When less is more: a comparison of models to predict fluoride accumulation in free-ranging kangaroos.

Vegetation contaminated by industrial fluoride emissions can cause disease in herbivorous mammals. Spatially explicit exposure models offer a quantitative approach for evaluating and managing the potentially toxic effects of chronic fluoride consumption on wildlife. We monitored eastern grey kangaroos (Macropus giganteus) inhabiting a high-fluoride environment in the buffer zone of an aluminium smelter in southeastern Australia between 2010 and 2013. We measured fluoride levels at 19 pasture sites and determined the foraging range of 37 individual kangaroos. A series of generalised linear models were developed to estimate bone fluoride accumulation as a function of pasture exposure. Model outputs were compared to identify the most appropriate predictive tool for kangaroo bone fluoride accumulation relative to exposure. Accounting for age there was a negative association between bone fluoride concentration and distance of the central emission point from both the mean centre of foraging range and the point of death. The mean foraging range centre was the best predictor, with point of death just as suitable (and simpler), whereas more complex parameters such as monthly and cumulative fluoride exposure were poor predictors of bone fluoride concentration. The more complex dietary fluoride exposure estimates did not improve predictive capability compared with the simple, spatial models. We conclude that in actively managed wildlife populations, simple, locally validated models can provide estimates of bone fluoride accumulation sufficient to support decision-making.

Interspecific variation in the diets of herbivores in an industrial environment: implications for exposure to fluoride emissions.

Atmospheric fluorides (gaseous and particulate) are deposited on, and absorbed by, vegetation. Ingested fluoride accumulates in calcified tissues of vertebrates, and if it is excessive, it may lead to dental and skeletal fluorosis. The prevalence, form and severity of the effects vary greatly between species. Foraging strategy can be an important determinant of fluoride exposure in herbivores, because foliar fluoride concentrations vary between plant species, for example, according to vertical and lateral position in the vegetation. We combined microhistological analysis of diet and analysis of foliar fluoride levels to examine interspecific variation in dietary fluoride exposure of macropodid marsupials (swamp wallaby Wallabia bicolor, red-necked wallaby Notamacropus rufogriseus and eastern grey kangaroo Macropus giganteus), in the buffer zone of an aluminium smelter in Victoria, Australia. Dietary niche differentiation between species was evident. The swamp wallaby and the red-necked wallaby were browsers or mixed feeders, depending on the classification system used. The eastern grey kangaroo was a grazer, consuming almost entirely grasses. However, foliar fluoride did not vary significantly between the main plant groups consumed. Our results indicate that interspecific variation in diet at this site is unlikely to explain variation in fluoride exposure.

Pharmacokinetics of moxidectin in the southern hairy-nosed wombat (Lasiorhinus latifrons).

Sarcoptic mange, caused by Sarcoptes scabiei var. wombati, could be a significant threat to populations of southern hairy-nosed wombats (Lasiorhinus latifrons; SHNW) in Australia. Treatment is currently based on the off-label use of various parasiticidal drugs, with limited clinical efficacy trials. Our primary aim was to determine the pharmacokinetic parameters of a macrocyclic lactone, moxidectin, to assist in the development of effective treatment protocols. Pharmacokinetic parameters were determined in four female SHNW following a single subcutaneous injection of 0.2 mg/kg moxidectin. Blood samples were collected for 38 days following injection (August-September 2008), for analysis using liquid chromatography and tandem mass spectrometry. The mean peak plasma concentration occurred at 13.6 hr, with a mean peak plasma level of 98.6 ng/ml. The mean elimination half-life was 5.03 days, resulting in a mean area under the curve of 377 ng.day/ml. The peak plasma moxidectin concentration was higher than that seen in livestock species but the plasma elimination half-life was shorter. This study suggests that a single injection of 0.2 mg/kg moxidectin may not be sufficient to clear a mange infection in this species.