What the study found
Arboreal herbivores such as the Common Brushtail Possum can act as incidental predators of bird eggs. In this study, possums did not show evidence of seeking out nests using odour or of individual specialisation.
Why the authors say this matters
The authors conclude that even low rates of incidental predation by native arboreal mammals can substantially increase extinction risk in small declining populations. They say this has implications for conservation globally and for understanding how herbivores can function as predators.
What the researchers tested
The researchers used artificial nest experiments to test whether possums use odour to find nests and whether low predation rates were explained by incidental predation or by specific individuals. They also used population viability analysis (PVA), a modelling approach for estimating extinction risk, to examine effects on a small declining bird population.
What worked and what didn't
The nest experiments found no evidence that possums seek out nests using odour and no evidence of individual specialisation. The results suggest possums were incidental predators of birds' eggs, with eggs consumed at 10% of sites. PVA modelling indicated that this low predation rate could still raise the threshold population density at which Allee effects, meaning reduced population growth at low density, lead to negative growth from 600 to 1000.
What to keep in mind
The abstract does not describe additional limitations beyond the scope of the experiments and modelling. The study focuses on one arboreal herbivore and one declining bird population, so the findings are specific to the cases described.
Key points
- Common Brushtail Possums were found to be incidental predators of bird eggs rather than nest-seeking specialists.
- Artificial nest experiments found no evidence that possums locate nests using odour.
- Possums consumed eggs at 10% of sites in the study.
- Population viability analysis suggested that low predation can still increase extinction risk in small populations.
- The modeled threshold population density for negative growth rose from 600 to 1000 when predation was included.
Disclosure
- Research title:
- Incidental possum predation can raise extinction risk
- Authors:
- Bianca McBryde, Catherine J. Price, Robert Heinsohn, Peter B. Banks
- Institutions:
- The University of Sydney, Australian National University
- Publication date:
- 2026-04-23
- OpenAlex record:
- View
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