Nine forest grids sampled via chew-cards and live-trapping for rats (Rattus spp.) during June 2018–August 2019 on Guam (G1–4) and Rota (R1–5) in the Mariana Islands. In the inset map, the red rectangle indicates the location of the two islands in the western North Pacific Ocean. In the main map, the blue circles indicate 11 × 11 grids with 12.5-m intervals between each station (grid area = 1.56 ha), and orange circles indicate 10 × 10 grids with 10-m intervals between each station (grid area = 0.81 ha).