KOALA NEWS & SCIENCE
An informative monthly newsletter about successes & important announcements in koala conservation, and the latest scientific publications about koalas.
March 2025
Subscribe here: https://mailchi.mp/808fc4af1ee0/koala-news-science
Wild Koala Day is on 3 May 2025 – the same day as the federal election!
We already have a heap of great events going on – see here: https://www.wildkoaladay.com.au/whats-on/. Let me know if you are planning an event so we can help promote it.
The theme this year is The Koala Election. #KoalaElection
We’ll be soon sending out an email to all the groups involved in past Wild Koala Days, with some guidance on ACNC charities and what political activities are allowed. If you’re not on that mailing list and want to be, email us here: wildkoalas@outlook.com
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Latest Koala Science
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McLennan, E.A., Wilmott, L., Madden, K., Belov, K. and Hogg, C.J., 2025. Low genetic diversity and high inbreeding in one of the last chlamydia-free strongholds for New South Wales koalas. Conservation Genetics, pp.1-13. https://link.springer.com/article/10.1007/s10592-025-01682-6
The genetic consequences of population isolation include inbreeding, genetic diversity loss and loss of adaptive potential. Koalas across south-western Sydney (New South Wales, Australia) may be vulnerable to isolation due to major roads and cleared forest. A few sites within south-western Sydney are some of the last chlamydia-free sites for koalas. Low genetic diversity and potentially low adaptive potential could lead to local extinction of these chlamydia-free sites. Using reduced representation sequencing, we assessed population differentiation, genetic diversity, relatedness, inbreeding, and gene flow across seven sites in south-western Sydney and the Southern Highlands. We found south-western Sydney koalas had significantly lower diversity, higher relatedness and inbreeding than Southern Highlands koalas. There was no evidence of contemporary gene flow from the more genetically diverse Southern Highlands sites into south-western Sydney. The separation between south-western Sydney and the Southern Highlands likely explains the lower genetic diversity among south-western Sydney sites. It may also explain why chlamydia is yet to reach these sites. However, there is evidence of a disease-front movement of chlamydia from Wingecarribee up into Wollondilly which has high gene flow with Campbelltown, a chlamydia-free site. While gene flow from south to north is low, the risk of chlamydia entering the chlamydia-free sites from a few migrants is notable. With possible low adaptive potential of south-western Sydney sites, a new threat of chlamydia entering the system may lead to population declines in these stronghold areas.
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Levengood, A.L., Hohwieler, K., Powell, D. and Cristescu, R., 2025. Age is just a number: No impacts of scat aging on SNP genotyping using a target capture approach. https://www.authorea.com/doi/full/10.22541/au.174264853.38473239
Recent advances in DNA sequencing and genotyping technologies are rapidly building our capacity to address ecological, evolutionary, and conservation questions for wildlife. However, wildlife genetic research increasingly relies on samples containing low quantities and quality of DNA, such as non-invasive, archival, and environmental DNA. These samples present unique methodological challenges; for samples collected in the wild, it is important to understand the impact of environmental exposure time or sample ’age’ on DNA quality and downstream genetic analyses. Here, we aged koala (Phascolarctos cinereus) scats under natural conditions and quantified DNA degradation. We assessed the effect of age on genetic data quality by measuring the proportion of missing single nucleotide polymorphism (SNP) data using DArTCap, a targeted genotyping methodology hypothesised to tolerate degraded DNA. Contrary to other studies, we found koala scat age was not a significant predictor of genotyping quality (i.e., rate of missing SNP calls) in the first 10 days of environmental exposure. We yielded high quality data from 10-day-old scats, but also low-quality data from fresh scats. This study is the first to investigate the effect of scat age on genotyping success using a targeted approach, and DArTCap specifically. These findings support the use of targeted genotyping (such as DArTCap) from scats and provide insights for future research using DNA from non-invasive samples. Targeted genotyping may extend the timeframe from which accurate data can be obtained from non-invasive samples, increasing potential sample sizes and enhancing our ability to address important questions in population ecology, conservation genetics, and population management.
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De Cahsan, B., Sandoval Velasco, M., Westbury, M.V., Duchêne, D.A., Strander Sinding, M.H., Morales, H.E., Kalthoff, D.C., Barnes, I., Brace, S., Portela Miguez, R. and Roca, A.L., 2025. Road to extinction? Past and present population structure and genomic diversity in the koala. Molecular Biology and Evolution, p.msaf057. https://doi.org/10.1093/molbev/msaf057
Koalas are arboreal herbivorous marsupials, endemic to Australia. During the late 1800s and early 1900s, the number of koalas declined dramatically due to hunting for their furs. In addition, anthropogenic activities have further decimated their available habitat, and decreased population numbers. Here, we utilise 37 historic and 25 modern genomes sampled from across their historic and present geographic range, to gain insights into how their population structure and genetic diversity have changed across time; assess the genetic consequences of the period of intense hunting, and the current genetic status of this iconic Australian species. Our analyses reveal how genome-wide heterozygosity has decreased through time and unveil previously uncharacterised mitochondrial haplotypes and nuclear genotypes in the historic dataset, which are absent from today’s koala populations.
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Funnell, O., McLelland, J., Kokosinska, A., Stephenson, T., Dunstan, E., Turner, B. and Speight, N., 2025. Prognostic factors in bushfire‐affected koalas–Kangaroo Island bushfire response 2020. Australian Veterinary Journal. https://doi.org/10.1111/avj.13434
This study presents a retrospective analysis of clinical records data from koalas presenting for treatment following the large-scale bushfire event on Kangaroo Island 2019–2020. The aim of the study was to identify prognostic factors for koalas affected by bushfire. Koalas (n = 199) were grouped based on their burn status in combination with their burn bandaging requirement at triage; those with no burns, with burns that did not require bandaging and with burns that did require bandaging. Overall, 59.8% of koalas had positive outcomes, but this reduced to only 13% of koalas in the most severely affected group (burns that were bandaged). Negative outcomes were found to be associated with several factors, including the timing of presentation, with the worst affected animals presenting in the first 2 weeks of the operation. Also, an increasing number of bandage changes during hospitalisation led to increasingly negative outcomes, with no positive outcomes beyond three bandage changes. In addition, clear associations were found with patterns of burns on feet, with only 4% positive outcomes for animals with all 4 feet burnt. All bandaged koalas with severe dehydration had negative outcomes and body weights decreased over time for hospitalised animals from the most severely affected bandaged burn group. Mild serum sodium concentration elevation at triage was the only clinically significant blood abnormality for koalas with bandaged burns. Overall, this study identified key prognostic factors, particularly bandaging requirements and the number of feet burnt, that will enable more effective decision-making at triage and improve animal welfare outcomes.
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Sarovich, D.S., Jelocnik, M., Stewart, P., Pollak, N.M., Wong, J.S., Kunesh, C., Ojiako, C., Hanger, J., Gillett, A., Valenza, L. and Portas, T., 2025. Dominance of Vaccine‐Specific Chlamydia pecorum ompA Genotypes in Koalas From North‐Eastern Australia. Ecology and Evolution, 15(3), p.e70973. https://doi.org/10.1002/ece3.70973
Chlamydia pecorum is a significant cause of morbidity and mortality in koalas and a major contributor to population decline. Due to its crucial role in vaccine development and use as a strain typing tool, multiple studies have investigated the prevalence and diversity of the C. pecorum outer membrane protein A (MOMP), encoded by ompA. This prior work has shown that ompA genotypes vary across geographical regions, with multiple genotypes identified across Eastern Australia. Despite these earlier studies, our understanding of the diversity and distribution of MOMP remains incomplete. Here, we aimed to assess the geographical distribution, diversity, and temporal stability of the C. pecorum ompA across wild koalas infected with Chlamydia in north-eastern Australia. Full-length ompA sequences were generated from 226 samples collected from 173 unique animals from multiple koala populations over a 4-year time span. C. pecorum ompA genotypes F and G were the most common and were identified across all geographical regions. Genotype A was the next most common but mostly restricted to the South Brisbane region. In addition to two novel genotypes, rare genotypes, including livestock-associated types E58 and L1, and koala-associated H and I were sporadically identified. Comparison with historical ompA genotypes showed that the distribution of genotypes has remained stable over the past decade, suggesting limited selective pressure despite ongoing vaccination trials and management programmes. The stability of genotypes coupled with the identification of novel and livestock-associated genotypes underscores the importance of continued surveillance to inform future vaccine development and conservation strategies for koalas.
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Gates, K., Sandoval-Castillo, J., Beaman, J., Da Silva, K.B., Saltre, F., Belov, K., Hogg, C., Bradshaw, C. and Beheregaray, L., 2025. Genomic erosion and inbreeding in an abundant island population of koalas. Genomic_erosion_and_inbreeding_in_an_abundant_island_population_of_koalas/
The persistence of many threatened species depends on isolated habitat patches such as conservation parks, fenced reserves, and islands. While these ‘conservation arks’ provide refuge from many contemporary threats, they can also pose risks of genetic diversity loss and inbreeding depression, further exacerbating extinction risk. A pertinent exemplar is the Kangaroo Island koala population in South Australia, which originated from a few translocated founding individuals in the 1920s, but now sustains a large population with low prevalence of infectious disease. We investigated the extent and consequences of founder effects on genomic diversity, inbreeding and adaptive potential in Kangaroo Island koalas by comparing them with mainland Australia populations, using high-coverage whole genomes. Our findings support sharp, recent declines in effective population sizes (Ne) in both mainland and Kangaroo Island populations. However, Kangaroo Island koalas had much lower individual and population-level diversity. Together with longer and more numerous runs of homozygosity, and an increased proportion of realised genetic load, these results support the hypothesis that a severe bottleneck has contributed to inbreeding and maladaptation in Kangaroo Island koalas. While Kangaroo Island has the potential to conserve a viable population of koalas, we recommend genetic rescue to restore diversity and mitigate inbreeding depression in this isolated population. Our results emphasise the need for longitudinal genomic monitoring and genetic management to maintain long-term viability and resilience in potential conservation arks. Understanding the demographic history of such populations will help inform future conservation aimed at preventing genetic erosion and preserving biodiversity.
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Koala Science in brief
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Tsangaras, K., Mayer, J. and Greenwood, A.D., 2025. Crossing Wallace’s line: an evolutionarily young gibbon ape leukemia virus like endogenous retrovirus identified from the Philippine flying lemur (Cynocephalus volans). Scientific Reports, 15(1), p.9790. https://www.nature.com/articles/s41598-025-94582-1
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Yu, T., Blyton, M.B., Abajorga, M., Koppetsch, B.S., Ho, S., Xu, B., Hu, Z., Luban, J., Chappell, K., Weng, Z. and Theurkauf, W.E., 2025. Evolution of KoRV-A transcriptional silencing in wild koalas. Cell. https://doi.org/10.1016/j.cell.2025.02.006
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Tarlinton, R., Meers, J. and Young, P., Endogenous retroviruses: Biology and evolution of the endogenous koala retrovirus. Cellular and Molecular Life Sciences, 65(21). https://doi.org/10.1007/s00018-008-8499-y
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Craig, S., 2025. Rat‐Bite Fever. The One Health Model as Applied to Zoonotic Diseases, pp.176-179. https://onlinelibrary.wiley.com/doi/abs/10.1002/9781119985853.ch4.14
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Previous Koala News & Science here: https://www.wildkoaladay.com.au/koala-news-science/koala-news-science-jan-february-2025/
Written by Janine Duffy President, Koala Clancy Foundation.
with support from Cheryl Egan, Organiser, Wild Koala Day.
Please send your positive, important news & publications to president@koalaclancyfoundation.org.au before 29th of each month for possible inclusion.