Source: The Mercury, 16 January, 1997, p.67

Stroppy penguins
fight for the roost

Torgersen Island

Research  is revealing some 
surprising and, at times, un-
savoury secrets about penguins, 
those elegantly-feathered symbols
of Antarctica.

   They steal each other's
eggs and come close to
pecking each other to death
to defend their territory at
remote, windswept nesting
sites such as tiny Torgersen

   The new research also
suggests penguins' pugnacity
at their nesting sites could be
linked to testosterone, the
male hormone that rages
through penguin blood early
in the mating season and
which, in humans, is
popularly associated with
aggressive behaviour.

   The difference is that in
penguins, hormonal
secretions are all calibrated
by natural selection to give
the birds' fluffy, grey
offspring the best possible
chance at surviving in a
harsh environment,
researchers said.

   "The thing that most
impresses me about the
penguins is how attached
they are to their young and
to their nesting sites," said
Carol Vleck, an Iowa State
University zoologist.

   Blood samples from Adelie
penguins taken by Vleck hint
at a hormonal drive behind
the eccentric, at times violent
behaviour of penguins early
in their breeding cycle, followed
by a more nurturing phase
when chicks hatch and
testosterone levels crash.

   "It's extraordinary to see
how much personality they
have," Vleck said, standing
among hundreds of jabbering,
wide-eyed penquins on the
island near the US National
Science Foundation's Palmer
Station research site.

   "They make a sudden shift
from aggression and
defending their territory early
in the breeding season to
raising and nurturing their
chicks later on. And you can
see hormonal changes behind
that shift."

   The Iowa State study is
one of several on little-
understood aspects of
penguins, who are
notoriously hard to study
because they spend most of
their lives at sea and breed in
a tough climate.

   Recent research into an-
other species, the Emperor 
penguin, has shown that 
males incubate the eggs for
nine weeks in temperatures
ranging down to minus 60 degrees
during winter and the penguins
can dive to 630 metres making
them possibly the world's
deepest-diving birds.

   The Adelie penguin's
breeding cycle starts in
October when the winter ice
pack starts melting and the
male and female come ashore
to court and stake out

   The female lays two
tennisball-sized eggs in a
nest made of pebbles and
heads out alone to the open
sea to fatten up on krill, a
shrimp-like crustacean.

   The male, meanwhile, stays
at home to keep the eggs warm
and protect them from skuas,
hawk-like birds that terrorise
nesting sites.

   When the female returns, the
male, who has been fasting for
up to a month, leaves to feed
and the two then alternate
every couple of days in
incubating the eggs until the
chicks hatch by late December.

   By March, when winter
starts its onslaught, the young
are ready to fend for

   The penguins few months on
land, when daylight lasts about
22 hours and food is abundant,
give researchers a brief look at
how they live and interact, not
always in a positive way.

   Penguins have been known
to steal eggs from their
neighbours or usurp another's
nest, take over the chick and
raise it: odd behaviour since "it
makes no evolutionary sense
at all," Vleck said. Males and
females constantly defend their
territory or try to expand it at
neighbours' expense,
sometimes violently.

   Vleck once saw penguins
peck a neighbour nearly to
death to try to carve out more
nesting territory. One of the
attacking birds was found to
have unusually high levels of

   Penguin parents cannot
leave their offspring alone for
a second lest they be eaten by
skuas or their territory stolen
by neighbours. They nest in
extremely close quarters,
apparently because a closer
concentration makes it harder
for flying predators to grab
eggs and chicks.

   A 50-square-metre plot can
have hundreds of nesting pairs
and there is fierce competition
among penguins for the best

   Not all penguins manage to
find a mate. Those that do not
"just kind of wander around
looking forlorn", while others
make a nest and go through all
the motions of incubating
eggs even though there are
none, a practice that "could be
some kind of practice for next
year," Vleck said.

   She sees all this behaviour as
part of a kind of internal
programming to raise young, a
genetic automatic pilot that
keeps them sitting on the nest
for days even if the eggs have
been eaten by a skua or stolen
by a neighbour.

   She and her research team
draw blood from about 300
penguins each season,
catching them with nets and
drawing bright-red blood from
the bird's neck.

   Studies of penguin
populations could give crucial
data into climate changes in

   For example, a decline in
Adelie penguins and an
increase in another species, the
Chinstrap, could be an indirect
result of a slight warming in
the Antarctic over the past 30
years, said William Fraser, an
ecologist from Montana State
University and chief scientist
at Palmer Station.

   Adelie penguins prefer to
spend the winter on pack ice,
which has become scarcer as
the climate warms, while
Chinstraps prefer open water,
potentially giving them an
advantage in the race for food,
he said.


Where to next?

Student Questions for this article
Teacher Discussion of this article
Index - Related articles
Index - Number
Main Index - Numeracy in the News