6 | NewScientist | 8 September 2018NEWS & TECHNOLOGY
Michael MarshallMUMMIFIED penguins have been
found littering the ground in
Antarctica. The birds seem to have
died during two bouts of extreme
weather over the past 1000 years.
Such conditions are expected to
become more common as a result
of climate change, making mass
die-offs more likely.
The birds were found on Long
Peninsula, in east Antarctica, by
researchers led by Liguang Sun
at the University of Science and
Technology of China in Hefei.
It isn’t unusual to find dead
penguins, but those on Long
Peninsula – mainly chicks – are
especially numerous, with up to
15 per square metre and hundreds
overall. “They consist of well-
preserved dehydrated mummies,”
the researchers write in a paper.
All are Adélie penguins
(Pygoscelis adeliae), which only
live in Antarctica. They currently
breed in the Antarctic summer
at about 250 sites, forming huge
colonies near the coast.
To find out what happened on
Long Peninsula, Sun’s team used
carbon dating to estimate the ages
of the corpses. They also studiedsediments, which contain
excrement and nest material.
They found that penguins have
lived there for at least 3900 years,
but most of the deaths occurred
in two periods, about 750 and
200 years ago. The colonies were
abandoned afterwards each time,
as little new sediment was laid
down in later centuries.
The cause seems to have been
unusually heavy snow or rain over
several decades. The team found
evidence of floods that carriedsediment and corpses downhill,
and signs of erosion (Journal of
Geophysical Research:
Biogeosciences, doi.org/ctj9).
Rain is a lethal threat, says Yan
Ropert-Coudert of the French
National Centre for Scientific
Research. “The chicks especially
are not made for wet weather,”
he says. Hypothermia is a risk.
Meanwhile, snow makes it hard
for parents to find pebbles to
make nests, and if it melts the
meltwater can drown chicks.
The cause of the wet weather
was probably a shift in the
Southern Annular Mode, a pattern
of winds in the Southern Oceanthat can send extra damp air to
east Antarctica. Climate change is
likely to make this more frequent.
Adélies are widespread, so can
handle occasional disasters, says
Steven Emslie at the University of
North Carolina Wilmington. But
they face increasing pressures. In
April, Emslie published a study of
the largest modern Adélie colony,
at Cape Adare. “Sea level rise is
going to displace hundreds of
thousands of penguins there and
at Cape Hallett within the next
30 to 50 years, as those beaches
are gradually inundated,” he says.
Ropert-Coudert has detailed
the disastrous 2013-14 breeding
season, when no chicks survived
in a major colony on Petrel Island
in east Antarctica. Unusually
heavy snowfall killed them,
combined with weak winds that
failed to break up the sea ice,
preventing adults from catching
enough food. And it wasn’t a one-
off. “In 2016-17 we had a second
massive breeding failure in the
same place,” he says.
According to the International
Union for Conservation of Nature,
Adélie penguins are at low risk of
extinction. But Ropert-Coudert
says repeated breeding failures
on Petrel Island are a bad sign.
The solution is to limit climate
change as much as possible,
he says. We could also set up
protected areas to “prevent other
threats from superimposing on
the climate ones”. ■Graveyard is a bad
omen for penguins
HIROYA MINAKUCHI/MINDEN PICTURES/FLPA“ Dark matter density should
increase as you move to
the centre of a galaxy, but
some didn’t get the memo”THE dark matter in small galaxies has
been giving cosmologists a headache.
Blowing up a few stars may provide
the solution.
Dark matter is thought to make
up most of the matter in the universe
and should be found mixed in with
the regular matter of galaxies. The
standard model of cosmology, called
lambda-CDM, predicts that the densityStar explosions
could explain
misfit galaxies
of this dark matter should increase
as you move towards the centre of a
galaxy, but some dwarf galaxies didn’t
get the memo: they have a constant
density of dark matter.
That might seem a minor wrinkle,
but if it can’t be explained within
lambda-CDM, it could deal a blow to
our understanding of dark matter.
“The implications of these very
subtle measurements are large
so people have argued a lot over
them,” says Marla Geha at Yale
University, who wasn’t involved
in the latest work.
Star formation is one potentialexplanation. Some stars are born
after old ones die in explosive
supernovas, which send matter flying.
Bursts of such star formation in small
galaxies might blow some dark matter
towards the edges, smoothing out
the distribution.
Justin Read at the University of
Surrey in the UK and his colleagues
used measurements of the mass at
the centres of dwarf galaxies to testthis idea. They picked out samples of
two different types of galaxy, eight
that stopped forming stars long ago,
and eight that are still forming stars
or only stopped relatively recently.
They found that the galaxies with
higher rates of star formation had less
dark matter in their centres, pointing
to a more uniform distribution. That
matches up with the idea that star
formation moves mass towards
the edges of the galaxy, which then
shifts the dark matter outward.
It’s a good sign for lambda-CDM,
if the result stands up (arxiv.org/
abs/1808.06634). Leah Crane ■Climate change threatens the
Adélie penguins of Antarctica