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INTERVIEW: Re-establishing koala populations in unoccupied habitat

by Joanna Horsfall | AUGUST 17, 2018

In the face of declining koala populations in Queensland, one team of researchers from The University of Queensland is on a mission to breathe new life into a suitable yet currently unoccupied habitat in the Fraser Coast Region. Joanna Horsfall interviewed the Koala Ecology Group’s Senior Scientist Dr Sean FitzGibbon and Chief Veterinarian Dr Amber Gillett about their triumphs and challenges in re-establishing a wild koala population.

 

J: Your current project is called A new approach to conserving Queensland’s koalas: re-establishing koala populations in suitable, unoccupied landscapes within the species’ range.’ What makes your approach unique?

S: We are very excited about the Tandora project. It is a new approach for koala conservation in Queensland because we’ve been able move to koalas back into an area where they used to occur, but haven’t been seen for about one hundred years. The last koala on the privately-owned property was shot for its pelt in the 1920’s and the current owners were very supportive of re-establishing a koala population.

The project began when numerous koalas from elsewhere in the Maryborough region were displaced by a new urban development. These koalas were taken to Australia Zoo Wildlife Hospital for treatment (most were infected with chlamydia or had been orphaned). We obtained permission to relocate these koalas to Tandora when they had finished their treatment at AZWH. Tandora (>4000ha) was only 20km from their previous home ranges but it is largely isolated by surrounding rivers and agricultural land. It contains the same species of food trees and large areas of high-quality habitat as the nearby koala-occupied bushland.

We have been monitoring the population since the first relocations occurred in February 2014. Since that time eight young have been weaned at the site by the founder koalas. We are currently examining the genetics of the entire population to see if there is sufficient diversity and if it would benefit from supplementation of additional suitable individuals.

 

J: What measures did you take to initially manage the population?

S: Our aim was to establish a population of healthy koalas in high-quality habitat. The first step we took was to ensure all the koalas were free of chlamydial infection and in good health. We fitted them with ear tags and tracking collars and then released them into an area with a high density of food trees. For several of the koalas, we used a soft-release approach to help settle them into their new environment. We installed temporary fencing to constrain each released koala to a group of about four or five large food trees. After approximately seven days we opened up the fencing so the koala could move freely throughout the landscape.

We’ve been using proximity-logging collars to see when the koalas are interacting with each other and who they have been interacting with. The collars each emit a RFID signal and also contain a reader, which will log an interaction if two animals come within close proximity to each other. From these data, we are able to figure out which individuals may have contributed genetically to the second generation. The veterinarian (Amber) also gives the koalas a very thorough health check in the field every three-to-four months with her mobile lab. She gives them an ultrasound, looking for pregnancy or any evidence of reproductive disease, takes eye and urogenital swab samples for chlamydia testing (through a specialised laboratory), as well as blood, bone marrow and other samples important for assessing the clinical health of each individual.

 

J: What have your disease tests revealed so far?

S & A: The great news is that the population has remained free of chlamydial infection and disease. Interestingly, because the koala population is currently isolated, it has served as an unintended experiment to look at how successful and long-lasting chlamydial treatment (specifically antibiotic treatment) is in wild koalas living in their natural environment. Most of the koalas had chlamydia when they came into the Australia Zoo Wildlife Hospital, and were treated with antibiotics. Normally, treated koalas are put back into the wild where they came from, and where we have no control over the level of disease in the broader population. Therefore, if they develop chlamydial infections again you couldn’t be sure whether it was because the koala has been reinfected by interacting with another infected individual, or because the chlamydia has lingered in the koala’s body  and flared up again. This site is unique because we know there are no other koalas, so there is no potential immigration of chlamydia into the population (i.e. no risk of them interacting with another diseased koala). So far, we haven’t had any koalas with chlamydial infections again since release (some for up to 4 years), so it certainly looks like the antibiotic treatment does provide significant long-term benefit where there is no risk of reinfection.

 

J: Can translocation be considered a proactive, rather than reactive, conservation strategy for threatened species like the koala?

S: Many people have a negative view of koala translocation because they only see it in terms of facilitating habitat clearance for development. But in many other species, translocation has proven a vital conservation strategy. I think we need to start thinking about potential koala translocations in this broader context, as a way of re-establishing populations in suitable areas where they have become locally extinct. I certainly am not advocating translocation to facilitate development, but as our study at Tandora has shown, it can be a really useful strategy to increase the distribution of koalas within their natural historical range, rather than only trying to conserve them where they currently remain. We can take them back to where they used to occur but haven’t been for a long time, so long as the reason for their disappearance is no longer continuing at that site anymore. For example, I know from our fieldwork in central Queensland that there are large areas of regrowth eucalypt forest that could support koalas. If we can just help to re-establish them in certain areas, it might be enough to get them going and become self-sufficient quite quickly. Koalas are pretty good at finding each other and breeding. And you don’t necessarily have to source animals in the same way that we have in this project. For example, they could be bred in captivity from suitable source animals, specifically for that purpose.

 

J: How might your approach to differ if captive-bred koalas, rather than wild koalas, were relocated?

A: It would be very important to take a hands-off approach with captive-bred koalas if they are to be released. Koalas can quickly become accustomed to human presence and the benefits that may come with that (such as fresh leaf being placed in their enclosures). Captive-bred koalas would need to experience realistic habitat features such as mature tree heights, different bark types that come with differing tree species and tree age, and varying weather conditions and wind strengths that, if they aren’t otherwise exposed to, they might struggle with when introduced into a natural environment. Another important consideration would be access to multiple different leaf species and leaf at varying stages of maturation. There is mounting evidence to suggest that a koala’s hindgut flora is quite specific and tailored to the species of eucalypt leaf that they commonly eat in their geographical region. As such, consideration may need to be given to providing leaf from the recipient site to allow the koalas’ gut flora to suitably adapt to processing leaf from the area before release.

 

J: What lessons have you learnt from monitoring the koalas that might inform similar projects in the future?

S: To prevent koalas from wandering away from the new site, we’ve talked about measures like collecting their own scats and using them to mark their scent at the environment before the koalas are released.

A: And even scent-marking the trees, too – like marking trees with the odour of a male’s scent gland such that it appears there is already some koala activity in the area. That may play a part in settling koalas into a particular area. There is still a lot to learn about how important that dynamic really is.