By Mike Sullivan
Adapted from information and transcripts supplied by Western Australia’s Department of Biodiversity, Conservation and Attractions (DBCA), DBCA’s public magazine Landscope, WWF-Australia and Wildlife Queensland.
ONE OF Western Australia’s great conservation success stories – relocating healthy and abundant black-flanked rock-wallabies from one region to another, where their numbers had dwindled to the point of being untenable – has opened a heart-warming and educative third chapter.
A few months ago, 44 endangered black-flanked rock-wallabies (Petrogale lateralis lateralis) were carefully captured, loaded and flown by private charter aircraft from a Wheatbelt nature reserve in WA to a spectacular new home at Kalbarri National Park. That is, a ‘new home’ that had been cleared of invasive and dangerous species – a new home that was discovered to have been a favourite ‘old home’ for black-flanked rock-wallabies for thousands of years.
The work of WA’s Department of Biodiversity, Conservation and Attractions (DBCA) and World Wildlife Fund (WWF) is an emotional story that Australia wildlife enthusiasts are coming to regard as establishing new benchmarks in how to avert the loss of a treasured species.
This was more than a ‘simple’ rescue mission – it also set clear conservation planning, funding, local community engagement, cultural and scientific parameters for success. Long-term success. Repeatable success. And, hopefully, success adopted and adapted by other regions of Australia, perhaps for species that have come to similar conservation inflection points.
The black-flanked, or black-footed, rock-wallaby is a small and extremely agile species of wallaby that darts among rocky outcrops and caves, making it challenging to find and track.
DBCA’s Parks and Wildlife Service rangers’ recent success in moving 44 rock-wallabies from the Nangeen Hill Nature Reserve in the Wheatbelt to Kalbarri National Park is expected to further bolster the Kalbarri wallaby population. This was a population once thought extinct until feral animal control, through DBCA’s Western Shield program, and translocations enabled wallabies to flourish in Kalbarri once more.
In 2015, a tiny population of black-flanked rock-wallabies was rediscovered in the park by rock climbers, after being thought to be locally extinct for 20 years.
To boost conservation of the species, 72 rock-wallabies were released into the park, from larger healthy populations, between 2016 and 2017. The released animals were initially monitored using radio collars to understand their movements. The collars were later removed and the population has since been monitored using remote cameras.
Nanda Aboriginal Rangers assisted with this translocation and the flight was made possible thanks to the support of WWF-Australia. The success of the Kalbarri rock wallaby program makes it one of WA’s great conservation success stories.
Rock-wallabies continue to be recorded at Kalbarri, including a recent sighting at the skywalk – a considerable distance from the original release sites. The resurgence in rock-wallaby numbers in the park, and the diverse range of wildlife in Kalbarri National Park, has been supported by DBCA’s Western Shield program.
Western Shield: protecting WA’s vulnerable native animals from feral predators
DCBA’s Western Shield program aims to protect native species – primarily small and medium-sized mammals and some ground-nesting birds and reptiles – that are vulnerable to predation by foxes and feral cats.
Foxes and feral cats have been identified as a key cause of the extinction and decline of dozens of native animal species across Australia. Suppression of fox and feral cat numbers is a crucial step in successfully reintroducing, recovering or maintaining native fauna populations in the wild.
Research shows that one of the most effective ways to ensure the survival of many native animals in the wild is to manage introduced predators, including foxes and feral cats. Without this work, the many native species protected by the Western Shield program could be lost forever or only found in small, fenced reserves.
Western Shield’s work has facilitated increases in the population size and distribution of native species, including the numbat, quokka, western brush wallaby and black-flanked rock-wallaby.
Kalbarri National Park, situated on the Midwest coast of Western Australia, is a significant conservation area home to threatened native species, including the chuditch, also known as the western quoll (Dasyurus geoffroii), the black-flanked rock wallaby and malleefowl (Leipoa ocellata). The chuditch population was reintroduced to the site through translocation in the early 2000s, while the rock-wallabies were first translocated in 2016.
Covering more than 194,000 hectares, the park surrounds the lower reaches of the Murchison River, which has cut a magnificent 80km gorge through the red and white banded sandstone.
This river is critical to wildlife in the area. To protect animal species like the chuditch and rock wallaby, DBCA is managing foxes and feral cats at this site.
www.dbca.wa.gov.au/westernshield
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Western Shield: meet the predators
The arrival of the European red fox (Vulpes vulpes) fox in WA’s south-west in the late 1920s coincided with a steep decline in the numbers of smaller native mammals in the southern part of the state.
Fox management led to the recovery of several threatened species in the 1990s in WA, however, the impact of feral cats (Felis catus) became more prominent as a result. To address this issue, efforts are being made to integrate feral cat management into existing fox management by DBCA.
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Scientific methodology: saving rock-wallabies … and more
A Kalbarri rock-wallaby on the move. Photo: Still image from video footage of the Kalbarri rock-wallabies‘ translocation. © Alex Gore, DBCA Media.
THE TRANSLOCATION of threatened animals seeks to reduce the risk of extinction or the loss of genetic diversity by establishing new populations. In Western Australia, translocations of animals have been undertaken for more than 30 years.
The translocation of black-flanked rock-wallabies (Petrogale lateralis lateralis) into Kalbarri National Park over a three-year period from 2016 to 2018 is an excellent example of how translocations are organized and the expertise and teamwork required to carry them out. But despite extensive planning, even the translocation had some unexpected twists.
While most species of rock-wallabies are not considered threatened or endangered, there are significant concerns for a few species whose populations are declining. WA has five species of rock-wallabies, but the most widespread, the black-flanked rock-wallaby, is further divided into two subspecies and two distinct genetic races. The genetic variation has come about because of the isolation of different populations over many thousands of years, leading to the development of distinctive localised populations.
The subspecies Petrogale lateralis lateralis has the widest distribution of all, extending from one island off the southern WA coast all the way to Cape Range near Exmouth and Barrow Island off the Pilbara coast.
However, across this vast range, the rock outcrops actually occupied by these rock-wallabies are few and far between. There is a reintroduced population in Cape Le Grand National Park and six small populations that occur in the Wheatbelt near Kellerberrin.
Before the ecosystems were invaded
At the time of the European settlement, there were many more rock-wallaby individuals and populations. They were recorded as being very numerous in the Avon Valley National Park and Paruna Sanctuary. Heading north from Perth, scattered populations have been recorded in Kalbarri and Cape Range national parks, and in some remote desert ranges along the eastern edge of the Pilbara.
A small population occurs on Barrow Island, and black-flanked rock-wallabies were driven to extinction by foxes on Depuch Island, near Whim Creek.
WA currently has more than 249 threatened fauna species, including 41 mammal species, so the task to improve the situation for all of these species is a challenge.
A 10-year recovery plan for rock wallabies in WA was prepared in 2013 and identified a number of recovery actions,
For the black-flanked rock-wallaby, one of the most significant actions to improve the conservation outlook was to carry out translocations to increase the overall size and number of the populations. Why? Because as populations shrink or become fragmented, a species becomes more vulnerable to threats such as predation and environmental catastrophes, and they typically lose genetic diversity, making them at greater risk of extinction.
Science kicks in for wallabies
Genetic work by Dr Mark Eldridge at the Australian Museum used little pieces of ear tissue collected from rock-wallabies captured during regular trapping for monitoring or research. This study indicated that during the past 30 years, the Wheatbelt population has been losing unique genetic material because numbers of rock-wallabies had fluctuated widely and some colonies had declined to just a few individuals.
The small size of the outcrops in this area, droughts and challenges associated with the control of foxes and feral cats that infiltrate from surrounding farmland, made the establishment of new populations of rock-wallabies a priority for action.
Translocations to large areas of former habitat would serve to increase the number of individual rock wallabies and to preserve the current genetic diversity.
Black-flanked rock-wallabies occur in widely separated areas and there are genetic differences between populations. The Wheatbelt population occurs on six outcrops surrounded by agricultural land and is under particular threat because of the small area of habitat and continuing invasion by foxes and feral cats, held back in part by the regular DBCA Western Shield baiting.
In addition, there is a lack of alternative habitat for dispersal when the Wheatbelt population is growing during good seasons. In the past, too many wallabies in dry times resulted in over-grazing of their habitat and the rise of unpalatable weeds. So the source of rock-wallabies for the translocation was clear.
But where should they be translocated?
A large area of suitable habitat was necessary, where threats to the species could be controlled. Kalbarri National Park proved idea: rock-wallabies once occupied the gorge and were last seen there in about 1985.
The Murchison River, which snakes through the park for about 80km, and its side gorges are fringed by vast areas of rocky habitat. The area receives winter rains, similar to the Wheatbelt.
Regular aerial baiting to control foxes and recently feral cats is undertaken in this area, and feral goat control has been in place since 2006, significantly reducing the once-abundant pest.
Additional funds were made available from the Australian Government’s National Landcare Program to undertake wider feral cat control using DBCA’s Eradicat bait and to monitor its effectiveness.
Then, researchers got a surprise
As the DBCA-organised team was putting the finishing touches on the translocation plan, a rock climber in Kalbarri National Park snapped a photo of some wallabies near a popular but remote climbing site and sent them to senior park manager, Mike Paxman.
He immediately recognised the wallabies as a pair of rock-wallabies. DBCA’s Landscope magazine featured a story in its Autumn 2016 issue titled Surprise! Rock-wallabies found in Kalbarri National Park.
This prompted a rethink of the translocation plan. Searches on foot by DBCA and World Wildlife Fund (WWF) staff and volunteers tried to establish if other rock-wallabies were still in the park. Large areas of habitat were surveyed to obtain sightings or to find the distinctively shaped rock-wallaby droppings.
In conjunction with this work, traps were carried into the site where the ‘Kalbarri pair’ resided, with the intention of capturing them to get genetic samples so their relationship to other populations could be determined.
Unfortunately, the Kalbarri pair did not enter the DBCA’s traps, despite their best efforts to lure the wallabies, using every bait they could think of – including ‘pink lady’ apples, a known favourite. So they resorted to the next best thing – “watching the wallabies closely and then racing out to collect any newly deposited droppings”.
Dr Eldridge at the Australian Museum, who gladly accepted them and determined that the Kalbarri animals were genetically distinctive from other populations. His results revealed that their closest affinities were to the Calvert Range rock-wallabies (about 900kn away in the Little Sandy Desert, east of Newman), then those in Cape Range National Park and finally to the Wheatbelt animals.
The discovery of the Kalbarri pair and a failure to find any further individuals, led to a modification in the translocation plan.
“We were concerned that if anything happened to these precious animals the unique Kalbarri genes would be lost for good. So it became a priority for us to expand the population and plans were made to translocate 20 rock-wallabies in May 2016 to establish a new population of mixed Wheatbelt (from two of the large outcrops) to ensure the greatest possible mix of DNA, with the intention to include some Cape Range animals later to further improve the genetic diversity,” it was reported in Landscope.
“In addition to the translocation, we undertook a ‘supplementation’ where three Wheatbelt females were released near the Kalbarri pair so the male could breed with hem and perpetuate the unique Kalbarri genes.”
A second translocation – this time of 25 rock-wallabies – occurred in May 2017, and then, in May 2018, 20 Wheatbelt rock-wallabies and five from Cape Range National Park were released in the park.
Teams of DBCA and WWF staff and volunteers worked through the night before the translocations to check the traps set up to collect the animals so that by early morning the rock-wallabies we ready to be flown to their new home. Each wallaby was placed in a black cloth bag, put in a ‘pet-pack’ and then carefully loaded onto the aircraft.
Tracking and monitoring is vital
Once in Kalbarri National Park, each rock-wallaby was fitted with a radio-collar so their fate could be monitored.
Each radio-collar transmits on a different frequency and is fitted with a ‘mortality’ feature which indicates when there has been no movement for several hours. So, if a rock-wallaby dies or the collar falls off, park rangers can recover it and determine the cause of death.
In the late afternoon, the rock-wallabies were gently carried into their new home by the enthusiastic team, which included the DBCA and WWF staff and Bush Ranger cadets from the Kalbarri District High School.
Monitoring the translocations is very important. Surveying is carried out at the source site to ensure that the population is not negatively impacted by having animals removed, and at the release site, to determine the success of the translocation.
Kalbarri National Park rangers regularly travel to high points in the park to listen for radio-collared wallabies. If any mortality signals are received, they locate the animal and/or collar. Evidence showed one rock-wallaby died in 2016 from a fall; one was killed by a fox in 2017; and in 2018 two were killed by predators and two others apparently died after falls. Male rock-wallabies frequently wandered from the release area and a small aircraft fitted with radio-tracking aerials was used to locate them.
After the 2018 release, follow-up trapping at previous release sites was carried out to collect genetic samples. This resulted in several exciting results.
Genetic analysis by DBCA’s fauna geneticists, Kym Ottewell and university researcher Kristen Nilsson found that a translocated Wheatbelt female had a pouch young that possessed unique Kalbarri genes, but not those of the male of the ‘Kalbarri pair’. This indicated that other Kalbarri rock-wallabies were still in the area, albeit at very low density.
Kalbarri genes were also present in a juvenile male captured where the supplementation was undertaken, meaning the male of the ‘Kalbarri pair’ had sired a rock-wallaby with a Wheatbelt female. The research team was also “delighted to get large numbers of recaptures from both of the earlier releases with wallabies in good condition and most females carrying pouch young”.
Those who worked on the translocations – Parks and Wildlife officers from the Wheatbelt, Midwest and Pilbara regions, and the DBCA Biodiversity and Conservation Science staff, as well as WWF staff, Kalbarri Bush Ranger cadets and numerous volunteers – and the community at large can be optimistic that, with continued monitoring and fox and feral cat control, rock-wallabies will remain a feature of Kalbarri National Park for many years to come.
FURTHER INFORMATION
Joint authors of this report and their roles at the time were:
David Pearson, DBCA principal research scientist; Mike Paxman, Kalbarri National Park senior ranger; Anthony Desmond, DBCA Midwest region nature conservation leader; Jazmin Lindley, Merredin district assistant operations officer; and Juanita Renwick, DBCA senior zoologist.
More information can be found on the DBCA website www.dcceew.gov.au/environment/biodiversity/threatened/action-plan/priority-mammals/brush-tailed-rock-wallaby
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