Assessment of non-target impact of 1080-poisoning for vertebrate pest control on weta (Orthoptera: Anostostomatidae and Rhaphidophoridae) and other invertebrates in artificial refuges

Artificial refuges and mark-recapture techniques were used to monitor the non-target impacts of handbroadcast application (simulating aerial application) of Wanganui No.7 cereal-based baits containing 0.15% (1500 µg g-1) 1080 on populations of weta and other invertebrates in Tararua Forest Park, North Island, New Zealand. Wellington tree weta (Hemideina crassidens) and a cave weta (Isoplectron sp.) were the only species of weta that occupied the refuges. Flatworms, slugs, spiders, harvestmen, amphipods, millipedes, centipedes, cockroaches, and beetles also occupied the refuges. Invertebrate numbers in the refuges were monitored for 12 months before and 4 months after bait application on 22 August 2000. Bait application had no significant impact on the numbers of either species of weta, or on slugs, spiders, and cockroaches, the most numerous other invertebrates occupying the refuges. Bait application also had no effect on the number of individually marked tree weta resighted in the refuges. Few weta or other invertebrates were observed on baits at night. The concentration of 1080 in a cave weta collected alive from a bait, and in a tree weta collected alive from outside an artificial refuge, was less than 10% of the average lethal dose. The results indicate that 1080-poisoning for vertebrate pest control is unlikely to have any negative impact on populations of weta or the other invertebrates monitored.