“Man, ants are cool.” — Eric KLavinS
Great Dane minds don’t think alike
By Laura Sanders
Female dogs might have a leg up on
males when it comes to detecting the
unexpected. In an experiment designed
to mess with their furry heads, Fidos
appeared oblivious to a surprising outcome while Fidettes took note.
The results, published online April
27 in Biology Letters, highlight that, like
humans, animals display sex differences
in how the brain works.
In the study, researchers led by Corsin
Müller of the University of Vienna tested
50 pet dogs, including poodles, Austra-
lian shepherds, golden retrievers and
mutts. The team designed an experiment
to test whether the dogs would notice a
ball that inexplicably grew or shrank. In
some trials, for instance, a tennis ball
would roll behind a screen, and after a
short wait, a larger ball would appear on
the other side. (Human babies begin to
detect this violation of how the world
works during the first year of life.)
So far, the researchers can’t tell if male
dogs really don’t perceive the difference,
or do detect it but don’t care, Müller says.
Whether a dog had been neutered
didn’t seem to make a difference in the
experiment, suggesting that the brain
differences behind the effect were established early in the dogs’ development
and were not a result of sex hormones
circulating in adult dogs at the time of
the test.
Researchers don’t know why this sex
difference exists. Müller and his colleagues don’t think strong evolutionary
pressure on a dog ancestor has a role.
But neuroscientist Timothy Koscik
of the University of Iowa points out that
females need to effectively nurture offspring, and that might have provided
strong pressure to set up this behavioral difference. “If you’re going to draw
any line between males and females,” he
says, “that’s probably the most obvious
and most meaningful one to draw.”
Research shows how whole
colonies build rafts to safety
a colony to survive,” says study coauthor
Teamwork keeps
fire ants floating
And the rafts are flexible enough to
withstand some jostling. Mlot and his
colleagues filmed the emergency raft
construction by dropping up to 7,000 ants
into water. No matter how many bugs
clung to the rafts, these
structures adopted the
same 8-millimeter-thick
“pancake” shape. When
the team plucked ants
off the top, others from
the bottom crawled up.
“Each ant is operating
on a few simple rules of
engagement,” Mlot says.
With these simple
rules, ants have been
able to build extraor-
dinary structures, says
Eric Klavins, a computer
scientist at the University of Washington
in Seattle. By studying how ants interact,
engineers may be able to design robots
that run on smaller processors and can
work in concert to build things like
emergency bridges.
Nathan Mlot of Georgia Tech. Their dou-ble-decked rafts — about half the ants
float on the bottom holding the rest up — can bob
along for weeks.
“Man,” Klavins says, “ants are cool.”
The ants’ seafaring
success comes down to
both small and big prop-
erties. On the small scale,
single ants can float, at
least to a degree, similar
to a pin or a water-strid-
ing insect. When wet,
fire ants can also capture
tiny air bubbles, probably
thanks to the thin layers
of hair covering their
bodies, giving these intrepid mariners
additional buoyancy. On the large scale,
ants weave together so tightly by biting
onto their neighbors’ legs that water can’t
sneak through the cracks.
Groups of fire ants keep
afloat with cooperation
and some basic physics.
By Daniel Strain
Fire ants know how to survive a flood:
They turn their bodies into life rafts.
A new study explores the physics that
keeps waterborne colonies of fire ants,
sometimes containing tens of thousands
of bugs, afloat. Linked together, the ants
form a watertight seal that keeps them
from drowning, engineers from the Georgia Institute of Technology in Atlanta
report online April 25 in the Proceedings
of the National Academy of Sciences.
Fire ants (Solenopsis invicta), an invasive species around much of the globe,
are ready for disaster. When their Brazilian homes flood, entire colonies take to
the waves. “They have to stay together as
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May 21, 2011 | SCIENCE NEWS | 11
