News

Study provides clues for koala conservation



13 April 2011

Dr Mathew Crowther is studying the koalas in Gunnedah, which hosts one of the only thriving populations in NSW, to learn more about these shy mammals in the hope of conserving koalas across the state. Photo credit: D.Lunney
Dr Mathew Crowther is studying the koalas in Gunnedah, which hosts one of the only thriving populations in NSW, to learn more about these shy mammals in the hope of conserving koalas across the state. Photo credit: D.Lunney

After trapping koalas, the researchers attach GPS collars to track individuals for weeks to months. Photo credit: D.Lunney
After trapping koalas, the researchers attach GPS collars to track individuals for weeks to months. Photo credit: D.Lunney

In a study that hopes to boost conservation of Australia's most iconic animal, University of Sydney researchers have gained a rare insight into the habits of koalas and discovered that the vulnerable mammals are most at risk from living in small patches of bush near roads and train tracks.

Led by Dr Mathew Crowther and colleagues, the research will be featured on ABC TV's Catalyst program on Thursday, April 14.

The study, conducted in the town of Gunnedah that has one of the only growing koala populations in the state, has shown that while koalas are suffering from being restricted to isolated patches of trees, simple tree planting may be the solution to expanding their habitat and allowing their populations to grow.

Dr Crowther says the research highlights the challenges of habitat loss and fragmentation faced by koalas in NSW and identifies high-risk areas that must be managed to reduce koala mortality.

"It is encouraging to see that koalas can use a variety of trees, including newly planted eucalypts, and are not restricted to old growth forests," he said.

"Unfortunately, this also means that koalas will use trees planted next to roads, train tracks and fence lines, and we saw very high rates of koala mortality in these areas. We also saw signs that the small patches of trees available to koalas could not support them during tough times, such as droughts, when resources are scarce."

It has been known for the last 20 years that koala numbers across Australia are dwindling due to a combination of deforestation, habitat fragmentation and disease. In 2006, prompted by concerns that koalas were in serious decline in NSW, the state government commissioned a survey to establish koala abundance and distribution in NSW.

The survey, created by Dr Crowther and colleagues from the Department of Environment, Climate Chance and Water (now the Office of Environment and Heritage), was sent to a random sample of residents throughout NSW and revealed that koala populations across the state are dropping, with lower numbers on the south coast and higher abundances in the north coast. The survey also identified rare pockets - such as the town of Gunnedah - where populations are both high and increasing rapidly.

"We were interested in studying the koalas in Gunnedah because we wanted to work out why the population was increasing in this particular place," said Dr Crowther, who used results of the survey to create a map of the distribution and abundance of koalas in NSW.

"We knew a massive tree planting effort had taken place in the 1990s, so we wanted to know if that campaign had led to an increase in koalas and whether we could use this information to guide areas of koala decline."

In order to study the Gunnedah population, in particular to find out where they move and what trees they use, the researchers trapped koalas and attached Global Positioning System (GPS) collars, which provided data on each individual's location over an average period of three months.

Results showed that koalas were actively using the newly planted trees in Gunnedah, which are likely to be the reason for the koala's increase in the town. They prefer to use a variety of trees throughout the night, including some old growth trees, and are limited to a small range of movement, generally less than 2 km, mostly within small patches of trees.

Dr Crowther says the fact that koalas have such limited habitat is worrying for their survival, but there is hope that reforestation can benefit them.

"We saw lots of koalas die during high summer because they couldn't find enough food and water within these small patches," he says.

"The koalas would benefit from having access to multiple patches of trees so they have a few more options and don't have to compete with each other during hard times, especially with the extreme weather events predicted under climate change. The fact that the koalas in Gunnedah are using trees planted in the 1990s means that simply planting the right types of trees could expand their habitat and mitigate some of the current problems we are seeing with koalas living in such fragmented patches of forest."

Contact: Carla Avolio

Phone: 02 9351 4543

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