Radio collaring reveals long-distance movements of reinvading ship rats following landscape-scale control

Understanding rates of reinvasion is critical for determining what drives ship rat population recovery following large-scale control operations. We radio-tracked 23 adult ship rats on the edge of a forested area where rats had been suppressed by aerial compound 1080 in the Hollyford Valley, Fiordland. Eleven individuals died within two months of collaring and two individuals were never detected again, leaving us with data from 10 rats. Six individuals were recorded moving 70–174 m from their collaring sites over the nine month monitoring period, which is comparable to normal home range movements found by other studies. Four individuals were recorded moving 657–1516 m into the operational area (mean 1172 m). Sex was unrelated to whether individuals moved large distances or not. Our study confirms that ship rats may move large distances when at low density.