The golden-haired sedge-skipper butterfly has been lost from Adelaide’s coastlines and wetlands. Find out how our learnings about a particular rare plant is helping to bring this butterfly back to our urban areas.
The golden-haired sedge-skipper butterfly is considered extinct in the Adelaide area.
It is thought that a missing plant from its usual coastal and wetland environment is a contributing factor to its disappearance. Coastal saw-sedge (Gahnia trifida) is a key plant that provides habitat for this butterfly. Difficulties in collecting viable seed for this plant has meant bad news for the golden-haired sedge-skipper!
Discover how we are working with the South Australian Seed Conservation Centre to learn about this rare grassy plant – and in turn, help bring the golden-haired sedge skipper back to Adelaide.
What is a golden-haired sedge-skipper?
The golden-haired sedge-skipper (Hesperilla chrysotricha cyclospila) is considered extinct around Adelaide but would have made its home in open wetland areas, coastal locations, or even damp forests.
Its wings have a greyish colour around the outside, are mostly brown across the surface, and tend to have orange or golden patches in the centre of each wing. The underside of the wings are most often pale brown, but can be red or grey.
Urban development has contributed to a loss of habitat for this butterfly, which relies on certain coastal and wetland plants for shelter and food.
Why does this butterfly need coastal saw-sedge plants?
Before the golden-haired sedge-skipper becomes a butterfly, its caterpillars find food and shelter within the dense leaves of saw-sedges – particularly the coastal saw-sedge (Ghania trifida).
As well as the caterpillar eating the leaves of this plant, the pupae (cocoon stage) is formed via the leaves of coastal saw-sedge being wrapped together with silk. This is where the caterpillar will transform into a butterfly, usually between October and December.
The coastal saw-sedge doesn’t just provide benefits to this particular butterfly, it’s also a great generalist at attracting a whole range of native butterfly species and provides good habitat for lizards and birds.
What was the problem?
Even though we knew the golden-haired sedge-skipper butterfly needed the coastal saw-sedge plant, not enough was known about how to collect the seeds of this plant and the best way to get these seeds to grow.
In addition to difficulties just obtaining seeds, it was found that they go through a dormancy period – aka, an inactive period – where the seed won’t actually start growing into a plant.
These challenges were limiting the recovery of this important plant, and impacting the recovery of this butterfly across the Adelaide area.
What are we doing to help?
We partnered with the South Australian Seed Conservation Centre to undertake research on the coastal saw-sedge plant.
This research investigated the best time to collect viable seed and determine the ideal germination protocol – that is, the right method to wake these seeds up from their deep sleep.
Already, the work with our friends at the SA Seed Conservation Centre has revealed that the best seeds can be collected during summer months.
And, after lots of experimentation, we also found that using heat shock helps to break down a protective outer coat on the seeds, resulting in a greater amount of germination (aka seeds growing).
Wondering how we apply this heat shock? We literally roast the seeds! They’re popped into an oven for a short period of time to help break down their outer coat. This is not uncommon for a variety of our native plants, and simulates an event such as a natural bushfire.
Using heat shock, combined with maintaining warm conditions while it is growing, is proving to be a good method to get a greater number of these plants to grow.
What do we do with this knowledge?
Now that we have learnt a lot about coastal saw-sedge seed collection and germination requirements, we are sharing that knowledge so more of these rare plants can be grown.
We have shared the best methods for success with commercial and community nurseries. Thanks to the support of these nurseries, thousands of coastal saw-sedge plants have now been grown.
The success means we’re now using these valuable seedlings in a range of restoration projects to get this plant back into the Adelaide area – including on some of our biggest project sites like Field River, Breakout Creek / Purruna Pari, and other areas along the River Torrens / Karrawirra Pari.
Monitoring the survivorship of these plants will form a critical part of the restoration project, and we’re also keeping our eye out for the golden-haired sedge-skipper butterfly to see if it will be able to naturally return and re-establish in Adelaide area.
Learn more about some of Adelaide’s lesser known butterflies, or what else we are doing to help rare plants.