New Scientist 2018 sep

8 September 2018 | NewScientist | 17

THE Arctic is in hot water, literally.

Heat has been accumulating

rapidly in a salty layer 50 metres

down in a large part of the Arctic

Ocean. Currently, it is capped by

a less-dense layer of fresh water,

but the fear is that winds could

make this lid fall apart. If the two

layers mix, this could melt all the

seasonal sea ice above.

Mary-Louise Timmermans at

Yale University and her colleagues

discovered the heat time bomb

after analysing data on ice cover

and sea temperature, heat content

and saltiness at different depths

over the past three decades in the

Canadian basin, which is fed by

waters from the North Chukchi

Sea, north of the Bering Strait

between Alaska and Siberia.

The team found that the heat

content of the 100-metre-thick

salty layer had doubled over this

time. The root cause is global

warming, which has seen Arctic

surface temperatures rise by 2°C

from pre-industrial levels, leading

to record-low sea ice coverage.

With sea ice retreating, heat

absorption by surface waters has

increased fivefold in 30 years, the

team found. Strong winds push

these newly warmed surface

waters at the Arctic fringes down

to the depths where they are now

accumulating under the ice

(Science Advances, doi.org/ctf4).

IN BRIEF

AGAMI PHOTO AGENCY / ALAMY STOCK PHOTO

Wolves may have influenced

when elk shed their antlers

EACH spring male elk lose their antlers so they can grow

back bigger and stronger to fight rivals for mates in

autumn. It turns out wolves may have helped shape the

evolution of this timing: if elk lose their antlers too soon,

their risk of ending up as wolf food rises. Too late and

they may fail to win a mate.

Matthew Metz at the University of Montana and

colleagues analysed 55 encounters between male elk

and wolves in Yellowstone National Park from 2004 to

2016. They found that elk that shed their antlers early
      were also the most vulnerable to wolf attacks.

In 18 cases wolves attacked a lone male, and the

presence or lack of antlers made no difference. But the

remaining 37 encounters involved attacks on groups of

two or more male elk, and wolves targeted stags without

antlers. Groups containing at least one antler-less animal

were 10 times more likely to be attacked (Nature Ecology

& Evolution, DOI: 10.1038/s41559-018-0657-5).

The findings may also apply to related species.

Elk don’t have a choice about when they shed their

antlers – it is probably linked to testosterone levels –

but shedding early seems to carry long-term benefits for

a potential short-term but fatal cost.

“We suggest that wolves – formerly everywhere across

the northern hemisphere – have shaped the timing of

when elk... shed their antlers,” says Metz.

Warm-water time bomb threatens Arctic

Opioid blocks pain

and addiction

A NEW opioid drug has been

shown to stop monkeys feeling

pain, without any apparent

addictive or harmful side effects.

Opioids such as morphine

stop pain, but can also be

addictive. In the US alone, more

than 46 people die daily from

overdoses of prescription opioids.

Mei-Chuan Ko at Wake Forest

University in North Carolina and

his colleagues have found that a

drug called AT-121 blocks pain by

activating two types of opioid

receptor in the brain. One is

the mu opioid receptor, the

pain-relieving receptor targeted

by many opioids. The other is

the nociceptin opioid receptor,

which blocks the brain’s

addiction-forming response,

while also providing pain relief.

The drug was 100 times as good

as morphine at reducing pain in

monkeys. No addictive properties

were seen (Science Translational

Medicine, doi.org/ctf3).

Serengeti shaped

by ancient herders

AFRICA’S Serengeti grasslands are

far from pristine works of nature.

In fact, their rich biodiversity

may owe more to cowpats from

livestock corralled overnight by

nomadic herders millennia ago.

Such dung has long been known

to provide hotspots of nutrients

in otherwise barren grasslands,

eventually enabling much richer

ecosystems to develop. It was

assumed that, on the Serengeti,

these spots – called grassy glades –

date back roughly 1000 years.

Fiona Marshall of Washington

University in St Louis, Missouri,

and her colleagues have shown

they may be much older. The

team sampled five sites in Kenya

and found evidence of dung and

richer soils dating back 3700 years

(Nature, doi.org/gd3zfb).