The use of corridors by mammals in fragmented Australian eucalypt forests
Downes, SJ, Handasyde, KA & Elgar, MA 1997, Conservation Biology, vol. 11, no. 3, pp. 718-726.
The composition and density of mammalian assemblages utilising forest patches, corridors and pasture in fragmented forest landscapes vary between species, generally depending on individual species characteristics. This study highlights the importance of corridors, particularly for arboreal mammal species such as the koala, as they provide resident habitat and functional pathways in a fragmented forest system.
Fieldwork for this study was conducted in the Strathbogie Ranges of north-eastern Victoria, Australia over a period between February and late June in 1994. Fixed transect lines were used to measure the presence and density of native mammal species at six replicate sites in four habitats. These sites varied in terms of the number of patches, corridors, roads, fences and other barriers the transects intersected. The type and number of species were recorded by spotlight, live-trap and daytime observation surveys. Results showed highest recordings of koalas in forested areas; however, the highest density of koalas was recorded within corridors distant from forest patches. The combined data of all species showed densities of mammals recorded within corridors close to forested patches were similar to actual forest recordings with fewer sightings at corridors distant from forests. Despite the corridors furthest away from forests containing the lowest number of species, they also recorded the highest density of species.
This study found that mammals utilise patches, corridors and pasture areas in fragmented landscapes in different ways, primarily due to individual species characteristics and degree of tolerance to interactions with other species. For most species, corridors provide microhabitats between forest patches, while others utilise these areas for travel pathways, potential hunting grounds, shelter or food resources. This study found that some survey data may not be a true representation of the utilisation of such corridors due to the size of the study area. For example, koalas recorded in the corridors were all of adults and considered to be a resident population, as juveniles would be expected to have a less stable home range. A larger study area may take this into consideration as some smaller corridors may not be able to support a resident population of a particular species.
Results obtained by this study highlight the importance of corridors within a fragmented landscape as they provide important habitat for the majority of native mammals in surrounding areas, including local koala populations. It is evident that the use of corridors differs between species, and for koalas these corridors provide valuable habitat sufficient to support resident populations of the species. It is important to conserve and protect these corridors in fragmented forest landscapes as natural remnant vegetation can mitigate the effects of habitat loss and fragmentation by connecting forest patches.
Summarised by Robyn Boldy
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