retention

The field use of brodifacoum baits (Talon(R) and Pestoff(R)) to control brushtail possums (Trichosurus vulpecula) has increased in recent years. This has raised concerns of secondary and tertiary poisoning, resulting from the transfer of this toxicant through the food chain. In New Zealand, feral pigs (Sus scrofa) are known to scavenge possum carcasses and and may also gain access to bait stations containing possum baits. We have determined the concentrations of brodifacoum in muscle and liver tissue from captive pigs after primary and secondary poisoning.

Aerial poisoning using Talon(R) 7-20 baits (active ingredient 20 ppm brodifacoum) was carried out on Motuihe Island, Hauraki Gulf, during the winter of 1997. The operation aimed to eradicate Norway rats (Rattus norvegicus) and house mice (iMus musculus) and to reduce rabbit (Oryctolagus cuniculus) numbers significantly. We studied the diet of feral house cats (Felis earns) before the operation, then monitored the impact of the operation on them to determine whether secondary brodifacoum poisoning caused a reduction in their numbers.

The impact of discharging an oxidation pond effluent into a wetland in the Waitangi Forest (Northland) was assessed by comparing the water, soil, and vegetation of this wetland (the sewage wetland) with that of an adjacent wetland not receiving effluent (the reference wetland). The hydroperiod of the two wetlands differs markedly with the sewage wetland now permanently flooded whereas the reference wetland is subject to summer drawdown. Marked differences were found in gross chemical indicators such as pH and redox potential between the soils of the 2 wetlands.