Koalas reallyarebuilt for life in the
treetops.Australia’s cuddly koala seems to have
evolved tree clambering abilities that rival
those of the apes and monkeys that never
made it to the continent.
Technically a marsupial – bearing
its young in a pouch like kangaroos and
wombats – Phascolarctos cinerus has
relatively long limbs with two thumb-like
digits on powerful grasping hands and feet.
And it is more comfortable in the trees than
on the ground.
Christofer Clemente, from the
University of the Sunshine Coast, and
colleagues were therefore curious to
know whether it uses the same movement
strategies as tree-dwelling primates.
As described in the Journal of
Experimental Biology, the researchers ran
experiments at Queensland Zoo’s Wildlife
HQ, filming six koalas in their semi-natural
enclosures using several high-speed cameras
synchronised to give a 3D reconstruction of
their movements.
This took a few months, because koalas
spend a lot of time sleeping. They also
moved straight to the nearest tree when
placed on the ground – even attempting to
climb up the team’s tripods.
Eventually, the researchers gained
around 40 minutes of footage from moreMoves like a marsupial,
climbs like a primate
than 200 videos, from which they
analysed 198 movements on the
ground, ascending and descending and
moving along a narrow horizontal beam.
They found that, unlike other mammals
such as cats and dogs that use two legs from
the same side to support each other, koalas
use a gait that allows greater stability
from diagonally opposite leg pairs when
climbing.
“As far as we can tell, they are the closest
thing we have to primates in Australia,” says
Clemente, “likely because of the similar
gripping structures on the hand. They do
this more so than other tree species like
possums, from which they share a common
ancestor.”
Unlike primates, though, their speed
was more consistent with their sleepy
demeanour, only reaching 2.5 kilometres per
hour – although they were surprisingly agile.
“We occasionally saw leaps of over one
metre from branch to branch, or a koala
moving along a branch while hanging
underneath just using their forelimbs,” says
Clemente.
On the ground their movements
were more like marsupials, walking then
bounding like rabbits. They achieved speeds
of up to 10 kilometres per hour – relatively
slow for their body mass, but possibly slower
than speeds they are capable of, the authors
suggest. –NATALIE PARLETTABIOLOGY
BIOLOGY
That sounds a bit fishy
‘Acoustic enhancement’ may help
with reef restoration.Young fish can be attracted to degraded
coral reefs by the sounds of healthy reefs,
new research suggests.
Australian and British scientists placed
loudspeakers on patches of dead coral on
the Great Barrier Reef and found “acoustic
enrichment” doubled the number of fish in
an area compared with patches where no
sound was played. And the fish stayed.This “could help to kick-start natural
recovery processes”, says Tim Gordon
from the University of Exeter, UK, lead
author of a paper in the journal Nature
Communications.
Colleague Steve Simpson says healthy
reefs are remarkably noisy. “[T]he crackle
of snapping shrimp and the whoops and
grunts of fish combine to form a dazzling
biological soundscape. Juvenile fish home
in on these sounds when they’re looking for
UNIVERSITY OF EXETER / GETTY IMAGES a place to settle.” – AMELIA NICHELE
Issue 86 COSMOS – 11