ILWS - Charles Sturt University
ILWS - Charles Sturt University

Phase 2: Ecological assessment of the status of the Southern Bell Frog and Sloane's froglet in Mywurlie station, One Tree, NSW (2018-2019)

Researchers/Investigators

Associate Professor Skye Wassens, Dr Alexandra Knight, Dr Geoff Heard, Dena Paris  & Dr Amelia Walcott

Funding

Murrumbidgee Irrigation Ltd., $45, 673

Research Theme(s)

Environmental Water and Biodiversity Conservation

Description

This project built on previous surveys done in 2017 for the original project that’s aim was to establish whether or not there were populations of Southern bell frogs and Sloane’s froglet on a large dryland grazing property in the Wah Wah district, an arid zone within the Murrumbidgee Irrigation Area.

Southern bell frogs are listed as endangered in NSW, and vulnerable nationally. Sloane’s froglets, formerly listed as vulnerable in NSW, were recognised in 2019 as a national endangered species.

Currently, the district receives its stock and domestic water through open channels. However Murrumbidgee Irrigation, with funding from the Federal Government, is changing that with water to be delivered by pipes. Some of the landholders in the district were concerned that this could impact on the two frog species.

This project involved two repeat surveys of potential habitats along channels scheduled to be decommissioned to establish the extent of the Southern bell frog populations within the impact zone, and establish the importance of impacted populations in the context of broader populations in the region.

Field surveys were conducted in October and December 2018 to coincide with water flows down the channels and into connected stock dams. In total, 48 sites were surveyed across the Wah Wah area and adjacent regions, covering 17 sites along the channels, 28 feeder dams, and three points in Barren Box swamp. The surveys specifically sought to:

  • establish the extent and significance of Southern Bell Frog and Sloane's Froglet populations that will be, or are likely to be, impacted by altered hydrological regimes due to channel decommissioning in the Wah Wah area
  • identify potential mitigation options to offset potential impacts of the channel decommissioning process

The researchers detected seven species of frogs, with the Spotted Marsh Frog, the most prevalent.  No Sloane's Froglets were detected, in accord with results from previous surveys in 2017 at Mywurlie Station, and Southern Bell frogs were only detected at one of three sites at Mywurlie at which they were detected in 2017. They were not detected elsewhere in the study area.

In their final report, the researchers recommended that in respect to Sloane's Froglet significant populations were unlikely to be found in the Wah Wah area; and a significant impact on an important population of this species from channel decommissioning in the Wah Wah area was unlikely.

With regards to Southern Bell Frogs, surveys completed throughout the study area in the spring and summer of 2018 failed to provide further detections of Southern Bell Frogs outside of Mywurlie Station. Resurveys at Mywurlie were also suggestive of reduced activity or abundance during the 2018 breeding season, with only one individual detected

The researchers speculated that this population may be an ephemeral, range-edge expansion facilitated by the extensive flooding during the 2016/2017 breeding season. Extensive, flood-assisted dispersal and colonisation events have been documented for this species within the Lowbidgee region. The researchers recommended that the Mywurlie population of the Southern Bell Frog was unlikely to meet the criteria of an ‘important population’ under the EPBC Act. 2, and, if so, decommissioning of channels within the Wah Wah area would not have a significant impact on an important population.

However, they highlighted that the Mywurlie population was wholly reliant on channel flows for persistence, in which case offsetting or mitigation activities should be pursued to mitigate the impact of channel decommissioning upon the population.  

Mitigation options focussed on the persistence of the Mywurlie population could also focus on securing and enhancing available habitat. This could include:

  • Establishing permanent water at existing known sites, and/or neighbouring sites
  • Bolstering habitat quality by stock exclusion fencing and/or aquatic revegetation
  • Removing exotic fish from existing habitat (particularly European Carp and Mosquito Fish) to limit egg and tadpole predation

Outputs

Knight, A., Heard, G., Wasserns, S., Paris, D. (2018) Ecological assessment of the status of the Southern bell frog and Sloane's Froglet in part of Wah Wah area within the Murrumbidgee Irrigation Area: Final report to Murrumbidgee Irrigation Ltd.

Contact

Dr Alexandra Knight email

Port Macquarie campus

February 2020