rodenticide

We monitored 16 radio-tagged moreporks (Ninox novaeseelandiae) on Mokoia Island after a brodifacoum poison drop to eradicate mice (Mus musculus), normally included in the owls' diet. All 16 moreporks were alive after 13 days. One bird was found dead on day 22, and corpses of two radio-tagged birds were located on day 51. The bird found on day 22 contained 0.97 mg kg(-1) of brodifacoum in its liver. The other two carcasses were not analysed, but they probably died as a result of brodifacoum poisoning. Thus, three out of 14 birds died (21% mortality).

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.

The effectiveness of Feracol®, a possum control paste bait containing 0.8% cholecalciferol, as a rodenticide has been assessed in cage and field trials. Caged rats were provided with toxic bait in choice and no-choice tests. Feracol® was readily eaten when presented as the sole food source or with other food, and was effective at killing rats in both situations. Wild-caught and laboratory rats (n = 35), comprising both ship (Rattus rattus) and Norway rats (R. norvegicus), were presented with 30 g of Feracol® alone or with an equivalent toxic bait over 48 h.