lab rats are more likely to eat their young if their cages are cleaned often

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HOW many pygmy hippos are left

in the wild? It’s hard to estimate

numbers of elusive animals, but a

new census method should make

it possible to uncover the secrets

of even the shyest.

Conservation biologists use

automatic cameras triggered by

infrared sensors to record the

presence of animals such as

pygmy hippos or deer that tend

to flee or hide from humans.

With most species, though, it is

impossible to tell whether the

camera is recording a few

individuals many times or many

individuals a few times.

Now Marcus Rowcliffe at the

Institute of Zoology in London

and his colleagues have adapted

equations for the random motion

of gas molecules to help them

estimate the population density of

a species from the frequency with

which animals are photographed.

The only other information they

need is how fast the animals move.

The researchers tested their

method in an animal reserve on

two species of deer and a type of

wallaby, and found the population

sizes calculated matched the

actual populations in the park

(Journal of Applied Ecology, DOI:

10.1111/j.1365-2664.2008.01473.x).

Treat a hippo like

a gas molecule

AS THE old adage has it, cleanliness

is next to godliness, but it also has

sinister consequences for lab rats:

they are much more likely to

cannibalise their young if their

cages are frequently cleaned.

Charlotte Burn at the

University of Oxford and Georgia

Mason at the University of Guelph

in Ontario, Canada, found that

nearly twice as many pups were

eaten in cages cleaned twice a

week as in those cleaned

fortnightly (Applied Animal Behaviour Science, DOI: 10.1016/

j.applanim.2008.02.005).

Cannibalism was most likely if the

cages were cleaned soon after the

pups were born.

Burn notes that cannibalism in

rodents is not unusual; mothers

sometimes eat unhealthy young

to conserve energy for raising

healthy ones. But while this might

be normal behaviour, it could be

disruptive in a research context

The findings suggest that

cleaning their cages disrupts the

rats’ ability to recognise their kin,

according to Volker Rudolf at Rice

University in Houston, Texas.

Burn says that scent is the key to

rats being able to recognise their

pups. She suggests minimising

the handling of very young

pups to avoid interfering with

the scents that bond their parents

to them.

It is also important, she says,

to avoid introducing foreign

scents into the rats’ cages. For

example, lab technicians should

avoid handling several rats one

after another.

Finally, Burn advises, cleaning

the rats’ cages should not “stress

the parents with loud noises or

physical disturbance”.

Cleaning cages makes a meal of lab rats’ own young

RED hair, freckles and pale skin make

you sun sensitive, but genes, not

pigmentation, may be the ultimate

guide to who is most likely to get

skin cancer after sitting in the sun.

Genes for light hair and skin

and the risk of skin cancer tend to

go hand in hand. For instance, the

same mutations in a gene called MC1R

that cause red hair and freckles also

greatly increase the chances of

getting melanoma if you sunbathe.

But not all such genes are equally

affected by sunlight.

Researchers led by Karí

Stefánnson of Decode Genetics in

Reykjavik, Iceland, have identified

a mutation in a gene called ASIP that,

like MC1R, is linked to red hair and

freckles and increases the likelihood

of getting skin cancer (Nature,

DOI: 10.1038/ng.161). Interestingly,

though, this ASIP variant doubles

the risk of melanoma even in sun-

starved Icelanders, indicating that its

skin cancer effect is less dependent

on sunlight than MC1R ’s.

“In Iceland you can avoid

sunlight because it is so rare,” says

Stefánnson. In contrast, his team

found that having the MC1R variant

had little effect on Icelandic people’s

risk of developing skin cancer,

indicating that its effect was highly

dependent on exposure to sunlight.

“It doesn’t look like it’s just

pigmentation,” agrees geneticist

Stuart MacGregor of the Queensland

Institute of Medical Research in

Brisbane, Australia.

Sun, skin and the wrong set of genes

FOR skiers and snowboarders there is

no business like snow business. But in

the Alps winter sports may be doing

no business at all in years to come.

In the late 1980s, there was a

dramatic step-like drop in the amount

of snow falling in the Swiss Alps. Since

then, snowfall has never recovered,

and in some years the amount that

fell was 60 per cent lower than was

typical in the early 1980s, says

Christoph Marty at the Swiss Federal

Institute for Snow and Avalanche

Research in Davos. He has analysed

snowfall trends spanning 60 years

and adds that the average number of

snow days over the last 20 winters is

lower than at any time since records

began more than 100 years ago.

The future of winter tourism in

the region is looking grim. “I don’t

believe we will see the kind of snow

conditions we have experienced in

past decades,” he says.

Previous studies have suggested a

decline in the region’s snowfall but

Marty’s analysis is the first to take in

10 years of new data from 34 stations

between 200 and 1800 metres above

snow level. The work will appear in

Geophysical Research Letters .It’s hard say whether this marks

any kind of tipping point in terms of

climate change, says Marty. “But from

the data it looks like a change in the

large-scale weather pattern,” he adds.

Alps are no go without snow

18 | NewScientist | 24 May 2008 www.newscientist.com

In brief–

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