- Title
- The conservation ecology of the toarrana in the Barrington Tops national park, Australia
- Creator
- Alley, Charlotte Eloise
- Relation
- University of Newcastle Research Higher Degree Thesis
- Resource Type
- thesis
- Date
- 2023
- Description
- Research Doctorate - Doctor of Philosophy (PhD)
- Description
- Although native Australian rodents generally have a higher risk of extinction than other native mammals, they are also researched less frequently. In this thesis, I expand our current understanding of one such native rodent: the toarrana (Mastacomys fuscus), which is the only extant member of the Mastacomys genus that has a patchy distribution along eastern Australia between the Barrington Tops National Park (henceforth referred to as Barrington) and Tasmania. Major threats to this species include invasive species and climate change. The northernmost population in Barrington was only discovered in 1985 and exists as a naturally occurring metapopulation. Even though the Barrington toarrana is endangered it has not been researched as much as other populations. Through four chapters, I aimed to assess the status of the Barrington toarrana metapopulation as well as the impact of two major threats to the species – feral horses and climate change. While this thesis was originally designed as a heavily field-based project, the arrival of COVID19 and heavy rains during three years of La Nina meant I pivoted to a more modelling based study. First, I employed species distribution models (SDMs) to establish the impact of various climate and land cover variables on toarrana habitat suitability. With this static SDM (Chapter 1), I reaffirmed the importance of cold temperatures and high precipitation for the toarrana. I then used these models to predict toarrana habitat suitability throughout its entire range, in the Snowy Mountains and in Tasmania. These predictions allowed me to identify locations that should be prioritised for the species’ conservation. I additionally used a dynamic SDM (Chapter 2) to specifically study the toarrana in Barrington. This model demonstrated the importance of swamp habitat and swamp connectivity to this population. Moreover, this dynamic model showed that the Barrington toarrana responds rapidly (< 3 months) to changes in vegetation. With the temporal predictions of habitat suitability obtained by this model, I identified potential refuge patches for the Barrington metapopulation. I also analysed data from the long-term monitoring of the Barrington toarrana (Chapter 3) to describe patterns of population change over time using a range of outcome variables and to identify different climate correlates. I found inconsistent evidence of both temporal change in the population and the drivers of this. The long-term monitoring program relied heavily on unverified indices, meaning they did not account for imperfect detection. Given this and several other potential methodological issues, I make recommendations about the future monitoring of the Barrington toarrana population. The urgency of this cannot be understated given the infrequency with which toarrana have been trapped in recent years despite considerable effort. Finally, with the use of experimental horse exclusion fences that were constructed following the 2019/2020 fires, I examined the impact of horses and fire on vegetation structure and toarrana occupancy in Barrington. I employed a Before-After Control-Impact study design with vegetation and scat surveys to compare horse exclusion areas along with adjacent control areas. Vegetation structure changed rapidly following horse exclusion, with an increase in vegetation height and the proportion of vegetation ground cover, but there were no discernable changes to toarrana occupancy. This was likely due to the short length of horse exclusion (20 months), which was primarily caused by extensive damage to the fences throughout the study period. I also found that fire had no impact on vegetation structure or toarrana occupancy. Based on the challenges I encountered with maintaining fences and monitoring the unexpected habitat disturbance of fire, I make a series of recommendations for future research and management. With these four chapters, I address the knowledge disparity between the Barrington toarrana and other populations. Whilst there is still a need for considerable research and management to ensure the persistence of the toarrana, the conclusions of this thesis can inform this future research and management. Specifically, I made considerable progress towards ensuring that there is sufficient data to accurately determine the conservation status of the Barrington toarrana. Moreover, I provide an insight into the combined threats of feral horses and climate change that can assist in the future mitigation of these threats.
- Subject
- rodent; invasive species; climate change; species distribution model; exclusion fences; Barrington Tops National Park; Mastacomys fuscus; occupancy model
- Identifier
- http://hdl.handle.net/1959.13/1493005
- Identifier
- uon:53462
- Rights
- Copyright 2023 Charlotte Eloise Alley
- Language
- eng
- Full Text
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| Thumbnail | File | Description | Size | Format | |||
|---|---|---|---|---|---|---|---|
| View Details Download | ATTACHMENT01 | Thesis | 18 MB | Adobe Acrobat PDF | View Details Download | ||
| View Details Download | ATTACHMENT02 | Abstract | 265 KB | Adobe Acrobat PDF | View Details Download |