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Aerial surveys of eastern grey kangaroos, Macropus giganteus, were conducted over the western edge of the wheat belt of southern Queensland in two wet years (1983 and 1984) and one year of average rainfall (1985). Because most kangaroos moved rapidly off crops shortly after dawn and returned shortly before dusk, flights within 15 min of dawn and dusk provided the best indicators of kangaroo crop usage. Very low densities were observed on mature crops in all years and on immature crops in the two wetter years. In July 1985, which was drier, a density of 11 kangaroos km-2 was recorded on immature crops. This density was comparable with that for all uncultivated land in the surveyed area. Close to undeveloped land, densities of 14-17 kangaroos km-2 were observed on crops.

In Bungunya district, on the inland fringe of the winter wheat belt in SE Queensland, 2 approaches to estimate crop losses attributable to eastern grey kangaroos (Macropus giganteus) were assessed during dry conditions. In 1986, an early-season survey established indices of kangaroo usage and crop damage within 250 m of paddock edges. The relationship between these data and final grain yield suggested a minimum reduction in yield associated with kangaroos of 8% for the district. In 1987, yields from exclusion and open plots were used to obtain a direct estimate of kangaroo-associated yield reductions. These indicated a difference in yield of between 10% and 17% for the study area, although not all of this may be associated with kangaroos. Results suggest significant crop losses attributable to kangaroos. However, because of the nature of the research and the assumptions relied upon, the findings provide a guide to the magnitude of losses rather than highly reliable estimate.

Kangaroo density estimates derived from aerial survey depend on the method of deriving sightability correction factors developed by Caughley. The method depends on five assumptions, some concerned with the mathematical properties of a model for sightability probabilities and others with deriving correction factors from this model. All these assumptions can be criticized. In addition, evidence on the performance of the method does not suggest that it is accurate. Published density estimates are less precise than indicated, and may include biases due to factors not considered in the correction factors used, e.g. seasonal conditions, time of day, and species differences. At present, no satisfactory alternative method of correction exists but, because inaccuracies may be large, continued use of the method requires much greater caution than has previously been shown. This is particularly relevant where density estimates are used to determine management procedures.

Aerial surveys of feral pigs in the Goondiwindi region of Queensland showed an overall observed density of about 1 per square kilometree. On mature wheat crops in October, up to four feral pigs per square kilometre were seen amidst substantial crop damage. Emus were less abundant and seen more evenly over all habitats at an average of 0.3 per square kilometre. Factors affecting sightability are discussed.