Recovering the mainland Eastern Barred Bandicoot.
Many species are being driven to extinction by anthropogenic activities that have resulted in habitat loss and alteration, species introductions, pollution and climate change (Mace et al. 2008). In Australia, Red Foxes Vulpes vulpes and Cats Felis catus pose a major and intractable threat to populations of native wildlife (Dexter and Murray 2009; Coates 2013; Sharp et al. 2014). To improve the conservation status of threatened species, the threatening process leading to their extirpation must be removed or considerably reduced, (Short 2009, Morris et al. 2015). This can be achieved in situ by managing protected areas, or via translocations (Seddon et al. 2014). Factors that can improve the success of translocations include appropriate founder numbers, greater genetic diversity of founders, source of founder population, suitable habitat and size of the release area (Fischer and Lindenmayer 2000; Short 2009; Morris et al. 2015).
The Eastern Barred Bandicoot Perameles gunnii (mainland form, un-named subspecies) is a Critical Weight Range species (Johnson and Isaac 2009) weighing <1 kg. It was formerly found across the basalt plains of south-western Victoria, inhabiting grassy woodlands and feeding on a variety of invertebrates and plant matter (Seebeck 1979; Dufty 1991). The introduction of the Red Fox and extensive habitat alteration and destruction that occurred with European settlement resulted in >99% habitat loss, widespread population decline (Backhouse et al. 1994) and a subspecies that is now listed as extinct in the wild (Advisory List of Threatened Vertebrate Fauna in Victoria 2013).
In 1989 the Eastern Barred Bandicoot Recovery Team was formed in response to a sustained decline of the last remaining mainland wild population in Hamilton, Victoria. The first action of the recovery team was to translocate wild bandicoots from Hamilton to reintroduction sites, where foxes could be managed or excluded. Winnard and Coulson (2008) reviewed the eight mainland reintroduction sites; each had varying degrees of fox presence and bandicoot population establishment success. All reintroduction sites that could not be kept free of foxes ultimately failed (Winnard and Coulson 2008).
The Eastern Barred Bandicoot has several traits that make it ideal for successful recovery. Gestation is just 12.5 days, young are weaned at 55 days and are capable of breeding from 3 months with breeding possible throughout the year (Backhouse et al. 1994). They are able to exploit modified habitats such as the Hamilton refuse tip, agricultural areas in Tasmania and areas severely overgrazed by macropods (Backhouse et al. 1994, Driessen et al. 1996, Winnard et al. 2013). Their primary habitat requirement is that release areas are fox-free.
Current Eastern BarredBandicoot populations
The only way to establish viable populations of Eastern Barred Bandicoots within their historic range is to exclude foxes by surrounding reintroduction sites with predator-barrier fences. There are currently three reintroduction sites surrounded by these fences: Mount Rothwell Biodiversity Interpretation Centre, Woodlands Historic Park and Hamilton Community Parklands. Mount Rothwell, near Little River, is a 420-ha privately owned reserve and the only site that has remained fox-free since bandicoots were released there in 2004. It is also the only site that has never experienced a bandicoot population extinction and currently holds the largest population of mainland Eastern Barred Bandicoots, at around 600 individuals (unpubl. data). Woodlands Historic Park, 20 km north of Melbourne, was the first Eastern Barred Bandicoot reintroduction site in 1989, but issues with kangaroo management and a fence that did not effectively exclude foxes resulted in the decline of this population to extinction (Winnard and Coulson 2008). In 2010, Conservation Volunteers Australia partnered with Parks Victoria in managing this site, upgrading the fence and removing all foxes. After three continuous months of no fox sign within this 235 ha reserve, 47 bandicoots were released in 2013. This population is now estimated at 340 individuals (unpubl. data). Hamilton Community Parklands in south-west Victoria is the smallest reintroduction site at 100 ha. This site also has a long history with Eastern Barred Bandicoots, with the first release occurring in 1989, but as at Woodlands Historic Park, this fence did not exclude all foxes and the population declined to undetectable levels in 2004 (Winnard and Coulson 2008). In 2007, after the fence was upgraded, Eastern Barred Bandicoots were re-released and the population did well until further fox incursions started in 2013. These foxes proved difficult to remove and had a catastrophic impact on the bandicoot population, which declined to less than 20 individuals (unpubl. data). Conservation Volunteers Australia has now partnered with the Department of Environment, Land, Water and Planning. Together they have restored the Hamilton fence and eradicated foxes from the reserve. In April 2016, 20 bandicoots were released into the reserve to boost genetic diversity and help return the Eastern Barred Bandicoot population to its former glory.
The captive breeding program at Zoos Victoria has been instrumental in preventing the extinction of this subspecies. Starting in 1991 at Healesville Sanctuary (Krake and Halley 1993) with 23 individuals, nine institutions have successfully bred Eastern Barred Bandicoots for release (in alphabetical order: Healesville Sanctuary, Kyabram Fauna Park, Melbourne Zoo, Monarto Fauna Complex, Serendip Sanctuary, Taronga Zoo, Taronga Western Plains Zoo and Werribee Open Range Zoo). A total of 888 bandicoots have been produced in captivity, with 551 released into eight reintroduction sites. Today the primary role of the captive breeding program is to hold an insurance population until the mainland Eastern Barred Bandicoot is secure in the wild, but offspring produced are still released as founders into new sites along with free ranging individuals from other reintroduction sites.
The Plan for Recovery
With only 800 ha of fox-free land and a long-term captive breeding program, the Eastern Barred Bandicoot recovery team has so far been able to prevent the extinction of this subspecies. However, to recover this subspecies and remove it from the Advisory List of Threatened Vertebrate Fauna in Victoria, more fox-free land needs to be secured. The Eastern Barred Bandicoot recovery team is embarking on an ambitious plan to increase population size to at least 2500 individuals, to prevent further loss in genetic diversity (Hill et al. 2010), using predator-barrier fences, islands and guardian dogs.
Predator-barrier fences are frequently used to protect endangered species from predation by introduced mammals (Moseby et al. 2011; Young et al. 2013; Norbury et al. 2014). There are differences in opinion over whether the high cost of constructing predator-barrier fences has significant conservation benefit (Scofield et al. 2011; Innes et al. 2012). In terms of the Eastern Barred Bandicoot, predator-barrier fences that exclude all foxes have so far been the only proven method to allow bandicoot populations to establish and persist for at least 10 years. For this reason, a new fenced reserve will be established. Tiverton Station, near Mortlake in western Victoria, will be Victoria's largest fenced reserve at around 1000 ha and capable of holding at least 1000 Eastern Barred Bandicoots. Fencing is due to be completed in 2017, followed by Red Fox, Cat and European Rabbit eradication ahead of a proposed bandicoot release in 2018. Construction of the fence is expected to cost around $700 000. This, combined with the cost of regular (ideally daily) fence checks and maintenance to ensure the reserve remains fox free, makes this an expensive conservation initiative. While predator-barrier fences are effective, their limited size and significant ongoing management costs make them unsuitable on their own for the long-term recovery of this subspecies. Therefore, Eastern Barred Bandicoot conservation needs to move beyond the fence.
Offshore islands, free from introduced predators, are increasingly being used as release sites for threatened species (Seddon et al. 2015). Although sometimes controversial, assisted colonisation to islands has been critical for preventing the extinction of some species, for example Rufous Hare Wallaby Lagorchestes hirsutus (Richards 2012), Gilbert's Potoroo Potorous gilbertii (Stead-Richardson et al. 2010), Kakapo Strigops habroptilus (Lloyd and Powlesland 1994) and Little Spotted Kiwi Apteryx owenii (Jolly and Colbourne 1991). In Victoria, French Island and Phillip Island appear to contain suitable habitat for Eastern Barred Bandicoots (unpubl. data) and are fox free, or in the case of Phillip Island, are near fox free (Rout et al. 2014). These islands offer an alternative solution to fences but as they occur outside of the Eastern Barred Bandicoot historic distribution there is some uncertainty around the ability of bandicoots to establish and maintain populations on them. A trial release of 18 non-breeding bandicoots on French Island occurred in 2012 (Groenewegen 2014). This trial found that the habitat on French Island was suitable for Eastern Barred Bandicoots but highlighted an issue with feral Cats that would need to be addressed prior to any further releases (Groenewegen 2014). A trial release of breeding Eastern Barred Bandicoots on fox and cat free Churchill Island, a 57 ha island off Phillip Island, is currently underway. These bandicoots will be monitored for 2 years to determine how they use the habitat and how they might influence island flora and fauna. This will allow a more informed decision on the suitability of Eastern Barred Bandicoots for release onto French and Phillip Islands. As both of these islands are inhabited, community engagement and involvement in the decision making process is a critical part of these island projects.
For centuries livestock guardian dogs have been used to protect domestic animals from predation in Europe and Asia (van Bommel and Johnson 2012). They do this by forming strong bonds with the animals they guard and fiercely protect them from predators by confrontation, actively maintaining a territory and deterring predators from entering and using that area (van Bommel and Johnson 2014). In 2006 Maremma guardian dogs were deployed on Middle Island near Warrnambool, Victoria to protect Little Penguins Eudyptula minor from Red Fox predation (Bourchier 2015). This has resulted in a steady increase in colony size and breeding success (Bourchier 2015). Following the success of this project, a novel trial is planned to test whether Maremmas can sufficiently reduce fox and cat densities or alter their behaviour to allow the establishment of Eastern Barred Bandicoot populations. As bandicoots are small and nocturnal they would be difficult for Maremmas to bond with, therefore around 10 sheep will be deployed at trial locations for the dogs to bond to. There are three trial sites proposed; Tiverton Station, Mooramong and a third yet to be determined site. At each site, 50 ha will be fenced to contain bandicoots, dogs and sheep, but access by foxes and cats will be permitted. Foxes and cats in the area will be radio-collared before and during deploying guardian dog deployment to test whether they alter their behaviour in response to dog presence. If there is active avoidance of the area by introduced predators, approvals will be sought from the Victorian Translocation Evaluation Panel to release bandicoots into the site to test whether they can establish a population. If bandicoot populations can become established in these areas, it may not always be necessary to confine Eastern Barred Bandicoots behind predator-barrier fences or on islands. This would make significantly more land available on mainland Australia where Eastern Barred Bandicoots could flourish. The technique could potentially have wider applications in conserving many other Critical Weight Range species that are threatened with extinction by fox and cat predation.
The Eastern Barred Bandicoot recovery team is embarking on ambitious plans to recover this subspecies from near extinction. Some projects may be unsuccessful, but if just two succeed, we should see the return of wild, free ranging populations in Victoria and stand a good chance of removing the Mainland Eastern Barred Bandicoot from the threatened species list.
The Eastern Barred Bandicoot Recovery Team is a multi-agency team with representatives from (in alphabetical order) Conservation Volunteers Australia, Department of Environment, Land, Water and Planning, Mt Rothwell Biodiversity Interpretation Centre, National Trust of Australia, Parks Victoria, Phillip Island Nature Parks, The University of Melbourne, Tiverton Property Partners and Zoos Victoria. The University of Tasmania, state and federal government and private donors are also essential contributors to Eastern Barred Bandicoot recovery and the above mentioned projects. Thank you also to Graeme Coulson, Richard Hill, Michael Magrath, Marissa Parrott, Duncan Sutherland and an anonymous reviewer who commented on an earlier draft of this article.
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Received 10 September 2015; accepted 5 May 2016
Zoos Victoria, Wildlife Conservation & Science, PO Box 74, Parkville Victoria 3052, Australia.
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|Publication:||The Victorian Naturalist|
|Date:||Jun 1, 2016|
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