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bagged 10 adult males during the
mating season and four pregnant
females in the month that
followed. Then goshawks took
nine juveniles (The American
Naturalist, DOI: 10.1086/507714).
“The males were so obsessed with
sex they couldn’t watch for
predators,” Hoogland says.
If, as Hoogland believes,
predators were behaving more as
they would when people are not
around that’s bad news for the
endangered prairie dog. “What
really happens when we’re not
there?” he asks.
most vulnerable. So what was
different in 2005?
He believes that the prairie
dogs’ predators were behaving
more normally because they had
become used to the presence of
people. Usually foxes, coyotes and
badgers “will go elsewhere when
they see us”.
Prairie dogs live in colonies
and warn each other of predators
so they can dive into burrows
for protection. In 16 previous
seasons, his team had seen only
22 prairie dogs swiped by
predators. But last year a fox
IF YOU are trying to commit
something to memory, take a nap.
Even a short daytime snooze
could help you learn.
A good night’s sleep is known
to improve people’s ability to
learn actions such as mirror
writing. REM sleep, when most
dreaming occurs, is thought to be
particularly important.
The role of sleep in factual
learning has been less clear. Now
Matthew Tucker at The City
University of New York and his
colleagues have shown that even a
nap with no REM sleep can help.
Volunteers were told to
memorise pairs of words (a test of
factual learning) and to practise
tracing images in a mirror (action
learning). When they were tested
straight afterwards and 6 hours
later, those who had been allowed
a nap of up to 1 hour before the re-
test scored 15 per cent better in the
factual test than the non-nappers,
but no better in the action test
(Neurobiology of Learning and
Memory, vol 86, p 241).
“Traditionally, time devoted to
daytime napping has been
considered counterproductive,”
the researchers say. It now seems
sleep is “an important mechanism
for memory formation”.
Snooze your way to high test scores
YOUNG, old and sick animals are
usually the ones that end up as
lunch – though not, it seems, if
you’re a prairie dog in Utah. Last
year it was the turn of healthy,
adult males.
“This has really made me
rethink everything,” says John
Hoogland of the University of
Maryland Center for
Environmental Science in
Cambridge.
More than 30 years of studying
prairie dogs had given Hoogland
no reason to question the notion
that the weakest animals were the
CORB
IS
NOAA
Sex mad prairie dogs fall prey to bold foxes
www.newscientist.com 23 September 2006 | NewScientist | 17
ON 29 August 2005, as hurricane
Katrina was rumbling towards New
Orleans, a seismic hum more than
1000 times the strength of the
average volcanic tremor was felt
nearly 3000 kilometres away in
southern California. Its source was
the hurricane itself.
Hurricanes create large ocean
waves, which send energy pulsing
through the Earth as they pound the
shoreline. To determine the power of
Katrina’s seismic waves, Peter
Gerstoft of the University of
California, San Diego, and colleagues
analysed the signals recorded by a
network of 150 seismic stations in
southern California just before
Katrina hit the Louisiana coast.
They used a method known as
beamforming, which preferentially
picks up signals from a particular
direction, to decipher the seismicity
generated by Katrina (Geophysical Research Letters, vol 33, p L17805).
Seismic surface waves, which
travel through the Earth’s crust, were
detected 30 hours before the
hurricane made landfall, while body
waves, which bounce down into the
mantle, arrived some 18 hours later.
“The body waves had travelled down
to 1100 kilometres inside the Earth,”
Gerstoft says. This is the first time
that a hurricane’s seismic signal has
been detected so far away.
Katrina’s waves felt in California
DOGS not only protect your home, they
can protect your health as well. Young
children turn out to be less likely to
suffer a bout of gastroenteritis if there
is a pet in the house.
Jane Heyworth at the University of
Western Australia in Crawley and her
colleagues observed nearly a thousand
4 to 6-year-old children in South
Australia for six weeks, noting
incidences of nausea, diarrhoea and
vomiting. Children who had a cat or
dog in their household were 30 per
cent less likely to show these
symptoms than children living in
homes without pets (Epidemiology and Infection, vol 134, p 926).
This came as a surprise. “It is a
commonly held view that dogs and
cats are a source of gastroenteritis, but
our results do not support that,”
Heyworth says. She suggests that
children living with pets are exposed
to low levels of bacteria when young,
and that this could prime their
immune systems to handle such bugs.
A previous study showed that
children living with at least two
animals were up to 77 per cent less
likely to develop allergies (New Scientist, 7 September 2002, p 24).
There is also some evidence that pet
owners may be less likely to suffer
from heart disease and depression.
This doesn’t necessarily mean
parents should rush out and buy a pet.
“The benefits need to be weighed
against the drawbacks,” Heyworth
warns. “After all, dogs can bite.”
Household pets keep kids healthy
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