Golden Sun Moth (Synemon plana)
The Golden Sun Moth (Synemon plana) was declared an endangered species in the ACT in 1996 and has special protection status. It is listed as critically endangered nationally, endangered in NSW and threatened in Victoria.
The species was once widespread in south-eastern Australia and closely linked with temperate grasslands dominated by wallaby grasses. Approximately 99.5% of Natural Temperate Grassland in Australia has been destroyed or drastically altered since European settlement. Remnants are degraded by stock grazing and weed invasion. Today Golden Sun Moths can be found in remnant patches of temperate grassland, and also some open woodlands with a grassy understory and some grassy woodlands that have been cleared of trees.
The known area of occupied habitat is 150 km². Currently, the species is known from 100 sites in Victoria, 48 in NSW and 78 in the ACT. In the ACT the species occurs in lowland areas next to Canberra and in small sites within the city that range from 0.06 hectares to more than 300 hectares.
The Golden Sun Moth is a medium-sized moth with clubbed antennae and no functional mouthparts. Males and females have different colouring and patterns on their wings. The adult moths live only a few days. Males fly low and rapidly over the grassland during the late morning and early afternoon, searching for females basking in inter-tussock spaces or perched on grass tussocks and exposing their golden hindwings when a male flies overhead. Males are unlikely to fly more than 100 metres from suitable habitat, and females hardly at all, so populations separated by 200 metres or more are likely to be isolated.
After mating, the females move from tussock to tussock, laying 2 millimetre-long eggs into their bases. The larvae develop underground, where they feed on the roots of a few species of grasses.
Habitat requirements for the moth are generally consistent with the requirements of other threatened grassland fauna including the Grassland Earless Dragon and the Perunga Grasshopper, which often co-occur with the moth.
A high proportion of grassy ecosystems have been cleared for agriculture and urban development, and most of the remnants are fragmented and degraded. Of the estimated 1800 hectares of Golden Sun Moth habitat remaining in the ACT, 22% has been approved or proposed for urban development, 23% is on Commonwealth land with an uncertain future, and 45% is in existing or proposed nature reserves or existing/proposed EBPC offset areas.
- further loss, fragmentation and degradation of habitat
- weed invasion that fills in the inter-tussock spaces and reduces the density of grasses that moth larvae eat
- wildfire or inappropriate fire regimes
- extremes of herbage mass —either too much or not enough
- cultivation and pasture improvement
- herbicides, pesticides and excess nutrients from fertilisers
- altered drainage.
The predicted changes in climate in the next 50 years are likely to see the ACT become warmer and drier, with increases in extreme weather events and bushfire risk. The direct effects on the Golden Sun Moth are not known. However, plants advantaged by climate change are likely to include grasses that are not thought to be Golden Sun Moth larval food plants, some weed species and woody species that may invade grasslands.
Almost 60% of known Golden Sun Moth habitat in the ACT is under conservation management. Most important sites are either in nature reserves or under ACT Government management as offsets under the Australian Government Environment Protection and Biodiversity Conservation Act. Many of these sites are also subject to long-term monitoring to ensure the protection of key populations.
Through the Golden Sun Moth Action Plan (2017), which continues the 2006 action plan, and the ACT Native Grassland Conservation Strategy (2017), the ACT Government proposes to maintain the conditions, in the long term, that encourage a viable, wild population as a component of the indigenous biological resources of the ACT and as a contribution to regional and national conservation of the species.
Specific objectives of the action plan are:
- Conserve habitat, particularly through mowing or grazing and removal of weeds and potentially through patch burning.
- Provide offset areas, with management plans, for areas subject to urban development.
- Ongoing research and monitoring.
- Enhance the long-term viability of populations through management of adjacent grassland to increase habitat area and connect populations.
- Collaborate with research institutions and non-government organisations and encourage citizen science and volunteers.
Larger populations (500 or more adults) on larger sites (50 hectares or more) have highest priority for protection, as they have the greatest chance of long-term viability. Medium-sized populations have the potential to be viable over the longer term if habitat quality is maintained though appropriate management. Small populations at sites that contribute to research or public education (e.g. York Park in Barton) are also a priority for protection.
Where the species occurs on Commonwealth land, the ACT Government will continue to liaise with the Australian Government and Canberra Airport to encourage continued protection and management.
Glasshouse and field trials have indicated that Golden Sun Moth larvae can be translocated either individually or in soil containing larvae directly from a development area to translocation sites. Long-term survival of populations in a new location is still being assessed by ongoing monitoring.
For an improved understanding of the species’ ecology, habitat, propagation and translocation, the ACT Government will continue to collaborate with other states, universities, CSIRO, Australian National Botanic Gardens, other research institutions and non-government organisations.
- Golden Sun Moth Action Plan, 2017
- The ACT Native Grassland Conservation Strategy and Action Plans, 2017
- See the moth’s distribution at the ACTmapi website.
- Australian Government’s Conservation Advice