A dangerous idea: that Koala densities can be low without the populations being in danger 

Robert Close1, Steven Ward1,2 and David Phalen

1 School of Science and Health, University of Western Sydney, Campbelltown, Locked Bag 1797, Penrith NSW 2751 Australia, NSW.

2 Eco Logical Australia, Level 6, 299 Sussex St. Sydney, NSW 2002 Australia.

3 Faculty of Veterinary Sciences, University of Sydney, NSW, NSW 2006 Australia.


The great public appeal of the Koala Phascolarctos cinereus gives it political power. Its appeal has been used successfully to publicise its vulnerability to the clearing of its habitat. The result is that the protected bushland also preserves habitat of numerous species that lack the Koala’s political influence. However, any research that indicates that the Koala is less vulnerable than is generally believed may lessen the species’ political power. The authors of such research may feel like traitors to the cause of ecological conservation. Nevertheless, several features of Koala ecology must be considered. Firstly, their sustainable density for any habitat is unknown. The fact that they were not discovered by European colonists during the first 10 years of settlement indicates that the original population density was very low near Sydney. Secondly, our observations of a low-density population at Campbelltown show that, in the absence of chlamydiosis, longevity and reproductive success are approaching maximal, as are dispersal rates. We believe that these factors have led to a local increase in numbers and distribution. Thirdly, it appears that the southern regions of NSW have a scattered distribution of very low-density populations. Distributions of these populations and the presence of linking vegetation may be more important to our notions of Koala survival than changes in actual numbers of animals.