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Top predator decline, mesopredator release and disease transmission: The case of the Tasmanian devil, feral cat and toxoplasmosis

International Congress for Conservation Biology

Auckland, New Zealand

5-9 December 2011



Tracey Hollings1
Menna Jones1
Nick Mooney 3
Hamish McCallum

1 University of Tasmania, Hobart, TAS, Australia
2 Griffith University, Brisbane, Australia
3 Department of Primary Industries, Parks, Water and Environment, Hobart, TAS, Australia.

Tasmanian devil populations are being devastated by devil facial tumour disease (DFTD), a consistently fatal transmissible cancer. Where the disease has been present for a decade or more, population declines of up to 94% have occurred. Evidence is emerging of feral cat increases in many areas of Tasmania, which may be a consequence of declining devil densities. Feral cats are of immense concern within the Australian environment, not only with the risk they pose to native wildlife through predation, but also as they are the only known definitive host of the coccidian parasite, Toxoplasma gondii.  Australia’s native wildlife has not evolved in the presence of cats or their parasites.

We are assessing whether native species are at increased risk of contracting toxoplasmosis in areas where populations of feral cats have increased following devil decline. We tested native species for toxoplasmosis antibodies in areas of varying cat densities. The highest toxoplasmosis seroprevalence in pademelons occurred in areas where cat density was the highest, being almost 5 times higher than in regions with the lowest cat densities. The highest prevalence was observed in eastern quolls which reached 59% in high cat density areas. Mesopredator release of cats may be a significant issue for conservation of native species, not only from increased predation pressure but through transmission of toxoplasmosis whose population level impacts on native wildlife are currently unknown.