Office for Environmental Programs - Theses
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ItemPersistence of the Eastern Dwarf Tree Frog (Litoria fallax) in Melbourne: habitat characteristics and climatic niche( 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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ItemHabitat preference and distribution of the Powerful Owl (Ninox strenua) on the Mornington Peninsula, Victoria( 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