Koalas hug trees to keep cool, say scientists
Trees act like thermal heat sinks to help the marsupials cope with the extreme heatwaves caused by climate change, say scientists
Koalas spotted clinging to tree trunks or sprawled across branches aren’t just hanging out, say scientists, they’re keeping cool.
A new study published in the journal Biology Letters used thermal cameras to show that during heatwaves in Australia, the koalas used the surprisingly cold surfaces of trees like an icepack.
“They’re just stuck out on the tree all the time so when hot weather comes they’re completely exposed to it,” Dr Michael Kearney of the University of Melbourne told the Guardian Australia.
“The fur on their tummy is quite a lot thinner than the fur on their backs, so they’re pushing that fur and that part of their body as much against the tree as possible.
"Any way that they can lose heat that doesn’t involve losing water is going to be a huge advantage to them. Dumping heat into the tree is one of those methods.”
Animals and birds avoid overheating in hot weather through this ‘evaporative cooling’ process, but while koalas can pant and lick their fur like dogs to produce a similar effect, these methods are ‘emergency only’ for a creature that can’t easily refill on water.
Koalas don't have sweat glands and so have to find other ways to stay cool through evaporation.
The researchers noticed that in the winter koalas stay higher up in the trees, nearer to the leaves, but in hotter weather they move further down - behaviour that seems unusual but makes perfect sense if they are using the tree trunks as heat sinks.
It’s thought that the trees stay cool because of their strong thermal inertia (meaning they heat up and cool down more slowly than their surroundings) and by pulling up cool groundwater into their trunks.
The team measured the temperature of four species of eucalyptus and one type of acacia and found that on days as hot as 39C the trees could be as much as 7 or 8 degrees cooler. When they used thermal cameras to check their theories they saw it was “obvious” what the animals were doing.
“You could see the koala sitting on the coolest part of the tree trunk with its bottom wedged right into the coolest spot,” Dr Kearney, a co-author on the paper, told the BBC.
The studies were conducted as part of a larger research project into the effects of climate change on land-dwelling animals in Australia.
The researchers predict that this tree-hugging behaviour will become increasingly common as the continent experiences longer and hotter heatwaves – but that once temperatures go past 40 degrees even this might not be enough to help koalas cool down.
- 1 Saudi Arabia mosque bombing: Two volunteer security guards hailed as heroes for stopping Isis suicide bomber reaching worshippers
- 2 Maisie Williams has an excellent message for one confused fan
- 3 There is something wrong but very right about this Bible illustration
- 4 Puerto Rico, island of lost dreams: People are leaving the debt-hit territory in droves as near neighbour Cuba's star rises
- 5 Tampon tax scrapped in Canada after petition convinces conservative government
Saudi Arabia mosque bombing: Two volunteer security guards hailed as heroes for stopping Isis suicide bomber reaching worshippers
Maisie Williams has an excellent message for one confused fan
Archaeologists discover 2,400-year-old gold bongs in Russia
Tampon tax scrapped in Canada after petition convinces conservative government
Migrants in Kos: Photos show real tragedy after British tourists complain of 'awkward' holidays
EU referendum: David Cameron's rules are a 'democratic disgrace', says French-born Scottish politician set to be denied a vote
British tourists complain that impoverished boat migrants are making holidays 'awkward' in Kos
A nation of inequality: How the UK is failing to feed its most vulnerable people
Migrants in Kos: Photos show real tragedy after Brits abroad complain of 'awkward' holidays
Australian man punched in the face for defending Muslim women from abuse on train
EU referendum: David Cameron to deny EU migrants and under-18s the chance to vote
£16500 - £18500 per annum: Recruitment Genius: One of the leading Mercedes-Ben...
£27500 - £35000 per annum: Recruitment Genius: This is an exciting opportunity...
£19500 - £23500 per annum: Recruitment Genius: Experienced B2B Telemarketer wa...
Negotiable: Recruitment Genius: This global company are looking for two Showro...