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‘We discovered that they were in fact cooling themselves on the trunk’

Natalie Briscoe’sresearch into koalas discovered that the marsupials hug trees to keep themselves cool, providing valuable insight into how they adapt to their environment.

 

‘The overall aim of my PhD was to study the impact of climate change on koalas and observe how they use their environment to cope. 

During my honours year I studied climate change impact prediction on a common butterfly species and I wanted to do something similar for my PhD. 

I took the same approach to both animals, looking at their physiology, morphology and behaviour throughout many sub-projects. This approach is very useful for seeing how climate limits species now but it is also a reliable way of predicting how climate change will affect animals in the future. 

Butterflies and koalas are both very well studied, but koalas are particularly interesting with regard to climate change because they live over such a broad range of environments. 

They are found from the tropics in Queensland, to semi-arid areas in Central Australia, right down to temperate Victoria. 

‘I find it amazing that they can cope across this range of climates and I wanted to explore how their traits influence their coping methods.’

I find it amazing that they can cope across this range of climates and I wanted to explore how their traits influence their coping methods.

Looking at variation in physical features is really important for predicting the impact of climate change, but so are behavioural studies.

In Queensland and Victoria our fieldwork had us looking at how koalas use their surroundings. We began noticing odd behaviour, particularly how they sat hugging the trunks at the base of acacia trees, a plant they don’t eat. 

Many would assume, and previous study would indicate that they sat there simply for shade, yet we discovered that they were in fact cooling themselves on the trunk. 

Many have considered that animals cool themselves down by lying on cold ground or other surfaces, yet no one ever considered tree trunks could also be exploited in this way. I was very proud to get some media attention for this observation. 

‘Many have considered that animals cool themselves down by lying on cold ground or other surfaces, yet no one ever considered tree trunks could also be exploited in this way.’

Koalas do vary between climates: for example, koalas in Queensland are the smallest, and the fur length of koalas in Victoria is more than double the fur length of their northern neighbours. 

Using this traits-based approach, I could test how much energy koalas require to regulate their body temperature, and how much water they need in summer. 

We can use all the data we collected on koalas and the climates in which they live to see if it predicts where we should find them now. Even without using information about where forests are, these models can successfully predict where koalas will live, which suggests climate plays an extremely strong role in limiting their distribution. 

Now that we know this model is successful on koalas, we can start asking more questions and applying it to different species. Predicting the impact on systems is hard.

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There’s a lot of interaction between systems, but in a lot of species we’re already seeing shifts in what they’re doing, which match with previous predictions. The fact that we’re seeing a lot of responses in natural systems is an indication that the climate will change. 

We’re now thinking about the importance of adopting a more detailed approach so we can learn which species are likely to be the most vulnerable. 

Australia is a little different to the rest of the world. Rainfall is more important here than anywhere else. What’s coming out of many studies at the moment is that Australian species are likely to shift towards the coast. 

We are predicting more extreme heatwaves and therefore less rainfall, so as the arid areas expand, animals are likely to move to cooler, wetter areas by the coast, which is a problem because that’s where we live. 

That conflict between where animals are likely to shift to and where there’s actually available habitat for them is a difficult issue and something that interests me greatly. 

Specialising in the impact of climate change on animals is a good way for scientists to work out in the field, use their theoretical knowledge, as well as applying computer modelling. I’ve always had a love of animals and an interest in nature, but I am curious and I’ve always liked the theoretical side of zoology.

Specialising in climate change is a perfect combination of my passions.’

Natalie Briscoe’s  thesis is titled: “Understanding how climate affects the koala, Phascolarctos cinereus, the roles of behaviour, morphology and physiology”.

My PhD is an irregular series in which The Citizen speaks with recent Melbourne University PhD graduates. 

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THE CITIZEN is a publication of the Centre for Advancing Journalism. It has several aims. Foremost, it is a teaching tool that showcases the work of the students in the University of Melbourne’s Master of Journalism and Master of International Journalism programs, giving them real-world experience in working for publication and to deadline. Find out more →

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