Brodifacoum, an anticoagulant used in cereal-based baits for the control of vertebrate pests, especially rodents, may be accidentally ingested by non-target species. In birds, its acute toxicity varies from an LD 50 of < 1 mg/kg in pukeko to >20 mg/kg in paradise shelduck. Fourteen indigenous and eight introduced bird species have been reported killed by field use of brodifacoum in New Zealand. Populations of three species (western weka, Stewart Island weka, and pukeko) have been severely reduced in poisoned areas. There are no published data on the acute toxicity of brodifacoum in bats, reptiles, or amphibians. Invertebrates are unlikely to be killed by anticoagulants. Because of the high toxicity of brodifacoum, all vertebrates that eat baits or poisoned prey are at risk. Brodifacoum is only slowly eliminated from the liver, and therefore accumulates in vertebrates if there are repeated exposures to the toxin, which increases the risk of death. In New Zealand, indigenous non-target species most at risk from eating brodifacoum in cereal-based baits are herbivorous and omnivorous birds (e.g., weka, pukeko, and saddleback). The species most at risk from secondary poisoning are predatory and scavenging birds such as weka, Australasian harrier, southern black-backed gull, and morepork. Insectivorous birds, bats, lizards, and frogs are probably least at risk. However, laboratory and field trials are essential to determine the actual risks, and reduce scientific uncertainties. The risks of pest control must be carefully balanced against the benefits. These benefits can be substantial where introduced mammals threaten native species with extinction.

No abstract

Poison-baiting trials were carried out in Canterbury, Nelson, and Westland in 1986/87 to 1989/ 90 to reduce wasp (predominantly Vespu/a vulgaris) populations. Compound 1080 was mixed with canned sardine in aspic jelly for bait. Bait stations were put out in areas of 1.5-3 ha, at a density of about 40/ha. Wasps were pre-fed with non-toxic bait for at least 3 days before poisoning.Poison-baits containing 0.001% and 0.01% 1080 had no significant effect on wasp traffic at nest entrances, 0.1% 1080 reduced wasp traffic by 17%, 0.5% 1080 by 78%, and 1% 1080 by 89%. Reduction in wasp numbers after poisoning with 0.5% or 1% 1080 was rapid, up to 100% within 6 h. The level of reduction declined beyond 100m from bait stations. After poisoning, wasp traffic at nests within 100m of bait stations remained low for the rest of the season but partially recovered at nests more than 100 ~ from baits. Wasp numbers visiting bait stations containing non-toxic baits increased to about 30% of pre-poison levels 4 weeks after poisoning. These wasps must have come from nests more than 100 m from bait stations.Although 1080 in sardine baits effectively reduced wasp populations in local areas, a concentration of 0.5-~.0% was required. The hazard to non-target species was reduced by the bait being confined in bait stations and exposed for less than 6 h. However, 1080 is highly toxic to vertebrates, especially dogs, which imposes restrictions on its use. Alternative poisons that are less toxic than 1080 to non-target species need to be found. Z91007

The risks to non-target birds and other wildlife from the use of vertebrate pesticides, including anticoagulant rodenticides, are determined to a significant extent by species' intrinsic susceptibility, and the toxicokinetics of the compounds used. Brodifacoum is highly toxic to birds and mammals. The acute toxicity of brodifacoum to birds in New Zealand varies from <1 mg/kg in pukeko (Porphyrio p. melanotus), the native swamp hen, to >20 mg/kg in the paradise shelduck (Tadorna variegata). Like other second-generation anticoagulants brodifacoum is strongly bound to vitamin K epoxide reductase and will persist, apparently for at least 6 months, in organs and tissue containing this enzyme, e.g., liver, kidney, and pancreas. The unique toxicokinetics of this class of compound exacerbates the risk of primary and secondary poisoning of non-target species. Vertebrate pest control programmes in New Zealand using bait containing brodifacoum have resulted in the primary and secondary poisoning and sub-lethal contamination of non-target species. These include native raptors, such as the Australasian harrier (Circus approximans) and morepork (Ninox novaeseelandiae), other native birds such as the pukeko, weka (Gallirallus australis), southern black-backed gull (Larus dominicanus), and kiwi (Apteryx spp.), and introduced mammals, including game animals. There are increasing numbers of reports worldwide of wildlife contamination and toxicosis after the use of second-generation anticoagulants. All pest control activities require careful risk-benefit assessment in view of their potential to cause adverse environmental impact. Monitoring of wildlife for pesticide residues will provide data that can be used to reduce the risk of anticoagulant bioaccumulation and mortality in non-target species.

Protein bait preferences of wasps (Vespula vulgaris and V. germanica) were determined by measuring the number of wasps attracted to different bait types, the amount of each bait type collected by wasps, and the proportion of wasps collecting bait. Fresh fish and meat baits attracted the largest number of wasps, but canned sardine cat-food was collected in the greatest amounts. Factors influencing attraction of wasps to sardine cat-food included wasp density, season, and weather. The number of wasps attracted to sardine cat-food increased rapidly in January but lagged behind the number of wasps flying in and out of nests, peaked later, and declined earlier. The proportion of wasps that returned to nests carrying sardine cat-food peaked in February-March, when it was higher than the proportion collecting natural protein food. Sardine cat-food is currently the best bait to use for wasp control because of its attractiveness, palatability, and acceptability to wasps. Future research should investigate other methods besides freezing for prolonging the shelf-life of sardine cat-food baits, and the use of solvent extracts of sardine cat-food to prolong the field-life of baits.