same as a gibbon’s…
in unison. They belt out these 15-minute in their research kit…
ape anthems, known as duets, as a way
of telling others to back off their territory. FANCY DRESS
Hiking through the forest, the scientists One day a mother white-handed gibbon
A gibbon’s
could hear these booming cries. But was grooming her baby in a tree when
Esther Clarke strong arms
Esther’s team wasn’t there to study the an orange creature with black stripes allow it to hang
loud calls. They wanted to learn about eavesdrops on walked across the forest floor. Her mate
gibbon calls from branches

22 National Geographic Kids ngkids.co.uk 23