Evidence that dingoes limit abundance of a mesopredator in eastern Australian forests
Johnson, CN and VanDerWal, J, Evidence that dingoes limit abundance of a mesopredator in eastern Australian forests , Journal of Applied Ecology, 46, (3) pp. 641-646. ISSN 0021-8901 (2009) [Refereed Article]
Aggressive behaviour of top predators may have strong effects on the distribution and abundance
of mesopredator species. Such interactions between predator species can reduce the intensity of
predation on vulnerable prey. Suppression of mesopredators by top predators is a potentially
important process that could protect small prey species from unsustainable predation.
There is some evidence that in Australia, the dingo
suppresses populations of the red
. This interaction could be signiﬁcant to biodiversity conservation because while
dingoes have been in Australia for several thousand years and coexist with a wide range of small
mammals, the fox is a recent arrival which has caused declines and extinctions, and continues to
threaten many prey species.
However the strength of the effect of dingoes on foxes is unclear, and some published data have
been interpreted as demonstrating no relationship between abundance of the two species. These
data come from forested habitats in eastern Australia, and may suggest that negative relationships
of dingoes and foxes do not occur in complex habitats.
We re-analyse published data on fox vs. wild dog (i.e. dingoes plus, potentially, feral dogs and
hybrids) abundance in eastern forests. These data reveal a triangular relationship of fox to wild dog
density: when wild dogs are abundant, foxes are consistently rare, while when wild dogs are rare,
foxes may be abundant but are not always so. This suggests that the abundance of wild dogs sets an
upper limit on the abundance of foxes, but does not fully determine fox abundance.
Standard regression and correlation methods are not appropriate for analysing such triangular
relationships. We apply two statistical methods that can be used to characterize the edges of data
distributions, and use these to demonstrate a negative relationship of maximum fox abundance to
the abundance of wild dogs.
Synthesis and applications
. Our analysis adds to evidence that dingoes may have negative effects
on red foxes in a wide range of habitats, and therefore, that dingoes may be signiﬁcant to conservation
of mammal biodiversity in Australia. It also illustrates problems and solutions in the statistical
analysis of abundance of one species as a function of the abundance of another species with which
it has a strong interaction.