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Saving Australia’s favourite marsupial, one tree at a time

May 22, 2014
For the last six years Dr Matthew Crowther, research leader and Senior Lecturer in Biological Sciences in at the University of Sydney, has lead a groundbreaking study into a population of koalas in and around the NSW town of Gunnedah. We talk to him about what he’s discovered, and how it will help Australia’s favourite marsupial. 
You’re an expert in Australia’s favourite animal, the koala. How did that happen?

I grew up near bushland, and just used to spend a lot of time bushwalking, playing in the scrub and seeing lots of different native animals. Kids were allowed to do that back then.

I was pretty much on my own though, and it wasn’t until I went to uni that I met a lot of people who are also into marsupials.

For my PhD I researched a tiny little marsupial call the Antechinus, it lives up and down the east coast of Australia. We were trapping them to understand more about their habitat and looking for how many different species there were. It wasn’t until later that I began to focus on the koala.

That’s not very different from the research you’ve been involved in over the last couple of years with koalas?

Yes, that’s right, most of our research has been in and around Gunnedah and the Liverpool plains. The area was identified as a koala hot spot in a national survey in 2008. We worked on seven farms in the area, catching and tagging koalas with GPS tags so we could see how they spending their time, what they were eating and so on.
In the end we tracked fifty koalas to capture their movements, and we also got a vet to look over them when we first tagged them, so we could get some data on diseases in the population.

One of the main reasons we’re doing the research in this area is because back in the 1990s there was a lot of native tree planting, and we wanted to find out if it’s these new trees that the koalas are eating.

And is it those trees?

It’s actually very tricky to pin down. Koalas are quite fussy, not only do they like certain types of trees, they like a certain mixture of trees grown on certain soil types. We think it has something to do with the concentration of nutrients in the soil. Different trees produce different types of toxins, and the concentration of these toxins will vary depending on the soil type.

So koalas like to eat species like the River Red Gums, White Box, Yellow Box and Bimble Box– but they also need shelter trees to hang around in during the day.

Shelter trees are extremely important because during the summer they will just die of heat stroke if they can’t get out of the sun. Until we did the research we didn’t realise how important they were, but koalas will literally die of heat exhaustion on a hot day if they can’t get out of the sun.  But these are usually Kurrrajong or Casuarina trees. The eucalypts aren’t very good at keeping off the sun.

How is it that they can cope with a diet which would poison most animals?

It’s really fascinating that they’ve evolved to eat like this, and it’s largely because of the bacteria they have in their bowels.

/><br /> <br /> <strong>Is it true that koalas get drunk on the toxins from the leaves?</strong><br /> <br /> No, I’m afraid that’s a bit of an urban myth. But they do sleep for about 20 hours a day – so when we see them they often look a bit groggy. They need to conserve their energy for the night time when they’ll range quite a long distance sometimes, and climb three or four trees to feed.<br /> <br /> <strong>So what did you find out about the diseases in this population?</strong><br /> <br /> We found a range of diseases, including koala chlamydia, which is a shame because the koalas weren’t showing any outward signs of chlamydia. We thought the population was clear of the disease, but then a lot of the tests came back positive.<br /> <br /> Unfortunately we couldn’t do anything about it, to treat the chlamydia we’d need to keep the koalas in captivity for a couple of weeks and put them on antibiotics, and we can’t do that to the whole wild population.<br /> <br /> What we need is a way to test for the disease in the field, then we might be able to do something about it.<br /> <br /> <strong>So what can we do to protect our existing koala populations?</strong><br /> <br /> Really it’s all about habitat. It’s about protecting the habitat that’s already there, planting more trees, and the right combination of trees on the right soils.<br /> <br /> At the moment a lot of the tree planting goes on beside the road, and that causes problems too because the koalas get hit by cars. What we really need are tree corridors on fertile land where the trees will grow nutritious leaves that the koalas can eat.<br /> <br /> And it’s about climate change, the heat waves around Gunnedah are getting worse, last year the temperature got up to 48 degrees on one day, and we just find koalas dead at the base of the trees. Some of the local farmers even put out water for them when it gets hot because they need to drink.<br /> <br /> They need a good mix of food trees and shelter trees, and the population to stay strong enough to give us time to find a cure for the diseases like chlamydia.<br /> <br /> <em>Want to know more about how technology is helping to diagnose koala chlamydia? Check out this <a href=video.