The Greater Bilby (Macrotis lagotis) is an iconic species of Australian marsupial. Once found throughout inland Australia, the Bilby is now threatened as a result of habitat loss, as well as competition and predation from introduced species. Conservation measures for the Bilby include several captive breeding programs. These programs aimed not just to increase the number of individual Bilbies but also to retain the genetic diversity that will be important for the long-term persistence of Bilby populations.

My colleagues and I evaluated the effectiveness of these programs to maintain genetic diversity, which is typically lost from small populations. We regularly sampled two captive Bilby populations over almost 10 years and then determined the level of genetic diversity using hyper-variable genetic markers (microsatellites) We found good news. Genetic diversity was maintained in both studied populations, over ~10 years, mainly as a result of the regular addition of new individuals. Also the overall level of genetic diversity in the captive Bilby populations was similar to that of wild Bilbies.

Dr Mark Eldridge with the frozen tissue collection
Dr Mark Eldridge with part of the frozen tissue collection in the Genomics Lab. Image: Stuart Humphreys
© Australian Museum

An interesting finding was that the studbook estimates of genetic diversity were overestimated in comparison to those calculated directly from the genetic data, and thus, levels of inbreeding were underestimated. This is probably because the original individuals used to establish the populations were assumed to have been unrelated when they might not have been.

Therefore to improve captive management, we would recommend that captive breeding programs validate their studbook estimates with genetic data. This study highlights the importance of replenishing captive populations with unrelated individuals, especially post-animal removal for reintroductions.

Dr Mark Eldridge
Principal Research Scientist, AMRI

Dr Emily Miller
Research Fellow, Sydney Medical School, University of Sydney and AMRI

More information:
Miller, E.J., Eldridge, M.D.B., Morris, K.D., Thomas, N. and Herbert, C.A. 2015. Captive management and the maintenance of genetic diversity in a vulnerable marsupial, the greater bilby. Australian Mammalogy 37: 170–181.

This research formed part of Emily Miller’s PhD at the School of Biological Sciences, University of NSW and the Australian Museum Research Institute. She was co-supervised by Dr Cathy Herbert, University of NSW (now at University of Sydney) and Dr Mark Eldridge, Australian Museum Research Institute.