Anticoagulant poisons, especially the second-generation anticoagulant brodifacoum, are used worldwide to eradicate pest mammals from high priority nature sites. However, the potency and persistence of brodifacoum may present threats to non-target species. In New Zealand, most ecosystems lack native terrestrial mammals; instead, birds, reptiles and invertebrates fulfil key ecosystem roles. Introduced mammals represent the biggest threat to persistence of native species.
A long-life poison bait dispenser, consisting of a tree-mounted platform that dispenses a highly attractive liquid bait only when triggered by actions characteristic of a possum (Trichosurus vulpecula), was developed. The liquid bait formulation prevents deterioration due to the action of oxygen, moisture, bacteria and insects. The prototype is designed to dispense 100 lethal doses of poison, and is expected to last more than five years in the field without attention. The equipment is designed to avoid fouling by algae, debris or nesting insects.
Brown kiwi (Apteryx mantelli) in central Northland have been monitored for up to 32 months of sustained exposure to brodifacoum poison. The cereal baits were placed in bait stations to target brushtail possums (Trichosurus vulpecula). Annual survival of 55 radio-tagged adult kiwi in two poisoned forest patches has been high (95.9%), and similar to that in two nearby unpoisoned forest patches and in the patches before poison was used (95.3%).
Although many species of native invertebrates have been identified on toxic baits containing sodium monofluoroacetate (1080) following aerial operations for possum control, few quantitative data are available to determine the risk of primacy or secondary poisoning that may result from these exposures. This paper reports on a series of studies conducted to determine the risk of 1080 exposure to one such non-target insect, the native ant Huberia striata. Subsequent risk of secondary poisoning to insectivorous animals is extrapolated.