School of Agriculture, Food and Ecosystem Sciences - Theses
Permanent URI for this collection
Search Results
1 - 1 of 1
-
ItemImpacts of urbanisation on autumn-breeding amphibians in the greater Melbourne region( 2016-06-17)Modification of environments by urban development is a significant threat to global amphibian populations. Of all vertebrate classes, amphibians are facing the greatest risk of extinction – with 25% of species in Australia threatened with extinction. Urbanisation can result in habitat loss and degradation, changes to water availability, and introduction of exotic competitors and predators, which all have the potential to impact on amphibian populations. Past studies have focused on the effects of urbanisation on aquatic breeding amphibian species, but few have investigated how terrestrial breeding species may be responding to these threats considering they depend on habitat availability for reproduction. In the rapidly expanding urban centre of Melbourne, Australia, there are three terrestrial breeding species that call throughout the autumn months, the Victorian smooth froglet (Geocrinia victoriana), the southern toadlet (Pseudophryne semimarmorata), and Bibron’s toadlet (Pseudophryne bibronii). This project investigated how G. victoriana and two associated frog species, the common eastern froglet (Crinia signifera) and the southern brown tree frog (Litoria ewingii), are responding to urbanisation in the greater Melbourne region. To investigate this question I visited 45 water bodies in the greater Melbourne region in the Austral autumn. At each site I completed visual and acoustic amphibian surveys, vegetation surveys for terrestrial and aquatic vegetation cover, and recorded abiotic measurements. The level of urbanisation at each site was represented by the ratio of total area within a surrounding sub-catchment covered by impervious surfaces. I utilised Bayesian regression modelling to estimate the effect of variables such as impervious surface cover and aquatic vegetation cover on the probability of detecting G. victoriana, C. signifera, and L. ewingii. The results revealed a strong negative association between impervious surface cover and the probability of detecting G. victoriana, although, there was less evidence to suggest the same relationship for C. signifera or L. ewingii. Environmental factors such as aquatic vegetation cover had a positive effect on the probability of occurrence of G. victoriana and C. signifera, however, this was not found for L. ewingii. The data presented in this study support the conclusion that G. victoriana is vulnerable to urban development, whereas C. signifera and L. ewingii may be better suited for adapting to these novel environments. However, this study was unable to identify the direct links between urbanisation and the persistence of terrestrial breeding species such as G. victoriana, and this should be experimentally examined in future research. The findings presented in this research have important management implications for all amphibians in the greater Melbourne region, and highlights the need to encourage a variety of different habitat types and their persistence in an urban context.