26 September 2020 | New Scientist | 19AnimalsThe heavy cost of
clothes washingMILLIONS of tonnes of tiny
microplastics have been shed
from our clothing into the
environment over the past
seven decades or so, according
to an analysis of the impact of
clothes washing. Between 1950
and 2016, an estimated 5.6 million
tonnes of such particles have been
emitted – half in the past decade
(PLoS One, doi.org/d9d5).
“By mass, the amount ofSleep’s role seems to
change in toddlersWHY do we sleep? The answer may
depend on your age, according to
research that suggests the main
role of sleep shifts at the age
of around two-and-a-half.
Newborn babies sleep a lot, and
this gradually reduces as they get
older. To find out why sleep alters
as the brain develops, Van Savage
at the University of California,
Los Angeles, and his colleagues
collected published data on brain
activity and size and sleep duration
across different age groups.
They used this information to
build a model of how these aspects
might be expected to change as we
grow. This allowed them to swap
in different figures to test various
ideas. For example, if the brain
is learning during rapid eye
movement (REM) sleep, this
would lead to a prediction that
the duration of REM sleep is linked
to aspects of brain development,Neurology^ PollutionDURING a rainstorm on 29 February,
two giraffes were killed by lightning
in Rockwood, a conservation area
in South Africa. While it may seem
unsurprising that the world’s tallest
animal faces this risk, scientists had
never described this occurrence in
any detail until now.
“It came as a bit of a surprise
to me because the whole day was
quite quiet in weather, and suddenly
there was this big storm,” says Ciska
Scheijen, a conservation scientist at
Rockwood who had been following
a group of eight giraffes in the area.
Scheijen says she immediately
suspected something was wrong
with the herd after the storm, as she
could only see six of the animals.
Rockwood ranger Frans Moleko
Kaweng went out to investigate and
found the oldest and tallest giraffe
of the herd, the matriarch, lyingdead with a wound on top of her
head. It appeared as if one of her
ossicones – the horn-like knobs
on a giraffe’s head – may have
acted as a lightning rod in the storm.
“It looked like the ossicone broke
off,” says Scheijen.
The body of a younger female lay
7 metres away. She was probably
killed by a side flash from the
strike – in which the lightning
jumped from the matriarch – or
by ground current, as she was
standing close to the other giraffe
(African Journal of Ecology,
DOI: 10.1111/aje.12785).
“It’s possible that this happens
more often to giraffes than other
species because of their height.
But I think more research is needed
to see if this has an effect on the
natural selection of giraffes,” says
Scheijen. Joshua Rapp LearnThe knobs on a giraffe’s
head can prove deadly
microfibres that has been emitted
to the ocean is equivalent to about
7 billion fleece jackets just being
thrown into the ocean,” says Jenna
Gavigan at the University of
California, Santa Barbara. Similar
amounts of shed microfibres have
ended up on land, mostly cropland.
Microfibres – strand-like
particles of microplastics – come
from washed clothes, particularly
synthetic fabrics. Researchers are
only beginning to learn how these
particles might effect ecosystems,
but they can be ingested by small
marine organisms, such as
plankton, and work their way
through the food chain.
Microplastics often act as
“sponges” for toxins, says Gavigan,
and are able to transport a variety
of chemicals into an animal’s
digestive tract, some of which
are likely to be harmful. The
particles are also thought to cause
physical damage once ingested
by animals. We don’t yet know
how detrimental these tiny
fibres might be to humans. JHwhich can then be tested against
published findings.
The group found that most
of the brain processes associated
with learning occur during REM
sleep, and that this appears to be
the most important function of
sleep generally in young infants,
who get much more REM sleep
than adults (Science Advances,
doi. org/ghb7x7).
But there seems to be an abrupt
shift in toddlers. “Before two-and-
a-half, sleep is mainly about...
rewiring the brain to learn and
grow,” says Savage. But after this
age, the main function of sleep
appears to be the repair of any
damage to the brain. “I was
surprised that it was such a sharp
transition point,” says Savage,
who likens the sudden change
to water freezing into ice.
The findings need to be
confirmed by studying how
children’s brains change over
time, says Rebecca Spencer at
the University of Massachusetts
Amherst. Jessica HamzelouSH
UT
TE
RS
TO
CK
/M
ITC
HE
LL^
KR
OG
PL
AINPICTURE
/GLAS
SHOUSE
/DERRICKGOMEZNews In brief