Attempts to reduce ecosystem damage by removing an invasive species that has become an area's top predator can allow populations of invasive prey species to grow, inadvertently worsening matters. Wendy Ruscoe at Landcare Research in Lincoln, New Zealand, and her colleagues report that changes among species that compete for resources such as food could have similar consequences.
In the forests of New Zealand's North Island, the team monitored populations of stoats (Mustela erminea; pictured left), the rat (Rattus rattus) that they prey on and one of the rat's competitors, the Australian brushtail possum (Trichosurus vulpecula; right) — all invasive species. When the authors killed off the possums, rats jumped in number. However, controlling the stoats had no effect on the rat population, indicating that competition was more important than predation.
The team suggests that the benefits of controlling possum numbers should be weighed up against the consequences of increased rat numbers.
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Competition counts. Nature 477, 135 (2011). https://doi.org/10.1038/477135e
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DOI: https://doi.org/10.1038/477135e
