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We describe a landscape‐scale study of fragmentation effects on arboreal marsupials at Tumut, southeastern Australia. Embedded within a 55000‐ha plantation of exotic Monterey pine (Pinus radiata) are 192 patches of remnant Eucalyptus forest, with large contiguous areas of eucalypt forest beyond the plantation boundary. We compared presence and estimated abundance of arboreal marsupials in three broad groups of sites: remnants of native Eucalyptus forest in the P. radiata plantation; P. radiata stands in the plantation; and large areas of contiguous Eucalyptus forest surrounding the plantation. The study animals were Trichosurus vulpecula, T. caninus, Petaurus breviceps, P. norfolcensis, P. australis, Acrobates pygmaeus, Pseudocheirus peregrinus, and Petauroides volans. We used randomized, replicated statistical procedures to sample 86 eucalypt remnants varying in size, shape, and other features. We matched 40 sites in large contiguous Eucalyptus forest to those remnants, based on environment, climate, terrain, and vegetation cover. In addition, 40 sites in P. radiata stands were matched to sites in the remnants and the large eucalypt forest on the basis of geology, climate, and terrain. We also surveyed 41 micropatches (remnants < 1 ha), where almost no animals were detected. These micropatches, smaller than the home ranges of most arboreal marsupials in the Tumut region, probably represent a minimum threshold patch size below which animals cannot survive. Highly significant landscape context effects were identified. P. radiata sites were excluded from analysis because few animals were detected there. P. australis and P. norfolcensis were not recorded in remnants. P. norfolcensis was recorded only once in contiguous eucalypt forest; P. australis was absent. Four species (P. volans, P. peregrinus, T. vulpecula, and T. caninus) occurred in sufficient numbers for statistical analyses of presence and abundance on remnants vs. large contiguous forest. P. volans was less likely to occur in remnants, whereas P. peregrinus was less likely to occur in contiguous eucalypt forest. Site context had no significant effect on presence of T. caninus, and arboreal marsupials per se, or on abundance of P. volans, T. vulpecula, T. caninus, and arboreal marsupials overall. P. peregrinus was significantly more abundant in remnants than in contiguous eucalypt forest. Statistical adjustment for environmental, climatic, terrain, and vegetation variables by regression modeling did not change animal abundance results. Similar outcomes were recorded for presence of T. vulpecula and T. caninus. However, context effects for presence of T. vulpecula, P. volans, and P. peregrinus could be explained by some of the vegetation, terrain, and landscape covariates. For P. volans, probability of occurrence was significantly greater in large remnants, sites on flat terrain, and sites dominated by particular eucalypt forest types. T. vulpecula was significantly more likely to occur in large remnants and sites with open understories. There was no evidenc...

There is a growing debate about the ability of Population Viability Analysis (PVA) to predict the risk of extinction. Previously, the debate has focused largely on models where spatial variation and species movement are ignored. We present a synthesis of the key results for an array of different species for which detailed tests of the accuracy of PVA models were completed. These models included spatial variation in habitat quality and the movement of individuals across a landscape. The models were good approximations for some species, but poor for others. Predictive ability was limited by complex processes typically overlooked in spatial population models, these being interactions between landscape structure and life history attributes. Accuracy of models could not be determined a priori, although model tests indicated how they might be improved. Importantly, model predictions were poor for some species that are among the beststudied vertebrates in Australia. This indicated that although the availability of good life history data is a key part of PVA other factors also influence model accuracy. We were also able to draw broad conclusions about the sorts of populations and life history characteristics where model predictions are likely to be less accurate. Predictions of extinction risk are often essential for real-world population management. Therefore, we believe that although PVA has been shown to be less than perfect, it remains a useful tool particularly in the absence of alternative approaches. Hence, tests of PVA models should be motivated by the cycle of testing and improvement.

This paper examines home-range attributes of 40 greater gliders (Petauroides volans) in five patches of remnant eucalypt forest surrounded by stands of radiata pine (Pinus radiata) near Tumut in south-eastern Australia. Fixed-kernel smoothing methods were used to estimate home-range size for P. volans. For males, home-range size varied from 1.38–4.10 ha (mean = 2.6 ± 0.8 ha, n = 12) and was significantly larger (P < 0.05) than for females (1.26–2.97 ha, mean = 2.0 ± 0.6 ha, n = 11). Home-range size increased significantly with increasing patch size and reduced patch population density. Thus, small patches had more animals per unit area with smaller home ranges and greater home-range overlap. Our findings illustrate flexibility in the use of space by P. volans. Such results have not previously been reported for P. volans or any other species of arboreal marsupial. Considerable home-range overlap (at 95th percentile isopleth level) was observed between male and female P. volans. Pairs of females also exhibited home-range overlap. Males tended to maintain home ranges exclusive of other males, although some shared common areas. Contrary to the large variations observed in home-range area, core areas (50th isopleth) remained relatively constant, regardless of patch size, population density or sex. This may indicate that core areas are an essential requirement for individuals and resources they contain cannot be shared with congeners.

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