Giraffes are the perfect example of nature's creativity. They are so popular because not only
do they look cool on their own, but also because their simplicity can represent many other things.
Giraffes are generally the tallest animals in the world and can easily look up into your house.
They have necks that weigh about 600 pounds, too! The legs of a giraffe are also six feet long.
The back legs look shorter than the front legs, but they are about the same length.
A giraffe's heart is two feet long and weighs about 25 pounds. And its longs can hold 12 gallons
of air. Its closest, relative is the okapi, a giraffe has a lot of space between its chest
and head, which is probably the reason so many people wonder if the unique animal has two hearts.
National geographic confirms that these gentle giants are the tallest land mammals in the world.
Their necks are six feet long on average, which is why they need powerful cardiovascular systems.
Back to our question, what do giraffe say when they communicate?
Cows, moo, lions roar and dogs bark? But for many years, it's been assumed that except for
the occasional snort giraffe spent most of their lives in a tight-lipped silence.
New research from a group studying animal sounds at the university of Vienna suggests giraffes
might not be so quiet after all, they spend their evening humming.
It's not clear what tune they're humming, but it's important in social structure.
For decades zookeepers reported occasional snorts as the only sounds their charges made.
The conventional explanation was that the long necks of drafts caused their taciturn
nature. Giraffes do have larynx voice box, but perhaps they couldn't produce sufficient airflow
through their 13 foot long four-meter trachea to vibrate their vocal folds and make noises.
The researchers suspected the reason no one heard gaffe communication was because the
sound frequency was too low for humans to hear. Elephants and other large animals use an ultra-low
frequency rumble for long distance communication. Why not? Giraffes? So, they recorded giraffes at
three zoos compiling more than 938 hours of giraffe sounds over an eight-year period.
That's a lot and plowing through all that data seems to have worn on the researchers a bit.
In their paper, they note “exploring giraffe vocal communication turned out to be time consuming,
tedious, and very challenging. We strongly suggest developing an automatic system that
helps analyze a great amount of acoustic data. What made it so very tiresome was the researchers
didn't listen to the recordings, they visually examined them. They were looking for specific
patterns of low frequency sounds with harmonic structure. They found them and the pattern is
distinctive. The humming sounds only occurred at night and the average hum was about 92
Hertz in frequency, which isn't infrasound, but still on the low end for human hearing.
When the researchers played the sounds back to giraffe keepers and zoom managers, they'd
never heard them before. Giraffe’s have excellent vision, so their primary means of communication
is thought to be visual signals during daylight hours. As prey animals, it also makes sense
that they might not want to make loud noises that can attract the attention of predators.
But when vision is impaired at night, low frequency humming might be a great way to
make sure the herd stays together. I wasn't able to reach the researchers themselves,
but I did talk to Christopher Basu of the Royal veterinary college university of London
about humming giraffes and anatomy. He told me the giraffe larynx, which includes the vocal folds.
The things that vibrate to make noise is similar to the horse. Giraffes have the correct hardware
to make vocal noises, but they just don't or we thought they didn't until this new research.
The scientist calculated the relationship between vocal fold, length and sound production, and
giraffe humming fell roughly where it should have. Giraffes actually hummed a bit more vigorously
than predicted, which suggested some very interesting questions about their 13-foot trachea
to Basu. “To my knowledge, no one has ever measured air speed when giraffes exhale!
it would be a fantastic experiment. You'd have to persuade a giraffe to blow into a straw.”
What are giraffes saying with their nocturnal humming? We don't know! The new research
identified the sounds but provides no context for matching them to behaviour since giraffes
only hum in the dark. Matching the sound production to what's happening in a giraffe
society is the next step and will require some fairly high-level night vision instrumentation
and some really dedicated researchers to plough through reams of giraffe data.
Maybe in this case, they are humming because we don't know the words.
But why the humming? Meredith Bashaw at ‘The Franklin and Marshall college’
of Lancaster Pennsylvania says that she can imagine a few potential roles for this humming.
“It could be passively produced like snoring or produced during a dreamlike state, like humans
talking or dogs barking in their sleep.” She says. “Alternatively, it could be a way for giraffes
to communicate with each other in the dark, when vision is limited to say, Hey! I'm here.”
She adds, unfortunately Stoger says she and her colleagues were not able to observe the
giraffe's mid hum. So, we don't know about the behaviours associated with the sounds
but vocalizations and other species with similar social structures, no one to convey
information about things like age, gender, sexual arousal, dominance, or reproductive. She says.
John Doherty at Queens university Belfast studies giraffes in Samburu reserve in Northern Kenya. “I
have once come across audible vocalization reminiscent of the recordings again in a
captive giraffe,” he says, but in this case, the giraffe was clearly disturbed
by a husbandry procedure being carried out on its calf in a separate but visible enclosure.