Carlo Pacioni DVM, MVS

Doctor of Philosophy Thesis

The population and epidemiological dynamics associated with recent decline of woylies (Bettongia penicillata) in Australia


  • Dr Adrian Wayne BSc (Hons) PhD, Department of Environment and Conservation, Science Division
  • Dr Peter Spencer BSc (Mar Biol/Zool) PhD,Murdoch University
  • Prof Ian Robinson BVSc, PhD, MACVSc (Epidemiology), Murdoch University
  • Dr Kris Warren BSc BVMS (Hons) PhD, Murdoch University

The woylie or brush-tailed bettong (Bettongia penicillata ogilbyi) has recently undergone a dramatic decline (approximately 80% between 2001 and 2006). The Woylie Conservation and Research Project (WCRP) was established to investigate possible causes of this decline including the hypothesis that predators and/or a disease may be a concomitant cause if not the primary cause(s). 

Dr Pacioni’s research formed a key component of the WCRP, by investigating attributes of woylie population health and ecology considered relevant for the recovery of the species. His research included the first formal assessment of disease risks potentially relevant to the declines, to enable a systematic evaluation and prioritize the allocation of resources. Dr Pacioni’s research also established haematological reference ranges for woylies, and recorded gender differences for some haematological parameters. Additionally, a virological investigation was carried out, based on results of the disease risk assessment and haematological analysis.

Genetic profiles of indigenous (extant wild populations) and translocated woylie populations were examined, to assess whether woylie populations were suffering from reduced genetic “health” as a consequence of the bottleneck that occurred after European settlement. In order to do this a preliminary investigation of the cross-species performance of 32 primer pairs was carried out to assess their suitability for use in this study, and to facilitate future ecological and genetic studies in bettongs and potoroos. Findings from the study indicated that genetics does not appear to be a contributing factor to the present woylie decline. However, concern was raised for some indigenous populations as well as some translocated populations which were identified to have a substantially reduced genetic diversity.

Important insights were gained into population structure, female philopatry, effects of habitat fragmentation and past and present connectivity between populations. The evidence of current gene flow within and between populations (i.e. up to 60 km) signifies that direct transmission of an aetiological agent would be possible throughout the whole Upper Warren region within the time frame experienced in the decline.

Population viability analysis (PVA) demonstrated that the main threatening process for woylie populations is the result of the interaction of various variables (in particular predation and inbreeding) that acquire particular strength together. The minimum viable population size estimated through PVA was consistent with the empirical evaluation based on molecular data (1,000-2,000 individuals). PVA was also used to quantify the minimum mortality rates necessary for the decline to occur.

Although no clear evidence was found to support an association between a disease and the woylie decline, indirect evidence suggested that a disease can not be completely dismissed as a possible cause of decline, in particular in association with predation. Haematological, serological and genetic information generated by this study greatly improved the available knowledge on the health and viability of woylie populations and represent baseline data that will enable monitoring and detection of changes in the health status in these populations, as well as contribute to the refinement of the disease risk assessment and quarantine protocols.

Dr Pacioni’s research provided suggestions for critical management decisions, which are now under consideration by the woylie recovery team.

Once available, this thesis will be accessible through Murdoch University's Digital Thesis collection -


  1. Pacioni C. and Spencer PB.S., 2010, Capturing genetic information using non-target species markers in a species that has undergone a population crash. Australian Mammalogy 32: 33-38.
  2. Pacioni C., Wayne A. F., and Spencer, P.B.S., 2010 Effects of habitat fragmentation on population structure and long distance gene flow. Journal of Zoology. Early view (online).

Copies of these manuscripts can be requested by contacting Dr Carlo Pacioni - Email:


  • 2009:     Wayne, A. F., Thompson, A., Reiss, A., Eden, P., Pacioni, C., Smith, A., Nicholls, P., Page, M., Van Weenen, J., Morris, K., Marlow, N. and Orell, P. Investigation of woylie (brush-tailed bettongs) population declines – a critical and challenging problem. In 'Proceedings of the Australian College of Veterinary Scientists, Scientific Meeting'. Surfers Paradise, Queensland, 2-4 July 2009 (Oral presentation).
  • 2008:     Reiss, A., Eden, P., Wayne, A. F., Pacioni, C., Nicholls, P. and Thompson, R. C. A. Veterinary investigation of population declines of the woylie (Bettongia penicillata) in south-west Western Australia. In 'Proceedings of the Australasian Wildlife Management Society, 21st Annual Conference '. Fremantle, Western Australia, 24-27 November 2008 (Oral presentation).
  • 2008:     Pacioni, C., Spencer, P and Wayne, A. F. Understanding woylie decline: a molecular perspective. In 'Proceedings of the Australasian Wildlife Management Society, 21st Annual Conference'. Fremantle, Western Australia, 24-27 November 2008  (Oral presentation).
  • 2008:     Pacioni, C., Spencer, P. B. S. and Wayne, A. F. Unravelling the contribution of genetics in the decline of the woylie. In 'Proceedings of the Wildlife Disease Association (Australasian section)'. Kioloa, New South Wales, 20-25 September 2008 (Oral presentation).
  • 2008:     Pacioni C., T. Ellis, G. Knowles and P. Eden. “Identification of potential diseases and risk assessment in relation to recent woylie declines”. Woylie Symposium, Perth, 14 February 2008 (Oral presentation).
  • 2008:     Pacioni C., P.B.S. Spencer and A. Wayne. “Conservation Genetics”. Woylie Symposium, Perth, 14 February 2008 (Oral presentation).
  • 2007:     Pacioni C., P.B.S. Spencer e A. Wayne. “Woylie (Bettongia penicillata ogilbyi) conservation genetics project”, WDA Australasia conference, Dryandra, 23-28 September 2007 (Oral presentation).
  • 2007:     Pacioni C., K. Warren, I. Robertson, P. Spencer e A. Wayne. A conservation conundrum: the population and epidemiological dynamics associated with recent decline of woylies (Bettongia penicillata) in Australia.”. Wildlife Disease Symposium, Perth, 14 July 2007 (Poster).

Collaborators (positions held at Dec 2010)

  • Dr Mike Bunce ancient DNA laboratory, Murdoch University.
  • Dr John Parkinson, Dr Mark O’Dea and Cameron Loomes. Western Australia Department of Food and Agriculture.
  • Dr Timothy Mahony and Jenny Gravel. Queensland Department of Primary Industry and Fisheries.
  • Dr Nicola J. Marlow and Neil D. Thomas. Department of Environment and Conservation, Science Division, Woodvale, Western Australia
  • Marika Maxwell. Department of Environment and Conservation, Science Division, Manjimup, Western Australia
  • Dr Jason Van Weenen. Department for Environment and Heritage, Threatened Fauna Science & Conservation Division, Adelaide, South Australia


This research was undertaken with financial support provided by the Australian Academy of Science, South Coast Natural Resource Management Inc, the WCRP and DEC Science Division (PhD Student Stipend). 

Computer simulations were supported by iVEC through the use of advanced computing resources provided by the Informatics Facility located at Murdoch University

Haematological samples were processed at the Murdoch University Clinical Pathology Laboratory.

Photos provided by Carlo Pacioni

Department of Environment and Conservation