Spatial ecology of Litoria raniformis within modified Tasmanian landscapes.
Tim Garvey
Abstract:
Within Tasmania, Australia, the vulnerable growling grass frog (Litoria raniformis) has experienced a rapid contraction in its distribution. This reduction is primarily attributed to loss of habitat through landscape modification and improved drainage of agricultural lands. The loss of seasonal flood water has placed increased importance on permanent water-bodies. Tasmanian agricultural and commercial forestry landscapes often feature small artificial ponds, utilized for watering livestock and fighting wildfires. An improved knowledge of how L. raniformis may be utilizing anthropogenic ponds is required for improved conservation management. We implemented telemetric tracking in order to evaluate the spatial ecology of L. raniformis (n = 20) within agricultural and managed forestry sites; with tracking conducted periodically over the breeding season (November/December, January/February, March/April). We investigated (1) potential differences in habitat utilization between agricultural and plantation sites and (2) the distances travelled and post-breeding dispersal of individual frogs. Frogs were found to remain in close proximity to the original point of their collection throughout November/December, moving away from these natal ponds by January/February. Individuals traversed exposed plantation understory and agricultural pasture in order to enter patches of native scrubland. By the final tracking season all individuals had retreated to scrub corridors. No difference was found between sexes across the three tracking periods with regards to pattern of movement. Rising seasonal temperatures coincided with an increased movement by individuals towards native scrub refugia. The patterns of movement reported in this investigation emphasize the importance of manmade water-bodies within modified landscapes towards the conservation of L. raniformis. The use of natural scrubland as cyclical retreats between breeding seasons also highlights the importance of the continued preservation of remnant vegetation. Loss of artificial dams or remnant scrubland in heavily altered landscapes could see the breakdown of the
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