Amplify’d from penguinology.blogspot.com
An Emperor penguin leaps from the water (Image: Blue Planet, BBC)
In fact, taking to the air, for even a brief instant, is actually a
vital strategy penguins employ to avoid being eating by predators such
as leopard seals or orcas.
Now scientists have worked out the secret technique that penguins use
to get airborne. It involves wrapping their bodies in a cloak of air
bubbles – and it turns out to be the same technique that engineers use
to speed the movement of ships and torpedoes through water.
Another interesting aspect of the discovery is that it was made by
scientists examining in minute detail footage shot for the programme Blue Planet, a landmark natural history series filmed by the BBC’s own Natural History Unit.
short, squat birds, which tend to live in the colder parts of the
southern hemisphere, are renowned for their waddling walks and flapping
flippers – which are famously great for swimming, but useless for
flying.
But many species of penguin do take to the air.
Due to their body shape, and poor climbing ability, it is difficult
for penguins to haul themselves ashore, especially onto rocky
shorelines. And it can be almost impossible for a penguin to haul itself
out from the ocean onto sea ice.
Emperor penguins create bubble trails (image: Blue Planet, BBC)
through and briefly get airborne to clear the rocks or ice shelf, and
land on their breast.
Smaller species, such as Adelie penguins, can leap 2-3 metres out of the water, landing unscathed onto broken rock. Bigger species, such as Emperor penguins (the
largest of all), reach heights of 20 – 45 cm, but that is enough for
them to leap out of holes in the ice and clear the ice’s edge.
But one aspect of this leaping behaviour has long puzzled biologists.
As the birds swim toward the surface, they trail a wake of bubbles
behind them. No one knew where these bubbles come from, or why there are
there.
Five years ago, that began to change when a group of biologists met
in a pub in Cork, the Irish Republic, before the start of a scientific
symposium.
from Bangor University in Gwynedd recalled how he’d seen a wildlife
film in which penguins trailed bubbles in this way and asked his
colleague Professor John Davenport, of University College Cork, if he knew why they did so.
Adelie penguins leap high (image: photolibrary.com)
Together they obtained footage from the BBC of its Blue Planet
series, which filmed breaching penguins for its Frozen Seas episode.
when the coast is clear, they trail a wake of bubbles before leaping
from the water)
The scientists slowed down this footage, analysing the speeds and
angles of emperor penguins exiting the water, developing a basic
biomechanical model of what was going on.
discoveries. The bubbles of air being trailed by the penguins weren’t
coming out of the birds’ lungs via the beak.
Instead, they were coming from the birds’ feathers.
The researchers also realised that these air bubbles form a “coat”
around the birds’ bodies as they rocket toward the surface at speeds of
19km an hour.
To investigate further, the three scientists teamed up with Professor
Poul Larsen from the Danish Technical University in Lyngby, who brought
his expertise in mathematics and fluid mechanics to the research.
The four scientists have now just published the results of their study.
indeed what enables the penguins to get air as they leap onto land.
Penguins have great control over their plumage, Professor Davenport tells me.
They raise their feathers to fill their plumage with air, then dive
underwater. As the birds descend, the water pressure increases,
decreasing the volume of the trapped air. At a depth of 15-20 metres,
for example, the air volume has shrunk by up to 75%.
The penguin then swims vertically up as fast as it can, and the air in the plumage expands and pours through the feathers.
“Because the feathers are very complex, the pores through which the
air emerges are very small so the bubbles are initially tiny. They coat
the outer feather surface.”
Crucially, this coat of small air bubbles acts as a lubricant,
drastically reducing drag, enabling the penguins to reach lift-off
speeds.
By placing a layer of air around a ship’s hull, or torpedo, for
example, designers can dramatically reduce drag, and speed up the boat
or weapon’s passage through the water as a result.
But “this process has never been thought of before as having a biological role,” says Professor Davenport.
The penguins also appear to have overcome one other issue that
blights naval architects trying to exploit “air lubrication” underwater.
The moment before lift off (image: Blue Planet, BBC)
also have a major slowing effect if the bubbles reach a ship or
torpedo’s propeller. That’s because the propeller starts pushing against
air not water.
However, a penguin’s flippers, its means of propulsion equivalent to
the propeller, are held outside of the bubble clouds, so they are not
affected.
See this Amp at http://bit.ly/oIueoZ
