The Ecology and Conservation of the Spotted-tailed Quoll (Dasyurus maculatus) in a Fragmented Landscape within the Hunter Valley Region of Australia

Abstract

<p>Human-induced habitat loss and fragmentation are leading causes of biodiversity decline around the world. Native mammalian predators can be particularly susceptible to habitat fragmentation due to their relatively large activity ranges and low population densities. Australia possesses a unique diversity of marsupial predators that have suffered major declines in the last 250 years due to significant habitat loss and concurrent impacts from widespread invasive predators.</p> <p>The endangered spotted-tailed quoll (<i>Dasyurus maculatus</i>) is the largest extant marsupial predator on mainland Australia. It is generally considered a forest-dependent species associated with structurally complex contiguous forest. Recent studies on the island state of Tasmania suggest that spotted-tailed quolls occupy a broad niche that includes fragmented agricultural landscapes, likely due to the absence of invasive foxes (<i>Vulpes vulpes</i>). In contrast, quolls on mainland Australia are predominantly restricted to a realised niche of heavily forested habitats, presumed to be because of the threats posed by foxes in fragmented habitats. However, quoll research on mainland Australia has primarily been conducted in intact forest habitats, so their observed forest-dependency might reflect sampling bias rather than preferred habitat. </p> <p>The ecology of quolls in fragmented landscapes on mainland Australia is poorly understood. In the Hunter Valley lowlands of New South Wales, quolls have frequently been detected in habitats fragmented by mining and agriculture. In my research for this thesis, I aimed to investigate quoll ecology in this fragmented landscape. Specifically, I used camera traps to determine quoll density, assess habitat use and investigate interactions with sympatric foxes. Additionally, I used DNA obtained from live-trapped quolls to explore genetic structure and connectivity.</p> <p>Using spatial capture-recapture analyses, I compared quoll densities between a fragmented site and a nearby intact forested site. I was able to identify 173 individual quolls across both sites, and determined that quoll densities were similar between the two sites, indicating the potential importance of forest fragments for supporting quoll populations.</p> <p>I additionally investigated quoll habitat use in the fragmented site by comparing quoll activity and occupancy between four broad vegetation types. I determined that quoll habitat use was flexible, though there was a strong preference for grassy woodlands and dry sclerophyll forests. This important habitat should be retained and protected to benefit quolls living in fragmented landscapes.</p> <p>I further compared spatial and temporal activity between sympatric quolls and foxes to determine if co-existence was facilitated by a separation of activity. In fact, there was considerable spatial and temporal overlap between quolls and foxes, with no evidence that fox presence influenced the activity of quolls. However, the low number fox detections during the study suggests the species' spatial and temporal sympatry could have been facilitated by low fox density</p> <p>I used population structure analysis and pairwise relatedness to compare genetic diversity within and between the fragmented and intact sites, and to determine if any recent movements had occurred between the two sites. From 64 individual quoll DNA samples, I found that the genetic variation for quolls within the fragmented site was comparable to quolls in the intact site. While the two sites were closely related, there was little evidence of recent direct movement between two sites, suggesting they are likely functioning as separate subpopulations within a larger metapopulation.</p> <p>The findings from this thesis reveal important information about spotted-tailed quolls that can benefit their conservation in fragmented landscapes. The fragmented site in this study could be interpreted similar to Tasmania, with low fox occurrence resulting in an expanded realised niche for mainland quolls, compared to their presumed dependency on contiguous forest. The persistence of quolls within this fragmented site in the Hunter Valley also highlights the importance of forest fragments for the overall survival of quolls on mainland Australia. Future research should continue to investigate quolls outside of protected forested landscapes, to expand on our knowledge of this endangered species throughout their range.</p>