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WINTER 2014
air before diving underwater. As
they descend, the water pressure
increases, compressing the air
trapped in the feathers. At a depth
of 80-100 feet the air volume has
shrunk by as much as 75 percent.
When they are ready to surface, the
birds depress their feathers, locking
them around the reduced volume of
air. As they speed vertically toward
the surface, the air trapped in the
plumage expands and pours through
the feathers.
The structure of the feathers
is highly complex, and the pores
through which the air is pushed are
so small that the bubbles are initially
very tiny. They’re so tiny, in fact, that
they form a coat on the outer surface
of the feather. This coat of small air
bubbles is the key to the penguin’s
strategy for avoiding leopard seals.
The bubbles act as a lubricant,
drastically reducing drag and enabling
the penguins to reach lift-off speeds.
Davenport and his colleagues
described how if a seal is present,
the penguins use their “bubble
propulsion” strategy as they rocket
to the surface, often clearing the
ice edge by several feet before
crashing onto the ice and giving out
an “umph” and a squeak, having
knocked the air out of themselves.
Over a period of three weeks I
spent hours watching these amazing
“flightless” birds soar as they exploded
out of the water in an unforgettable
show of power and grace. The
seemingly simple adaption of using
air bubbles to reduce the friction
of water, increase speed and burst
out of the water is a central element
of emperor penguins’ predator-
avoidance strategy. To witness
first-hand the relationship between
emperor penguins and their predators
and observe the strategies they have
developed to avoid predation was
the opportunity of a lifetime and one
that could only happen in a place
as insulated from human impact as
Antarctica. However, despite the cold
continent’s remoteness, the future
of the emperor penguin is intimately
linked not to the leopard seal but to
human dependence on fossil fuels.
As we continue to dump carbon
dioxide into the atmosphere, the
biggest threat to emperor penguins
is the possible breakout of a large ice
mass that blocks the way between the
penguin colony and the ice edge.
— Paul Nicklen
Although they move awkwardly on land, emperor penguins are the picture of grace
in the water. Below: Not every penguin makes it back onto the ice.
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