Mouse catch rates in snap traps on Mana Island, expressed as catch per 100 corrected trap nights (Nelson and Clarke 1973). A. Catch rates over 12 consecutive months in 1981–82, showing the annual peak in mouse density in late autumn and early winter (data from Pickard 1984). B. May–June catch rates over time, showing increasing mouse numbers after grazing by farm stock was reduced and then eliminated (see Table 1 for data sources).