Brodifacoum was administered to possums at a sub-lethal dose of 0.1 mg/kg to assess its persistence in blood, muscle, and liver. Only 1 of 68 possums died at this dose level. However, significant increases in one-stage prothrombin (OSP) and activated partial prothrombin times (APP) confirmed that the possum is susceptible to the anticoagulant effects of brodifacoum. Trace amounts of brodifaooum were detected in plasma for 35 days. Substantial concentrations of brodifacoum were retained in the liver for 8 months. Much lower concentrations were also retained in muscle tissue. The persistence of brodifacoum raises concerns about the possible transfer of this compound through the food chain to humans, dogs, or wildlife.

The comparative plasma pharmacokinetics of iophenoxic acid was studied in the cat and brushtail possum (Trichosurus vulpecula) to evaluate the suitability of this compound as a bait marker in these species. In cats, a mean peak plasma concentration of 946 micro g per 100 ml was obtained after administration of 1.5 mg/kg of iophenoxic acid. However, at the same dose level in possums, mean peak plasma concentration was only 157 micro g per 100 ml. Even after administration of 10 mg/kg of iophenoxic acid, the maximum peak plasma concentration in possums was only 459 micro g per 100 m/litre. The plasma elimination half-life for iophenoxic acid was 107 days in cats and close to one day in possums. Iophenoxic acid is therefore a suitable marker for cats but is unsuitable for use as a long-term or quantitative bait marker for possums. Differences between the possum and other mammals in gastrointestinal physiology and plasma protein configuration by account for the poor absorption and rapid elimination of iophenoxic acid in the possum.

As part of assessments of the palatability of different formulations for baits to be used for the control of feral goats, iopanoic acid and iophenoxic acid were compared as bait markers. After goats ingested iopanoic acid (25, 50 and 100 mg/kg), peak plasma iodine concentrations (4.86, 17.25 and 19.11 micro g/ml respectively) were reached after 4 to 8 h, followed by rapid excretion. In contrast, iophenoxic acid (1.5 mg/kg) was more slowly absorbed but remained stable in the plasma at concentrations greater than 2.40 micro g/ml for 3months after ingestion. When goats were fed 10 marked leaves smeared with non-toxic petrolatum containing a total of 50 mg iophenoxic acid, plasma iodine concentrations were proportionally and significantly higher than in animals fed on marked leaf smeared with non-toxic petrolatum (total of 5 mg iophenoxic acid), indicating a potential for quantifying the amount of bait ingested. Iophenoxic acid, therefore, shows the greatest potential as a bait marker for goats, particularly for quantitative use in palatability and acceptance studies.

This study evaluates dental ageing techniques for feral pigs in northern South I., New Zealand. Ages of pigs were estimated by three techniques: tooth eruption and replacement on criteria calibrated from pen-reared American-bred European wild pigs; tooth eruption, development, and wear calibrated from known-age feral pigs from the study area; and annular growth in cementum of molariform teeth. All age estimations showed strong agreement with each other and with known ages. The eruption and replacement criteria were most useful for ageing pigs less than 30 months old, whereas the other two criteria were more suited to ageing pigs more than 30 months old. All permanent teeth of New Zealand feral pigs erupted 1-2 months earlier than in European and Malayan wild pigs, and permanent premolars erupted up to 4 months earlier than in Japanese wild pigs. Earlier eruption may reflect early onset of maturity in New Zealand pigs. The clarity of annuli observed varied between animals, but generally increased with age. Pigs from unforested habitat had a higher percentage of clearly defined annuli than those from forested habitat. This may be explained by a climatic or dietary factor.

In recent years, research has shown that iophenoxic acid is useful as a biomarker in mammals. Its potential was initially demonstrated in several species of carnivores but it has since been found to be suitable for use in two species of herbivore, goats (Capra hircus) and deer (Odocoileus virginianus). We investigated its suitability for use in European rabbits (Oryctolagus cuniculus) dosed at levels of 1.5, 5 and 10 mg kg-1. Mean plasma-iodine concentrations in these groups increased to 328, 989 and 1438 g per 100 mL, respectively, after three days. The half-life of IPA was greater than 25 days at all three doses and plasma iodine remained at 4–10 times baseline levels for 13, 15 and 17 weeks, respectively.