Invasive species and Pacific island bird conservation: a selective review of recent research featuring case studies of Swinhoe’s storm petrel and the Okinawa and Guam rail
The growing number of biological invasions worldwide is now being accompanied by burgeoning successful alien species eradications on islands of increasing size, topography and habitat complexity. However, the extent of these achievements depends on the definition of success. In most cases, success or failure are measured in terms of the absence or presence of the target alien species. It is becoming increasingly evident that how the invaded ecosystems respond to eradications should also be assessed. This is because some eradications have been accompanied by unexpected population explosions of hitherto seemingly harmless (or undetected) introduced species, previously suppressed by the eradicated alien species. These unexpected chain reactions are sometimes referred to as “surprise effects”. We conducted an eight year study of plant and animal communities in a simple insular ecosystem invaded by ship rats (Rattus rattus) and domestic mice (Mus musculus). We assessed these communities for potential surprise effects following rodent eradication. Next we eradicated the rats and mice following a protocol tailored to the presence of other introduced species. We then continued to monitor changes to the ecosystem, a step too often missing after eradication programmes. We then assessed the success of our eradication in terms of: 1) absence of the eradicated species; 2) recovery of the ecosystem; and 3) absence of surprise effects.