Year

1988

Degree Name

Master of Science (Hons.)

Department

Department of Biology

Abstract

Decreases in area of natural vegetation have occurred increasingly since European occupation of Australia. Many remaining large tracts are being dissected by roads, railway lines and strips of development. These are serious problems for attempts at conservation of the native biota. Large animals are likely to be the most conspicuously affected. This study examines conservation of the mammal fauna in the Illawarra region of New South Wales in the context of the remaining patches of native vegetation.

The "Region" is defined as the area bounded by the Sydney urban area in the north, the line of the western edge of the Water Board catchments in the west, the Shoalhaven River in the south and the ocean in the east. Within this region, natural vegetation remains mostly as three large tracts of land in the escarpment/tablelands (Royal National Park, Water Board catchments, and Morton National Park and surrounds) and numerous isolated patches, mostly on the coastal plain. A unique feature of the region, especially in the northern end, is the close proximity of highly developed commercial and urban areas to the large tracts of native vegetation contained within the various reserves. Ten study sites were established in the large tracts and 23 were established in the isolated patches.

The terrestrial mammal fauna of each study site was surveyed between 1983 and 1987, using a variety of techniques such as trapping, spotlighting and identifying tracks, scats and other signs. Historical records of mammal occurrences were obtained from a variety of sources; personal interviews with long-time residents, archival material from early settlers and explorers and museum records. A detailed description of the mammal fauna of the region as a whole, and of the specific study sites is presented, related to the vegetation, geology, topography etc.

These surveys show that the region as a whole contains a wide diversity of mammal species (49 species including bats; 32 species of terrestrial mammals). This is almost the full complement expected on the basis of historical records (33 terrestrial species). Thirteen introduced species were recorded. Much of the current diversity is contained within the large tracts of reserved vegetation in the escarpment/plateau areas. Individual isolates contained only from 0 to 13 species of native, terrestrial mammals. Low species diversity of these isolates was related mainly to three factors: area, degree of isolation and degree of disturbance.

I argue that the large tracts of relatively undisturbed vegetation of the escarpment and plateau are an essential element in future mammal conservation in the region, although small isolated fragments, especially those containing unusual vegetation types, will be of some value. The close proximity of development to these tracts of vegetation means that disturbance will be a continuing pressure. The analysis of the isolates sampled showed the importance of large size and close proximity to other native vegetation in sustaining a high species diversity. These principles should be applied to future design and management of the escarpment reserves. I identify certain areas of land which should be added to existing reserves to ensure the preservation of specific habitats and hence certain mammal species. I argue that the isolating impact of roads and railway lines must be overcome, and I also indentify "wildlife corridors" to reduce the effects of fragmentation of this formerly continuous tract of vegetation.

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