page 187

Kaingaroa and West Taupo Trials

In an attempt to reduce the labour content and apparent contagion between assessments two changes were made when the bait interference method was introduced to Kaingaroa and Western Bays, Taupo in 1976: (1) baits were set out and left over two nights before assessment; (2) there were only two baitings before and two after poisoning, separated by at least two weeks. All baits were removed between assessments. This kept the number of visits low and aimed to reduce or eliminate the rise in baits taken between assessments. Some preliminary trials were carried out at Kaingaroa in April/May but high variability in the data made the results inconclusive, so at Kaingaroa (but not Western Bays) bait interference assessment was run in parallel with mark/recapture trapping and spotlight counts. 1200 ha were assessed at Kaingaroa and 6800 ha at Western Bays in 1976. In each area 30 lines of 20 bait stations were used, and the results are shown in Table 1.

The method was unsatisfactory in failing to give a consistent estimate of relative density over the first two (pre-kill) assessments - in both areas there was a marked increase. Moreover at Kaingaroa the percent kill derived from bait interference was lower than estimates based on trapping and spotlight counts.