In brief–

sensory organ, the squirrels

wagged their tails but didn’t

bother to warm them up first.

Tests with robotic squirrels

based on taxidermists’ models

confirmed that a warmed squirrel

tail made rattlesnakes more likely

to act defensively, Rundus and

Owings report in Proceedings of

the National Academy of Sciences

(DOI: 10.1073/pnas.0702599104).

It taught us to focus on the

perceptual world of the animal

we’re studying rather than

thinking only of human

perceptions, says Rundus.

and his supervisor Donald

Owings of the University of

California, Davis, wondered how

it might affect the snakes’

interaction with the adult

squirrels. So Rundus used an

infrared camera to spy on

squirrel-snake stand-offs. He

saw the adults’ tails heat up,

presumably due to increased

blood flow, when they were

warning rattlers away – making

the squirrel appear larger to the

snake’s infrared organ.

Confronted with a gopher

snake, which has no infrared

A SWISS woman who fell off her

bicycle has yielded a unique

insight into how auditory

hallucinations are generated.

The woman suffered damage

to the part of the brain where

speech is generated and could

speak only in short, stunted

words and sentences. Five months

later, when she suddenly

developed epilepsy, she began

“hearing” voices with the same

speech impediments as herself.

“She initially heard her own

voice speaking aloud, then the

voices of hospital staff,” says

Daniela Hubl at the University

Hospital of Psychiatry in Bern,

Switzerland, a member of the

team that treated her. “They had

the same speech impediments as

she did. It proves that the voices

were generated in the language

areas of the patient’s own brain.”

The hallucinations disappeared

when the woman received drugs

to control her epilepsy ( The

Lancet , vol 370, p 538).

Hubl believes the case is unique

and supports more strongly than

ever the scientific consensus that

“voices” and other hallucinations

experienced by people with

conditions like schizophrenia are

generated within their own brains.

Ghostly speech impediment

EXOTIC foreign males are most

attractive – for female spotted hyenas

at least. And this female preference

for the unusual is what drives young

males to leave their clan and seek out

another pack.

Nearly 90 per cent of male

spotted hyenas (Crocuta crocuta)

leave their birth clan and disperse

to pastures new, but until now it has

never been clear what drives them

away. Is it that they are avoiding

competition for mates, trying to

preserve resources for the rest of the

pack, or avoiding inbreeding?

None of the above, say researchers

led by Oliver Höner of the Leibniz

Institute for Zoo and Wildlife Research

in Berlin, Germany, who have been

monitoring all 400 hyenas in the

Ngorongoro crater , Tanzania, since 1996.

They have shown that the females are

running the show, driving males to

leave by selectively mating with

immigrants from outside the pack

(Nature, DOI: 10.1038/nature06040).

“We found that female hyenas

prefer to mate with males who have

immigrated into their pack, or who

were born into the clan after the

female was born,” says Höner. By

following this simple rule, females

avoid inbreeding and help to maintain

the genetic health of the pack.

YOU would think that right after the

big bang, the universe would have

been pretty hot. In fact it looks like

things were a lot cooler than you

might imagine.

Cosmologists believe that the

universe went through a rapid

period of expansion known as

inflation . But, says Pedro Ferreira at

the University of Oxford, they usually

ignore the effects of temperature on

inflation – and that’s a big mistake.

“At the violent temperatures we

assume are around at the time,

everything would be moving

rapidly,” he says. “Space-time itself

would be bubbling and boiling.”

Ferreira and João Magueijo,

currently at the Perimeter Institute

in Waterloo, Canada, realised that

any such thermal “noise” would

have been amplified during

inflation. If the noise had been too

loud, it would have disrupted the

formation of galaxies and left behind

huge imprints on the cosmic

microwave background today.

Because we don’t see such

imprints, while we do see large

galaxies and clusters, we have a

clue to the temperature of the early

universe, says Ferreira. The pair

calculated that at the end of

inflation, 10-32 seconds after the big

bang, the maximum temperature

would have been about 11,000 °C

(www.arxiv.org/abs/0708.0429).

“That’s extremely cool – not the

zillions of degrees you’d expect,”

says Magueijo.

CALIFORNIA ground squirrels

have evolved a subtle trick to scare

off rattlesnakes – but it remained

invisible to biologists until they

looked at the animals through an

infrared video camera.

Young California ground

squirrels (Spermophilus beecheyi)

are easy prey for snakes, so

protective adults harass the

predators while puffing up their

tails and wagging them.

Rattlesnakes have an infrared

sensing organ for detecting the

body heat of small mammals.

Graduate student Aaron Rundus

NASA

/STS

CI/A

URA

JEAN

MIC

HEL L

ABAT

/ARD

EA

Hot tails are key to snake-squirrel stand-offs

16 | NewScientist | 18 August 2007 www.newscientist.com

Male hyenas are the leavers of the pack

How the big bang chilled out

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