Hairtubing, a technique for detecting mammals, was used to census arboreal marsupials at 70 sites in the timber production montane ash forests of the central highlands of Victoria, south-eastern Australia. Of these sites, 41 were located in linear strips or wildlife corridors and the remaining 29 were in stands of contiguous montane ash forest. Four species of arboreal marsupials were detected in the hairtubing surveys but only one, the mountain brushtail possum Trichosurus caninus Ogilby, was recorded in sufficient numbers to allow subsequent analysis. Data derived for T. caninus from hairtubing studies were compared with those from earlier surveys where stagwatching was used to determine the presence and abundance of the species in retained linear strips. T. caninus was found to be absent from many retained strips during stagwatching surveys but was subsequently detected by hairtubing. Movement by animals into retained linear strips from surrounding areas of contiguous forest, probably whilst foraging, was the most logical explanation for this result. Statistical analyses revealed that T. caninus was most likely to move into strips that supported few trees with hollows and thus areas of poor habitat suitability where there were few resident animals. Such forays may represent an adoption of a retained area as part of an animal's home range. These findings suggest possible functional differences in the use of retained linear strips by T. caninus where some sites provide habitat for resident animals and others, of poorer habitat quality, are used by individuals that do not live in the strip. Within the survey sites, T. caninus was most likely to be detected by hairtubing in those plots where there were numerous tree ferns, Dicksonia antarctica and Cyathea australis, and where the trees Acacia dealbata and A. melanoxylon were present. Thus, some microhabitat features may influence the patterns of use by T. caninus within areas of retained forest. The implications of our results for wildlife conservation in timber production montane ash forests are discussed.