Office for Environmental Programs - Theses

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    Persistence of the Eastern Dwarf Tree Frog (Litoria fallax) in Melbourne: habitat characteristics and climatic niche
    Bevelander, Jane ( 2014)
    Human activities are increasingly leading to the movement of species into areas outside their natural range. The Eastern Dwarf Tree Frog (Litoria fallax) has been translocated from its original range in Queensland and New South Wales, Australia to the city of Melbourne, 600 km south of its previous range. Individuals of this species are known to travel on transportation trucks in fresh food and agricultural produce, and they are known as a 'banana box frogs' for their penchant for hiding in banana boxes. Litoria fallax has now been recorded at 28 sites around greater Melbourne and is known to be persisting at 7; however, with many gaps in the wildlife databases, this figure is likely to be higher. With Local habitat features known to significantly influence the presence of frog populations I conducted habitat surveys at sites throughout Melbourne where L. fallax is known to have and have not persisted. Its ongoing presence at a site was most closely correlated with a higher cover of submerged and riparian vegetation. With L. fallax being so far to the south of its original range, climate was an important factor to explore, so I ran a climate-suitability model for L. fallax using the software package Maxent. The model included five climatic variables-temperature seasonality, minimum temperature of the coldest quarter, mean temperature of warmest quarter, precipitation of warmest quarter and minimum relative humidity-chosen for their relevance to the biology and behaviour of L. fallax, such as the association between breeding and rainfall events. Results of the modelling showed that not only does Melbourne fall within the suitable climatic range of L. fallax, but that this range extends along most of the east and south coast of Australia. This suggests that a substantial range expansion of this species is possible. Whilst greater Melbourne does fall within the climatic niche of L. fallax, the predicted climate suitability varies throughout the region with a lower relative probability of occurrence in the northern suburbs where most of the populations are persisting. Thus, my research demonstrates that climate modelling alone is not sufficient to assess the potential niche of an invasive species
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    Habitat preference and distribution of the Powerful Owl (Ninox strenua) on the Mornington Peninsula, Victoria
    Parkins, Kate Anna ( 2013)
    Identifying the distribution of threatened fauna is fundamental to allocating scant resources for conservation purposes. Predictive habitat modelling based on environmental data from species records is currently used to inform conservation management but research is needed to verify the reliability of those Species Distribution Models (SDMs). This study focused on the threatened Powerful Owl Ninox strenua, in a region that lacked historical records but where SDMs predicted suitable habitat was available. This study was aimed at ground truthing the existing habitat suitability model for the Powerful Owl while providing new data to improve the spatial comprehensiveness of the model. The Victorian state-wide habitat suitability model for the Powerful Owl was used to stratify the study area (Momington Peninsula) into three classifications of habitat suitability (Low, Low- Medium and Medium). Forty sites were randomly selected comprising 13 low suitability, 13 low-medium habitat suitability, and 14 medium habitat suitability sites. Powerful Owl call-playback was undertaken a total of 112 times with each site surveyed at least once. A subset of 6 sites per habitat suitability class were surveyed 5 times to provide an estimate of detection probability. Repeat surveys at the same site were important to improve the probability of determining if Powerful Owls were present at a site (one to four visits increased overall detection from 33 per cent to 80 per cent). A Bayesian state-space modelling approach was used to estimate the occupancy of Powerful Owls as a function of habitat suitability class and prey abundance. Detectability was modelled using survey conditions (wind speed). This study shows that existing state-wide models of Powerful Owl habitat suitability reliably predict the occupancy of this species on the Momington Peninsula. Powerful Owls were found at a higher proportion of Medium (72%) and Low-Medium sites (66%), with lower levels of occupancy in Low habitat suitability sites (24%). This study provides new information regarding the distribution and habitat preference of the Powerful Owl on the Momington Peninsula, while highlighting the value of predictive species distribution modelling for wildlife conservation and management
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    Assessment of threats to the Mekong River Irrawaddy dolphin (Orcaella brevirostris)
    Ryan, Gerard Edward ( 2010)
    The Mekong dolphin is a highly threatened freshwater population of Irrawaddy dolphin, Orcaella brevirostris, inhabiting the Mekong River in the Lao People's Democratic Republic and Cambodia. Despite the Mekong dolphin's low population size and rapid decline, there has thus far been no rigourous investigation of threats to the population, a gap this risk assessment aims to fill. A wide variety of threats are discussed including small population issues, boat traffic, fishing, tourism, environmental contamination, hydropower development and disease. Dolphin bycatch and disease are found to be the greatest threats, but competing mutually exclusive hypotheses prevent any definitive conclusions being drawn. It is imperative that this dichotomy be addressed as soon as possible and appropriate action taken to eliminate the threat. The development of hydropower dams, particularly on the mainstream of the Mekong River within dolphin habitat loom as the greatest future threat that may spell the end for this beleaguered dolphin population. Further indepth stochastic modelling is recommended to better understand the interactions and implications of some threats and guide conservation management of the population
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    Effects of experimental flooding on egg survival of Krefft's River Turtle: implications for freshwater turtle conservation
    Hollier, Claire ( 2012)
    Anthropogenic changes to river catchments via changes to flow rate and volume can dramatically influence biodiversity. Most of Australia's major rivers are now impounded from the construction of dams and weirs causing the loss and significant alteration to habitat due to modified flow regimes. Such changes can negatively impact biodiversity, particularly specialist species. For example, anthropogenically altered flow regimes expose freshwater turtle to a seasonal inundation events that are assumed to exacerbate egg mortality during the incubation phase. Thus flooding of freshwater turtle eggs has been identified as an additional threatening process that could further impact both listed and non-listed freshwater turtles. Consequently, understanding the degree of mortality imposed on turtle eggs during incubation is a crucial step to ascertaining management implications from altered flow regimes on turtle populations. Here I conducted experiments to specifically identify the effects of 1) duration and 2) timing of inundation on Emydura macquarii krefftii egg hatching success and hatchling phenotypes. This was done in order to measure both direct and potentially indirect mortality costs associated with altered river flow regimes. Four treatments of eggs; control, 30 minutes submersion, one hour submersion and 6 hours submersion were flooded at nine periods during incubation (within the first 24 hours then every week following). Analysis revealed that inundation for any length of time caused a significant increase in egg mortality compared to control eggs. The developmental age at which inundation treatments were applied also had a significant impact on hatching success, with age 0 exhibiting the highest mortality rate and other developmental ages displaying fairly similar but increased mortality relative to controls. These results suggest that E. m. krefftii eggs are very sensitive to even brief episodes of inundation, especially within the first 24 hours of incubation. Moreover, if other turtle species are proven to exhibit similar sensitivities to inundation during egg incubation from altered river flow regimes these results suggests additional and potentially high mortality to all terrestrial nesting freshwater turtles. Ultimately these results support the need to prioritise informed management of anthropogenically altered flow regimes in order to prevent potential loss of an entire guild of vertebrates and their ensuing ecological function
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    Nature relatedness, dispositional empathy with nature and pro-conservation behaviours among young Vietnamese urban residents: applying conservation psychology approach for human dimensions of wildlife conservation and management in Vietnam
    Tien Du, Le Thuy ( 2013)
    Conservation psychology aims to bridge the gap between psychological researches on human behaviours and practical environmental issues. In Vietnam, wildlife is in state of crisis. The bourgeoning demands of wild animal products from increasing prosperous urban residents in Vietnam have contributed to the over exploitation of wild species. Applying the theories and methods from conservation psychology, particularly nature relatedness and dispositional empathy with nature, a web survey was conducted to measure the motivations of the young Vietnamese urban residents in Hanoi and Danang cities. The findings lent support to studies showing a relationship among nature relatedness, dispositional empathy with nature and pro-conservation behaviours. A mediating mechanism of dispositional empathy with nature in the relationship between nature relatedness and pro-conservation behaviours were supported. In addition, the association between self-efficacy and pro conservation behaviours was also found. The study provided important implications for conservation practitioners in using empathy - arousal appeal, efficacy-enhancing information, and normative messages for engaging the young people in wildlife conservation activities. For long-term positive effect, designing environmental education for building connection to nature and empathy with nature as enduring traits will be preferred. Finally, for human dimensions of wildlife conservation and management professionals in Vietnam, implications about insights regarding the visions of the urban biodiversity and the positive and negative effects on human and natural well-beings were discussed
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