No abstract

Sustainable management of pastures requires detailed knowledge of total grazing pressure, but this information is critically lacking in Australia’s rangelands where livestock co-occur with large herbivorous marsupials. We present the first comparative measure of the field metabolic rate (an index of food requirement) of Australia’s largest marsupial, the red kangaroo (Macropus rufus), with that of domestic sheep (Ovis aries; merino breed). We tested the assumption that the grazing pressure of red kangaroos is equivalent to 0.7 sheep, and show this to be a two-fold overestimation of their contribution to total grazing. Moreover, kangaroos had extraordinarily lower rates of water turnover, being only 13% that of sheep. Consequently, our data support arguments that the removal of kangaroos may not markedly improve rangeland capacity for domestic stock. Furthermore, given the low resource requirements of kangaroos, their use in consumptive and non-consumptive enterprises can provide additional benefits for Australia’s rangelands than may occur under traditional rangeland practices.

Telemetry studies of feral pigs (Sus scrofa, L.) in different habitats were used to predict home range size, from (i) body mass and (ii) population density. Geometric mean regressions of the loge transformed data indicated that body mass of male and female feral pigs and mean population density were good predictors of the home range size of feral pigs (r 2 ϭ 0.81, 0.77 and 0.85 respectively). There were no sexual differences in home range size of feral pigs once the effect of body mass was taken into account. Use of these variables in models that incorporate spatial aspects along with the practical application of the results to the management of feral pig populations are briefly discussed.

The degradation of 1080 in buried Foxoff® baits was investigated. Baits were exposed to 5 different treatments: shelf-stored controls, prevailing weather, no rainfall, average weekly rainfall and twice average weekly rainfall. Curvilinear regression models were used to model the rates of decay of 1080. These predicted that under normal rainfall conditions, baits would become non-lethal to working dogs at 2.2 weeks and foxes at 2.8 weeks. Management implications of these results are discussed.

Combining abundance data collected in designed field surveys with biophysical data derived from geographic information systems is a powerful way to investigate predictors of spatial variation in the abundance of wildlife. We used such an approach to evaluate hypotheses about factors influencing the abundance of sambar deer (Cervus unicolour Kerr, 1792), a large non-native herbivore, in south-eastern Australia. We developed a spatial model for the abundance of sambar deer faecal pellets in a 3650-ha area in the Upper Yarra Ranges, Victoria. We counted the number of sambar deer faecal pellets along 100 randomly located transects and used a geographic information system to estimate biophysical variables around each transect. We formulated our hypotheses about how those variables might affect the abundance of sambar deer pellets into 22 candidate models and used the deviance information criterion to identify the 'best' model(s). Because five models had strong support we used model averaging to generate a predictive model. The three variables included in the predictive model were aspect (abundance of pellets declined with increasing 'northerliness' and increased with increasing 'easterliness'), distance to water and elevation; the latter two variables were positively correlated and had a negative effect on the abundance of pellets. In contrast to previous models of sambar deer abundance in south-eastern Australia, our spatial predictions of the abundance of faecal pellets can be easily tested and updated. Our approach would be useful for modelling the abundances of other wildlife species at a range of spatial scales.