Sodium nitrite (NaNO2), a commonly used food preservative, has been researched in New Zealand for the control of brushtail possums (Trichosurus vulpecula). In sufficiently high doses, NaNO2 is toxic because it disrupts circulatory transport of oxygen. As NaNO2 is very bitter, encapsulation and mixing it through a highly palatable bait formulation is necessary to effectively deliver it to target pest species. In no-choice cage trials, 12/12 possums consumed a lethal dose of toxic paste bait and died on average after 95.6 minutes (±4.9 SE).
Pen and small-scale field trials have been completed on a new, long-life, resetting toxin delivery system for brushtail possums (Trichosurus vulpecula). Devices are designed to attract and control possums over long periods of time with minimal input and maintenance. The units are species-specific, lightweight, environmentally robust, and have the ability to control 100 possums before requiring servicing. Devices dispense a measured dose (0.8 g) of a palatable gel containing 12.5% zinc phosphide (Zn3P2) onto a possum’s abdomen.
When meat baits containing PAPP are applied in bait stations in field settings, stoat and feral cat numbers can be rapidly reduced. However, there has been limited practical experience with PAPP to date, especially when compared with alternative tools such as traps or sodium monofluoroacetate (1080) baits. Additional practical experience should enable the effective use of PAPP as a tool to help protect native species from introduced predators. In the future, PAPP will be developed in long-life bait and in a resetting toxin delivery system.
The risks to non-target species of a newly developed bait containing either 0.15% 1080 or 0.6% cholecalciferol in a gel matrix were assessed. Very few of them ate gel bait. The safety of the gel bait is further enhanced by its placement in the purpose-designed bait station from which little spillage occurs, and which can be placed so that it is out of reach of most non-target animals. Comparative data show that nontarget species are considerably less susceptible to cholecalciferol than to sodium monofluoroacetate (1080).