Protecting rock-wallabies in Australia

This is the final article (article no. 7) in a series on animal conservation. Previous article: Emperor penguins, kings of ice. First article: 55 years of vicuna conservation.

Australia is home to many unique mammals because they have evolved in geographic isolation for millennia. Over 200 years ago, European colonists brought their own mammals to Australia, devastating this unique wildlife in ways that can still be seen today. One example is the rock-wallabies (Petrogale spp.), a group of 25 animal species and subspecies related to kangaroos. Australian scientists are monitoring rock-wallaby populations to ensure they remain safe from natural and human-caused threats. This article will describe those threats and how rock wallabies are being conserved.

Rock-wallaby habitat

As their name suggests, rock-wallabies are adapted to occupy specific rocky habitats, including outcrops, cliffs and caves. Since they are primarily nocturnal, these habitats provide shelter in the daytime. Rock-wallabies have modified foot pads to grip tricky surfaces and access places their predators cannot. Recent research found that for two rock-wallaby species, their abundance is associated with more complex and rocky habitats. Because their habitat type is so niche and they rarely migrate, one small disturbance could wipe out an entire rock-wallaby population. This is reflected by their protections under Australian law: five types of rock-wallaby are classified as ‘vulnerable’, six as ‘endangered’, and one as ‘critically endangered’. Thus, the complex habitat of rock-wallabies is both a blessing and a curse.

Threats to rock-wallabies

Rock-wallabies are vulnerable or endangered mainly because of invasive predators such as foxes, cats, and goats. After being introduced from Europe during colonisation, these predators have eaten many wallabies and scared the rest into foraging elsewhere. If predators live between two rock-wallaby populations, there will be less migration and interbreeding, reducing overall genetic health (Figure 1). In addition, rock-wallabies will not forage if predators are in an area, so they have limited food sources under high pressure (Figure 1). Combined with these indirect reasons, direct predation by invasive mammals is the biggest threat to rock-wallaby survival.

Invasive predators are not the only threats to rock-wallaby populations. Wildfires kill the plants that wallabies rely on for food and shelter, such as rock figs. For example, one wildfire in the 2019/2020 season destroyed about 38% of brush-tailed rock-wallaby habitat. The already dwindling rock-wallaby populations may disappear if the climate crisis makes wildfires less predictable and more severe. Native herbivores like the euro and invasive herbivores like goats may also compete with rock-wallabies for food. There is evidence that euros out-compete rock-wallabies when food supplies are limited, but no evidence for goats yet. Thus, fires and competition combine with invasive predators to endanger rock-wallabies.

Translocation and monitoring

Monitoring existing rock-wallaby populations and creating new ones by translocation are reducing the threats of predation, fire, and competition. Brush-tailed rock-wallabies were translocated to Grampians National Park in 2008, but most animals died by 2013. Scientists thought manually handling wallabies might make them stressed and more vulnerable to predators. From 2014 onwards, non-invasive monitoring procedures like cameras and faecal DNA monitoring reduced predation and increased the survival rate of young rock-wallabies. Meanwhile, black-flanked rock-wallabies were being translocated from four different source populations to Kalbarri National Park, hoping they would interbreed and create a new genetically diverse population. The project was successful, as microsatellite genotyping found that the translocated population had more heterozygotes and more alleles per locus than the source populations (Figure 2). This population is predicted to grow until at least 2028 because it is diverse enough to avoid the inbreeding mentioned earlier. The Grampians and Kalbarri translocations show the importance of careful monitoring and genetic considerations for conserving rock-wallabies.

Conclusion

After invasive mammalian predators have decimated rock-wallaby populations throughout Australia for over 200 years, wildfires and herbivore competition make survival even more difficult. Conservation efforts are made harder by the specific and limited habitats that rock-wallabies need. However, translocation efforts which consider genetic diversity and the stress of manual handling keep rock-wallaby populations afloat.

Written by Simran Patel

REFERENCES

Campbell, I. & Woods, S. (2013) Wildlife of Australia. Princeton, UNITED STATES: Princeton University Press.

Kleemann, S., Sandow, D., Stevens, M., Schultz, D.J., Taggart, D.A. & Croxford, A. (2022) Non-invasive monitoring and reintroduction biology of the brush-tailed rock-wallaby (Petrogale penicillata) in the Grampians National Park, Australia. Australian Journal of Zoology. 69 (2): 41–54. Available from: https://www.publish.csiro.au/zo/ZO21009 (Accessed 10th December 2024).

Lavery, T.H., Eldridge, M., Legge, S., Pearson, D., Southwell, D., Woinarski, J.C.Z., Woolley, L.-A. & Lindenmayer, D. (2021) Threats to Australia’s rock-wallabies (Petrogale spp.) with key directions for effective monitoring. Biodiversity and Conservation. 30 (14): 4137–4161. Available from: https://doi.org/10.1007/s10531-021-02315-3 (Accessed 9th December 2024).

Morris, S.D., Johnson, C.N. & Brook, B.W. (2020) Roughing it: terrain is crucial in identifying novel translocation sites for the vulnerable brush-tailed rock-wallaby (Petrogale pencillata). Royal Society Open Science. 7 (12): 201603. Available from: https://royalsocietypublishing.org/doi/full/10.1098/rsos.201603 (Accessed 10th December 2024).

Nilsson, K., Pearson, D., Paxman, M., Desmond, A., Kennington, J., Byrne, M. & Ottewell, K. (2023) Translocations restore a population of a threatened rock-wallaby and bolster its genetic diversity. Conservation Genetics. 24 (5): 547–561. Available from: https://doi.org/10.1007/s10592-023-01520-7 (Accessed 9th December 2024).

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