Magnetic Island North Queensland
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A young koala's beach adventure

July 29th 2009
Island koalas' secrets studied

Natalie Briscoe and Andrew Krockenberger It has often been claimed that Magnetic Island's koala's are the most northerly population to be found in Australia. According to experts, recently researching Magnetic's koalas, however, this is not true. But, when it comes to actually seeing a wild koala this far north, then it might as well be. This also applies for the researchers who are trying to find out, among other things, and with climate change in mind, just how our koalas deal with heat and our harsh, late dry season and why the population appears to remain fairly stable without the booms and busts commonly experienced elsewhere.

The JCU team is headed by Associate Professor Andrew Krockenberger from the School of Marine and Tropical Biology (Cairns) who ran a field camp last week with zoology students at the Picnic Bay Recreation Centre.

One PhD student from Melbourne University with a particular interest in koalas was Natalie Briscoe who has studied koalas on French Island. This is her first time on Magnetic and, with the group, was catching, weighing and measuring koalas around Magnetic's famous Forts walk, where Island koalas appear most frequently.

“I'm interested in what maintains the koala population at this level. On other islands you see them boom and bust,” said Natalie.

The whole question is a rather open one and the team is interested to hear opinions from locals – particularly longer term residents with any observations of koala's in larger numbers than normal in times past.

Natalie has also been measuring factors such as wind speed and temperature on koala behaviour.

The team caught and released six koalas during the study period and are hoping to begin to understand just how far each koala ranges, what their territories are and what their densities are like.

Andrew Krockenberger says that koalas have been found as far north on the mainland as Shiptons Flat near Cooktown but, “They are very hard to find this far north.”

He also believes that our koala's are significantly smaller than those found in southern states. “Males grow up to 15kgs in the south but we found one that was about four years old at 7.5kgs,” he said, adding, “It might grow a bit more.”

Something that will be looked at in terms of climate and, ultimately, how koalas can deal with climate change, is changes fur density and other proportions. “We are modelling how much heat they are gaining in the sun relating to how much food they need to eat and their energy budgets.” said Andrew.

Just why the Magnetic koala population has seemingly remained so stable over the years is important to the team as population booms and the great difficulties of relocation at places like Kangaroo Island have been a sad feature of koala management.

Andrew has a hunch that it is, in fact, Magnetic's long and harsh dry season that keeps the koala population here from exploding.

“Natalie is looking in general at how climate affects them in the late dry. She's doing modelling on changes in climate patterns to predict effects in terms of distribution. Water is particularly important,” say Andrew. Over-heated koalas deal with the higher temperature by panting and licking their arms which leads to water loss.

Andrew is something of a koalapaedia and is happy to tackle popular koala misconceptions. If you believe, for instance, that koalas gain all their moisture from gum leaves and don't drink, then think again. During the heat wave and devastating bush fires in Victoria this year koalas were being revived and drinking directly from water containers. Andrew believes they probably drink dew from leaves as well.

And while their preferred food is leaves from our steely-trunked blue gums (Eucalyptus tereticornis) and narrow-leafed iron bark (Eucalyptus creba), Andrew says that Koalas have been documented eating paperbarks and even radiata pines, “but not in huge proportions.”

Andrew thinks that our dry season is, “crunch time for the eco-system,”

“The harsh late dry may slow down youngsters and the newly weaned or females don't manage to raise babies,” says Andrew. But he acknowledges other factors such as diseases like chlamydia (known to be a problem for Island koalas) and even leukemia, which he is aware of from “very anecdotal” reports.


Magnetic Times found this koala crossing the West Point
track last week and noticed its arms, legs and underbelly
were wet. It had come from the mangroves!


Yet another factor - which relates to the Magnetic Island koalas not actually being native to Magnetic but introduced in the 1930s - is the “founder effect” by which the first koalas may have had a genetic condition which has affected reproduction rates. Predation from dogs is another factor as is that from large pythons as well as fires. Large pythons are however very rare on Magnetic and although Magnetic Times has reported occasional and viscious dog attacks on koalas it seems unlikely they are keeping a booming population at bay. As for fire, Andrew says, “My gut feeling is that if many koalas are getting burned people would know about it.”

It seems that koalas grow to different ages in different places. According to Andrew, Twenty years is pretty old in some populations while twelve is old in northern NSW. Nobody knows how long the Magnetic koalas live for and determining the age of the animals is difficult with living animals. Tooth wear is one, not very accurate method. The best age indicator is “growth rings” which can be found in the “cementum” around the roots of koalas' teeth. Not to be tried on living animals, Andrew is however particularly keen to check on dead koalas and is urging locals who come across road-killed koalas to pass on their location or take the bodies to the QPWS rangers' Office in Picnic Bay (Ph: 47785378).

It seems like the most important terrestrial animal to Magnetic Island's tourist appeal are more mysterious than we might think. But the work of Andrew and Natalie, which will see them returning periodically to Magnetic, may slowly help us understand and better look after our fluffy Island icons in a time when the need for knowledge to mitigate climate change and other threats has never been greater.

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Island koalas' secrets studied
 
3 comments
 
chasmac
July 29th 2009
I have always been fascinated by the story of the introduction of koalas to Magnetic Island. No shred of evidence has ever been provided for this story. Usually the Hayles family name is involved and the 1930s is mentioned. That's it.
Let's presume some koalas were introduced a long time ago. Can we establish for sure that there were no koalas before then? Where did these 'introduced' koalas come from? Townsville? Brisbane? Adelaide?
Is it possible to examine the DNA (or something) from the present population to see if they are similar to some other population somewhere else?
I know of a paper written about Magnetic Island's koalas and the impact of the 1972 wildfire (Heinsohn, G.E. (1973). The Magnetic Island bushfire – 1972) and I can recall a research group here about 20 years ago (possibly from UNSW or Macquarie) who collected blood samples from the Forts koalas - I never did see the work written up so I don't know what they found.
 
Linda
August 4th 2009
When the National Sparks and Wildfire Service set fire to the island about 10 years ago, saying they were planning to burn about 4%, then came the 60 knot winds, rapidly upping that to 11% and finally achieving 25%, bush walkers were reporting seeing barbecued koalas still in the skeletons of trees.
 
Nicholas
January 18th 2011
In relation to the above story. Tagging and releasing 6 koalas is a joke. I was with the Macquarie University, school of Biological sciences team that came to the Island in 1998 and caught, tagged, DNA sampled and released over 54, although catching a total of 89 Koala from across the entire Island.

They have been tagged with trovan micro chips in the back on the neck. The records state time/ date caught ,weight measurements and health of animal including sex. And anyone who knows about Koalas knows that they do not get as big as our southern counterparts because we do not have the cold weather as they do in the south of our country and most importantly we do not have large trees to climb to get to their food source "OMG " , example. gum trees in Victoria are 3 times the size of our Island trees. Just picture a massive blue gum compared to the ironbark you see on the island. OMG

This is also several other varieties of Ironbark on the Island including broad leaf, silver leaf and fake ironbark which contains no euco for the Koalas. As well as another euco on the Curlew flats I cannot recall the name of. And as for Blue gums, there is only two places on the Island that have blue gums and that is at the Bowermans property on the way to west point and the western side of the horseshoe Bay lagoon area, to say it's a favorite is entirely inaccurate as only 20% of the Koalas live and travel in those areas. No bluegums at the forts, Arcadia, Nelly bay , cockle bay hill or the Golf club.
It is a favorite to those that have eaten it regulary which on the Island is a very small few. Several locals have planted gums to encourage Koalas into their properties.
If you have never eaten fish how can fish be you favorite food.
They will also lick dirt and dust to clean out their system and will drink water if dehydrated enough. Our Islands Koalas have been in steady decline for the last 20 years due to desease,fires, dogs and human activity

Anyone wanting this report or information should contact the Island QPWS office and ask for information from the study done by Mrs Valma Joan Neville from the Macquarie university . It should be located in the Koala file in the Wildlife section, as I put it there 13 years ago.
It contains chip numbers of all 54 Koalas and is a comparison of koala on Magnetic Island and Kangaroo Island,
If Rangers cannot find please ask Ranger Nathan Winn to contact N.Mulcahy and they can obtain copies.
I was given personal copies as I was involved in the process as a member of the Island community. who just happened to study Koala habitats on the Island and where colonies are located.
thank you

For the University people you may wish to cantact a Proffesor Summers at Vet science JCU as I took him several koala for necropsy and other about 10 years ago, trying to identify what deseases where killing our koalas as well as other information that comes from a detailed necropsy, he also had chooks from the Island as well, from Anne Roches place at the base of Gifford street. I believe he was doing the same tests on them.

If the Uni people used chip scanners on the Koalas they caught and released we might have received some great information about our local Koalas but not utilising previous studies has wasted this opportunity. A dissapointment but maybe in the future this can be done. Thank you


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