Hypothesised causes of the observed world-wide decline of amphibian populations are varied and in some cases contentious. Insufficient information relating to the autecology of many amphibian species can cause erroneous speculations regarding critical habitat requirements and hence management programs designed to enhance population viability are often unsuccessful. Most amphibians display a bi-phasic life history that involves occupation of an aquatic breeding habitat and terrestrial habitats that are used for foraging, and shelter from predation and environmental stress. However, the focus of most amphibian research is centred on the breeding habitat, with limited research being conducted into the terrestrial habitat requirements of most amphibian species. Barakula State Forest is a large continuous area of open woodland situated in the semi-arid region of Queensland. The forest supports 21 species of endemic anurans, many of which use ephemeral waterbodies for breeding. This area is, therefore, an ideal location to test the relative importance of terrestrial habitat on the distribution of a suite of frogs that display different morphological and physiological characteristics. On the landscape scale, the attributes of the terrestrial environment at three survey areas within Barakula were similar. However, at the patch scale, ground truthing showed there were considerable variations in vegetation and ground cover attributes within and between each survey site. Measured properties of the soil also tended to vary within and between sites. Soil texture ranged from sandy to heavy clay, soil pH ranged from 3.9 to 6.4 and soil moisture varied considerably. Agar models, used for testing evaporative moisture loss at different microhabitats, retained significantly higher levels of moisture when positioned in the buried microhabitat during summer, but in winter, models that were placed under leaf litter retained higher levels of moisture. Variations in levels of moisture loss at the five different microhabitats were evident within and between the survey sites. Despite a prolonged drought, 1844 native frogs representing 17 species were pitfall trapped. Members from the family Myobatrachidae comprised 94% of these captures, and burrowing species accounted for 75% of total captures. Species were not randomly distributed within or between the survey sites. Vegetation attributes and soil properties played a significant role in influencing the catch rates and traplines that supported similar vegetation and soil attributes also tended to catch similar species. Capture rates of six of the seven burrowing species were significantly influenced by soil properties. When given a choice of four different microhabitats created in enclosures, individuals from five species showed varying responses to habitat choice during night time activity. During daylight all species tended to avoid bare areas and burrowing species tended to burrow under some form of cover. Pseudophryne bibronii metamorphs showed a significant avoidance to soils with high pH. The number of Limnodynastes ornatus metamorphs was significantly and positively correlated with moisture levels surrounding a breeding area. Limnodynastes ornatus metamorphs tended to avoid areas that did not support some form of cover. Embryos from the terrestrial egg laying P. bibronii translocated to sites with varying levels of soil pH, suffered increased mortality where the soil pH was >4.8. In the laboratory, embryonic survival was not significantly different between the four pH treatments. There was a significant influence of fungal infection on survival rates and ranked fungal infection was significantly different between the four pH treatments. The terrestrial environment at the three survey sites has provided sufficient protection from environmental elements to allow a large diversity of anurans to persist for long periods without access to permanent water. Management must consider the importance of the non-breeding habitat when defining buffer zones, restoration programs and conservation strategies to ensure that the complete set of ecological requirements for frog species are provided.
| Identifer | oai:union.ndltd.org:ADTP/265602 |
| Date | January 2008 |
| Creators | Chambers, Joanne |
| Publisher | Queensland University of Technology |
| Source Sets | Australiasian Digital Theses Program |
| Detected Language | English |
| Rights | Copyright Joanne Chambers |
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