Factors influencing the occurrence of mammals in retained linear strips (wildlife corridors) and contiguous stands of montane ash forest in the Central Highlands of Victoria, southeastern Australia

Abstract

Hairtubing was used to census mammals at 70 sites in 53 year old mountain ash ( Eucalyptus regnans) and alpine ash ( Eucalyptus delegatensis) forest in the Central Highlands of Victoria, southeastern Australia. A total of 40 sites was located in linear strips or wildlife corridors that were retained in timber production areas. The remaining 30 sites were in stands where the adjacent forest had not been logged. Thirteen species of mammals were detected in the hairtubing surveys, but only three were detected frequently enough to allow detailed analysis. The detectability of these animals and other less commonly recorded species varied according to the placement and the type of hairtubes that were used. Although data on feral predators were very limited, no apparent effect of the proximity of hairtubing plots to roads was detected. Detailed statistical analyses of the data were conducted at two levels: the site level, and for individual hairtubing plots. Logit regression models were used to explore the relationships between: (1) the probability of detecting brown antechinus ( Antechinus stuartii), bush rat ( Rattus fuscipes) and swamp wallaby ( Wallabia bicolor) and the measured dimensions (e.g. width and length), environmental attributes and vegetation structure of retained linear strips; (2) the probability of occurrence of Antechinus stuartii, Wallabia bicolor and R. fuscipes in hairtubing plots within areas of contiguous forest and retained linear strips and the characteristics of the vegetation structure and plant species composition in a 10 m area surrounding such plots. For the first group of models, the variation in topography within retained linear strips significantly influenced the proportion of detections of Antechinus stuartii and R. fuscipes, although there was a different response for each species. Other significant explanatory attributes in these models included the number of roads and tracks that disrupted vegetation cover as well as structural and floristic parameters such as the dominant tree species on the site and the basal area of Acacia spp. Analyses of the combined data for the two types of sites indicated that Wallabia bicolor was more likely to be detected in plots within E. regnans forest and where there was a limited cover of ferns on the forest floor. The type of study site (retained strip vs. contiguous forest) was a significant variable in the models developed for Antechinus stuartii and R. fuscipes, reflecting a significant influence of the configuration of sites on the probability of detection of these animals. Separate models for the two types of sites were developed both for Antechinus stuartii and R. fuscipes. The dominant species of tree was a significant factor in several of these models, and there were significantly fewer records of Antechinus stuartii from the ends of strips of E. delegatensis forest. Most of the other explanatory variables were measures of the vegetation cover and plant species composition which are likely to reflect the importance of the suitability of foraging substrates for Antechinus stuartii and R. fuscipes. For these species, a different set of variables was found in each of the various models that were developed. These findings imply a degree of partitioning of the use of the forest environment by Antechinus stuartii and R. fuscipes. They also suggest that patterns of microhabitat use by some species of mammals may change when areas of montane ash forest are confined to a linear configuration (i.e. a retained strip).