KOALA NEWS & SCIENCE
An informative monthly newsletter about successes & important announcements in koala conservation, and the latest scientific publications about koalas.
January/February 2026
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National guidance for vaccination of koalas against chlamydia published online 23 February
The comprehensive document prepared by Wildlife Health Australia, has been published on the DCCEEW site. It covers all aspects of chlamydia vaccine for koalas, and is intended as a decision support tool for veterinarians, and koala managers.
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Latest Koala Science:
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Goldingay, R.L., 2026. Of droughts and flooding rains: koala population occupancy in a north-east New South Wales conservation reserve, and implications for range-wide surveys. Australian Mammalogy, 48(1), p.AM25030. https://doi.org/10.1071/AM25030
Population monitoring is fundamental to the conservation of threatened species such as the koala (Phascolarctos cinereus). This study extends by 2 years, a previous 8-year annual monitoring project of a koala population in north-east New South Wales. This study relied on audio-recorders and occupancy modelling to investigate whether the population has remained unaffected by the driest period on record followed by the wettest period on record. Audio-surveys were conducted at 42 sites over a 2-week period in each of 2022 and 2023. The probability of detection varied among types of audio-recorders, but averaged 0.45–0.88 per night, which equates to requiring 2–5 survey nights to have 95% confidence that koalas were detected. The probability of occupancy increased from 0.80 (95% CI, 0.66–0.94) in 2022 to 0.95 (95% CI, 0.89–1.0) in 2023. Local abundance of calling males detected by the more sensitive recorders increased from 1.6 ± 0.2 in 2022 to 2.2 ± 0.1 in 2023. The probability of occupancy when viewed across 10 years showed little change despite dramatic fluctuations in rainfall. This may reflect high local habitat suitability as well as occupancy being insensitive to variation in abundance because koalas are long-lived. Changes over time in the probability of detection may be more reflective of changes in abundance. This study highlights that the paucity of multi-year population studies on the koala means that our current understanding of koala population dynamics is inadequate for effective conservation.
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Pollak, N.M., Phillips, S., Kasimov, V., Ling, H., Wong, J.S., Rushton, B., Russo, L., Gillett, A., Valenza, L., Hanger, J. and Grosmaire, J., 2026. Chlamydia spp., Bordetella bronchiseptica, and Phascolarctid Gammaherpesvirus 1 and 2 Infections in Koalas (Phascolarctos cinereus) in South East Queensland, Australia: Detection in Healthy Individuals and Those with Signs of Respiratory or Other Disease. The Journal of Wildlife Diseases, 1(aop). https://doi.org/10.7589/JWD-D-25-00125
The decline in koala (Phascolarctos cinereus) populations has been significantly driven by infectious diseases, with chlamydial disease contributing to this trend. Chlamydia pecorum is often codetected with viruses such as phascolarctid gammaherpesvirus 1 and 2 (PhaHV-1 and PhaHV-2). Koalas can also be infected with other bacteria, including Bordetella bronchiseptica, which causes sporadic respiratory disease outbreaks. Respiratory infections and respiratory disease in koalas remain under-investigated. This study reports the detection of C. pecorum, Chlamydia pneumoniae, Chlamydia psittaci, B. bronchiseptica, PhaHV-1, and PhaHV-2 in 102 samples from 49 koalas that presented to veterinary facilities in South East Queensland, Australia from 2018 to 2023. The koalas included seemingly healthy individuals (n=21), koalas with respiratory disease (n=18), and koalas with other diseases (n=10). Overall, C. pecorum was detected in 37% of koalas, C. pneumoniae in 2%, C. psittaci in 0%, B. bronchiseptica in 18%, PhaHV-1 in 41%, and PhaHV-2 in 6%. Coinfections with three agents were common, particularly in koalas with signs of disease. Among the 18 koalas with respiratory disease, one was coinfected with four agents (B. bronchiseptica, C. pecorum, PhaHV-1, and PhaHV-2), and four were coinfected with three agents (B. bronchiseptica, C. pecorum, and PhaHV-1). Additionally, six koalas had coinfections involving two agents: two with C. pecorum and PhaHV-1, two with B. bronchiseptica and PhaHV-1, one with B. bronchiseptica and C. pecorum, and one with PhaHV-1 and PhaHV-2. Analysis of the genetic diversity of infecting chlamydial strains detected in koalas with respiratory and other diseases, based on the full-length ompA gene, identified previously characterized C. pecorum and C. pneumoniae ompA genotypes, as well as a unique C. pecorum ompA genotype. This study highlights the need for incorporating these infectious agents into koala respiratory diagnostics and emphasizes the need for continued research to investigate the complexities of these infections.
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Crowther, M.S., Rus, A.I., Mella, V.S., Krockenberger, M.B. and Mcarthur, C., 2026. Routine movement and resource tracking in a specialist arboreal folivore: sex-and season-dependent revisits by koalas. Journal of Mammalogy, p.gyaf094. https://doi.org/10.1093/jmammal/gyaf094
Routine movement, defined as the repeated use of space over time, can occur in both temporal and spatial dimensions and provides valuable insight into how animals interact with their environment. Temporal routine refers to consistent revisitation of resource patches, while spatial routine describes predictable sequences of patch use. Although well documented in nectar-feeding birds and insects, these behaviors remain poorly understood in mammalian herbivores. Here, we investigated temporal and spatial routine in the Koala (Phascolarctos cinereus), a specialist arboreal folivore, and assessed how intrinsic (sex, age) and extrinsic (rainfall, vegetation productivity) factors influence these patterns. From 2015 to 2017, we GPS-tracked 25 adult koalas for up to 5 mo in a fragmented agricultural landscape in northern New South Wales, Australia. Temporal routines were identified using Fourier and wavelet analyses of presence/absence time series within core areas, while spatial routine was assessed using a conditional entropy-based routine index. Most koalas exhibited temporal routines at 2-, 7-, or 20-d intervals. Males were more likely to show short (2-d) cycles, while females more often exhibited longer (20-d) cycles. The probability of temporal routine increased under conditions of low rainfall and reduced plant productivity, suggesting a behavioral strategy to access high-value resources during environmental stress. Spatial routine was observed in only 11 individuals and declined with increasing numbers of core patches, with overall spatial predictability not exceeding that expected under random movement. This study provides the first quantitative evidence of routine temporal and spatial movement in a specialist mammalian folivore, revealing sex-specific behaviors and the influence of environmental variability on movement patterns.
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Saltré, F., Peters, K.J., Rogers, D.J., Chadoeuf, J., Weisbecker, V. and Bradshaw, C.J., 2026. Balancing High Densities and Conservation Targets to Optimise Koala Management Strategies. Ecology and Evolution, 16(1), p.e72470. https://doi.org/10.1002/ece3.72470
Conservation management becomes complicated when globally threatened species reach high densities locally, exceeding the carrying capacity of the ecosystem and causing damage. Managing high-profile native species is particularly challenging, because ethical debates and public opposition to traditional control methods often prompt shifts toward strategies that prevent environmental harm rather than reducing populations. The koala (Phascolarctos cinereus) in South Australia exemplifies these challenges because, although it can damage the vegetation from high browsing pressure, culling is avoided due to public resistance. Therefore, managers have to consider costly and logistically constrained alternatives such as fertility control and translocation. Demographic models are valuable tools for predicting population dynamics, but their effectiveness depends on reliable population density estimates, often biased by expert-elicited and citizen-science data. We combined a point-process model, an ensemble species distribution model, and a demographic model to project koala populations in the Mount Lofty Ranges over the next 25 years to assess the efficiency and cost-effectiveness of fertility-control interventions while accounting for sampling biases, habitat suitability, and local densities. We tested two hypotheses: (1) koala distribution is driven by rainfall, temperature, and soil acidity, with summer rainfall boosting habitat suitability, and (2) spatially targeted fertility interventions in high-suitability areas are more cost-effective than generalised strategies due to subpopulation connectivity. Our models confirmed that these three environmental factors shape koala distribution and that, in the absence of intervention, the koala population could increase by ~17-25% in 25 years. Fertility control focusing on adult females emerged as the most cost-effective (~AU$34 million) strategy, although it was slower at reducing population size compared to an intervention also sterilising female back young. While the choice of sterilisation scenario has minimal impact on overall costs, ethical considerations and long-term conservation goals such as population density thresholds will have more influence on managing expenses effectively.
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Palacios, P.D., Sergura Forero, P.A., Gurkin, R.J., Smith, J.M., Campbell, Y., Johnston, S.D. and Gambini, A., 2026. 6 Impact of chilling, cryopreservation, and freeze-drying on DNA fragmentation and PLCζ expression in koala (Phascolarctos cinereus) epididymal spermatozoa. Reproduction, Fertility and Development, 38(1), p.RDv38n1Ab6. https://doi.org/10.1071/RDv38n1Ab6
The koala, an iconic Australian marsupial, is currently listed as endangered, primarily associated with habitat loss and disease. Recovering spermatozoa from deceased individuals enables genetic rescue and development of novel preservation strategies, given the limitations of current cryopreservation techniques in marsupials. Importantly, preservation methods must safeguard key sperm components such as DNA and phospholipase C zeta (PLCζ), which are essential for fertilization and embryo development. Thus, we designed 2 experiments: Exp. 1, to assess motility, viability, and PLCζ expression in epididymal spermatozoa chilled for up to 96 h, and Exp. 2, to compare fresh epididymal sperm with conventional freezing (CF) and freeze-drying (FD) on sperm quality, including DNA fragmentation. For Exp. 1, fresh epididymal sperm were recovered from three koalas by mincing one epididymis within 2 h postmortem (control) in Tris-citrate-glucose (TCG) with 1% antibiotic–antimycotic, incubated for 10 min at 35°C, while the contralateral epididymis was stored at 5°C in TCG and processed at 96 h. Sperm were assessed for motility and viability (SYBR-14/PI) under an epifluorescence microscope. PLCζ presence in the sperm head (PLCζ+) was evaluated by immunofluorescence using a rabbit polyclonal antibody (Arroyo-Salvo et al. 2024 Andrology12, 345–356). For Exp. 2, fresh epididymal sperm (control) recovered from three koalas were assessed and used for CF and FD, respectively: CF was performed in TCG with a final concentration of 14% (vol/vol) glycerol, equilibrated at 4°C for 1 h and loaded into 0.5-μL straws (2 × 106 sperm/mL). Straws were placed 5 cm above the surface of liquid nitrogen before being plunged and stored in liquid nitrogen. FD was performed in DMEM/F12 supplemented with 10 mM HEPES and 0.2 M trehalose. Aliquots (100 µL, 5 × 104 sperm/mL) were placed in glass vials, dried for 48 h at −50°C, 0.04 mbar, and stored at 5°C for one year. Quality parameters and DNA fragmentation were assessed using the Koala HaloSperm® kit in control, thawed (60 s at 35°C), and rehydrated samples. Statistical analysis was performed using an unpaired t-test or Tukey’s multiple comparison (P < 0.05). For Exp. 1, motility and viability did not significantly change after 96 h postmortem. However, PLCζ+ (mean ± SEM, %) was significantly lower at 96 h (66.7 ± 4.98) compared with the control (86.0 ± 4.51). For Exp. 2, motility differed significantly between control (67.7 ± 13.3) and CF (5.0 ± 3.6), and FD (0.0 ± 0.0), with no significant difference between CF and FD samples. Viability differed significantly among groups: control (79.7 ± 8.8), CF (31.0 ± 2.1), and FD (2.3 ± 0.3. Similarly, PLCζ+ levels varied significantly: control (89.0 ± 3.1), CF (53.0 ± 2.3), and FD (20.0 ± 3.6). DNA fragmentation levels also increased significantly from control (7.3 ± 1.5) to CF (27.3 ± 1.5) and FD (37.7 ± 0.3). Our findings revealed that chilled epididymal spermatozoa retained motility and viability up to 96 h postmortem, though PLCζ+ significantly declined. In contrast, CF and FD induced severe reductions in motility, viability, PLCζ+, and DNA integrity. This study represents the first attempt at freeze-drying koala spermatozoa and highlights the potential of chilled spermatozoa to remain viable for genetic recovery up to 96 h, providing a step forward in wildlife biobanking.
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Previous Koala News & Science here:
Written by Janine Duffy President, Koala Clancy Foundation.
with support from Cheryl Egan, Organiser, Wild Koala Day.
Please send your important news & publications to president@koalaclancyfoundation.org.au before 29th of each month for possible inclusion.