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Shifts in Invasive Rodent Communities

One of the greatest threats to native species and biodiversity is loss of habitat. Thus, restoring native habitats has become a key conservation activity around the world. One potential, unintended consequence of habitat restoration is a shift in invasive animal populations, potentially impacting the native plants and animals targeted for conservation.


To study the potential impacts of habitat restoration on invasive species, NWRC, U.S. Geological Survey and University of Hawaii researchers compared invasive rat and mice communities in a restored, native, dry forest and an adjacent non-native grassland on Maui, Hawaii. In the unrestored grassland, house mouse captures outnumbered black rat captures 220 to one. In contrast, in the restored native forest, rat captures outnumbered mouse captures by nearly five to one. The relatively recent native forest restoration increased rat abundance and also increased their total biomass in the restored ecosystem 36-fold while reducing mouse biomass 35-fold.


Researchers note such a community shift is worrisome because black rats pose a much greater threat than do house mice to native birds and plants, perhaps especially to large-seeded tree species. Land managers should be aware that without intervention, such shifts may pose risks to conservation goals.


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