Thatching Grass information sheet For the protection of Yellowish Sedge-skipper habitat

on southern Yorke Peninsula

What is Thatching Grass and why is it good?

The Yellowish Sedge-skipper study is part of the Samphire Coast Icon Project, supported by the Adelaide

and Mount Lofty Ranges Natural Resources Management Board through funding from the Australian Government.

Species reintroduction project

Thatching Grass is the common name for Gahnia filum and it’s a relatively

common native sedge (Fig. 1) around the southern Yorke Peninsula. It is a

coastal sedge that commonly grows in mildly saline swamps.

It has many benefits for those who have them on their property:

- It is very low maintenance and long lived.

- It tolerates flooding and drying in fresh to brackish conditions.

- If retained and expanded, a sedgeland can help prevent soil salinisation.

- It hosts native pollinators as well as predators and parasites that kill pests

(e.g. Thrips).

- It provides a habitat for native animals; increasing biodiversity.

- It is part of a major species reintroduction and habitat restoration project

on the northern Adelaide coastal plains.

The Hesperilla flavescens (Yellowish Sedge-skipper - Fig. 2), used to flourish in

the northern Adelaide coastal plains. It has not been seen in the area since 1985

and is believed to be regionally extinct.

It lives in Thatching Grass sedgelands where it spends 12 months as a larva

(caterpillar - Fig. 2) feeding on its leaves. Not only does it eat the leaves, it builds

leaf shelters to protect itself during the day (Fig. 2). Thatching Grass used to be

common in the northern Adelaide coastal plains and we are working to increase

and improve this habitat. There are currently many healthy populations of YSS

in sedgelands across southern Yorke Peninsula.

The Nature Conservation Society of South Australia is working with land holders,

community groups, Natural Resources Adelaide & Mount Lofty Ranges, and

BirdLife Australia to examine the feasibility of reintroducing this species. We are

all working together to keep known butterfly populations and habitats safe,

grow and restore its habitats in the northern Adelaide coastal plains, and

reintroduce the Yellowish Sedge-skipper (YSS) to its historic range.

It is proposed to collect larvae from large, sustainable YSS populations on

southern Yorke Peninsula. These larvae will create founding populations in the

target habitats on the northern Adelaide coastal plains.

Figure 2: Top: a late instar larva of Yellowish Sedge-skipper (YSS). Photo: C. Butcher.

Middle: a shelter made by a YSS larva between the leaves of Thatching Grass. Photo: C. Butcher.

Bottom: a mature female YSS butterfly. Photo: A. Stolarski.

Figure 1: a healthy Thatching Grass tussock.

Photo: C. Butcher.

Areas of interest Thatching Grass sedgelands of interest

on southern Yorke Peninsula are

known to have populations of the

Yellowish Sedge-skipper (Fig. 3).

The large and smaller populations on

southern Yorke Peninsula will act as

sustainable donor populations for the

target habitats on the northern

Adelaide coastal plains.

It is important to keep the sedgelands

in good condition so that the

populations can continue flourishing

and support butterfly reintroduction.

Different types of sedgeland

Sedgelands of interest

Large YSS populations

Target habitats

Translocation of YSS

Thatching Grass is a versatile and resilient plant that can tolerate a wide

range of salinity and a dynamic water cycle. It is often found in low-lying

swamps or wetlands in cracking soil (Fig. 4). They can grow alone but they

are often found with Melaleuca sp. +/- Eucalyptus sp. and low ground

cover.

In wetter settings that may be annually flooded the sedgeland can form a

vast flat ‘carpet’ of almost nothing but Thatching Grass. In settings that are

flooded less frequently, the tussocks are more spaced and produce a less

uniform coverage (Fig. 4).

Although the wetter sites may have bigger populations, both sites can

sustain productive populations. The butterfly needs the sedgeland to have

certain characteristics to make it suitable. The sedgeland must:

- have fresh green growth to feed the larvae. The fresh leaves are more

palatable and flexible enough to build shelters (Fig. 5).

- not be over-crowded (Fig. 6). The YSS need access at the side of the

tussock to lay eggs, as seen in the photos to the right.

- not be shaded by many trees. An open and flat area is ideal.

- not be heavily grazed. This removes the fresh leaves that the YSS prefer

and sometimes the larvae are inadvertently eaten within them.

Figure 4: Examples of Thatching Grass

sedgelands. Top: a small healthy

sedgeland with Melaleuca

halmaturorum. Middle: a large wet

sedgeland near Point Turton. Bottom: a

medium sized drier sedgeland near Long

Swamp. Photos: C. Butcher.

For more information - Email: ncssa@ncssa.asn.au | Phone: 08 7127 4630

Figure 3: Thatching Grass regions with Yellowish Sedge-skipper populations and target habitats for YSS translocation

Figure 5: a YSS shelter (circled) built in

a young Thatching Grass tussock.

Photo: C. Butcher.

Figure 6: Thatching Grass sedgeland

that have been overcrowded by other

plants. Photo: C. Butcher.

Creating a butterfly habitat One of the best way to create a habitat for this butterfly is to have a healthy patch of Thatching Grass tussocks on

low, flat land with a few flowering trees. The Yellowish Sedge-skipper relies on Thatching Grass* to lay its eggs; its

larvae survive on its leaves until it becomes a butterfly. Thatching Grass grow in a variety of soil types and thrive

where fresh to brackish water stands over winter that may dry out in summer (Coleman and Coleman, 2000).

They can be planted 0.5 to 1 m spacing in full sun but close to native flowering trees (Fig. 6 & 7). The butterfly

prefers open and flat sedgeland for mating displays and females need clear accesses to the side of the tussock to

lay their eggs (Fig. 7). Habitats for this butterfly can be quite small. Populations are known to breed on clumps of

only 150 plants (30 juvenile).

Figure 6: Guarded Gahnia filum (Thatching Grass) seedlings at

Salisbury Greenfields 3 Wetlands Photo: C. Butcher

Figure 7: Small established Thatching Grass sedgeland with

Melaleuca trees at Minlacowie Swamp. Photo: C. Butcher

*Also Gahnia deusta (Heathy Saw-sedge)

Thatching Grass information sheet

Threats to Thatching Grass and Yellowish Sedge-skipper

Thatching Grass and YSS populations can be protected by limiting threats. Some of these

threats are:

- Direct clearance: Intentionally clearing Thatching Grass limits the overall YSS habitat

size on southern Yorke Peninsula. Clearing can also increase the risk of the area being

affected by soil salinity where it if cleared. The benefits of having a stand of Thatching

Grass can greatly outweigh the benefits of clearing it.

- Over-grazing: Thatching Grass is not generally a preferred plant for grazing but both

domestic (especially cows) and native grazers can damage the plant. Grazers also

compete with the YSS larvae for the fresh leaves and sometimes the larvae can be

eaten along with the leaves.

- Over-crowding: If the females cannot access the side of the plants then it is likely that

fewer eggs will be laid. Furthermore, over-crowding the tussocks increases

competition for sunlight, soil nutrients and water.

- Spray drift: Fertilisers, herbicides and pesticides can harm both the plant and the YSS

in different life stages (i.e. egg, larval or mature). Furthermore, they can kill beneficial

predators and parasites that control introduced pests (e.g. Western Flower Thrip).

- Change in water cycle: The plants thrive in the wetting/drying cycle of a swamp/

wetland. It may no longer be viable as a YSS habitat if the water cycle is changed by

draining the land and altering drainage flows.

More information

Councils, state government, NGOs and more: Local and state government agencies are working together with non-

government organisations and volunteer groups to help improve the Thatching Grass habitat for the Yellowish Sedge-

skipper. Visit their websites or offices to discuss what you want to know or how you can help.

Natural Resources Northern and Yorke, and Natural Resources Adelaide Mt Lofty Ranges

Nature Conservation Society of South Australia (NCSSA)

City of Salisbury, City of Playford and Adelaide Plains Council

Management plans and projects: One of the founding documents for this effort is the Local Recovery Plan for the Yellowish

Sedge-skipper and Thatching Grass. The Local Recovery Plan helped lead to the inclusion of our butterfly and its habitat as

conservation priorities in the Metropolitan Adelaide and Northern Coastal Action Plan. The plan was reviewed in 2015 to see

how close we were to reaching our goals. The NCSSA has completed a feasibility assessment for the reintroduction of the

species.

Coleman, P & Coleman, F (2000) Local recovery plan for the Yellowish Sedge-skipper and Thatching Grass. Saint Kilda, South Australia: Delta

Environmental Consulting.

Coleman, P (2015) Progressing the Local Recovery Plan: Yellowish sedge-skipper butterfly & Thatching Grass. Prepared for: Natural Resources

Adelaide & Mt Lofty Ranges and Australian Government, Samphire Coast Icon Project Biodiversity Fund.

Caton, B, Fotheringham, D, Krahnert, E, Pearson, J, Royal, M and Sandercock, R (2009) Metropolitan Adelaide and Northern Coastal Action

Plan. Prepared for Adelaide & Mount Lofty Ranges Natural Resource Management Board and Department for Environment and Heritage,

Adelaide.

Butcher, C (2017) Yellowish Sedge-skipper Butterfly Reintroduction Feasibility Project – Final Report. Prepared for the Nature Conservation

Society of South Australia for the Adelaide and Mt Lofty Natural Resources Management Board (Samphire Coast Icon Project).

Specialist pest management research: There a some very promising work done towards using native plants (and animals) as

part of an integrated pest management strategy. This is specifically targeted at common horticultural pests.

RIRDC (Rural Industries Research and Development Corporation) (2011) Revegetation by Design - Promoting the ‘on-farm’ use of native

vegetation as agents of ‘natural pest control’. RIRDC Publication No. 11/002. Canberra: Union Offset Printing.

Wood, G and Coleman, P (2016) Gahnia filum: Insect use of Thatching Grass. Prepared for: Adelaide and Mt Lofty Ranges Natural Resource

Management Board.

Other research from the literature: A large part of what we know about our butterfly’s habitats on the southern Yorke

Peninsula is because of the work done by Alex Stolarski, Roger Grund and Butterfly Conservation South Australia. There has

been a great deal of research on butterfly conservation in Australia, including the close relative Hesperilla flavescens

flavescens in Victoria, by specialist researchers.

Grund, R (1997) Interim Recovery Plan. Recovery of Hesperilla flavescens flavia (Lepidoptera: Hesperiidae), the yellowish skipper. Report to

National Heritage Trust, Canberra.

Grund, R (2003) The yellow sedge-skipper on Yorke Peninsula. Prepared for Butterfly Conservation South Australia Inc.

New, T (2011) Butterfly conservation in South-Eastern Australia. 1st ed. New York: Springer, 55-65.

New, T and Sands, D (2002) Conservation Concerns for Butterflies in Urban Areas of Australia. Journal of Insect Conservation, 6(4), 207-215

New, T and Sands, D (2004) Management of threatened insect species in Australia, with particular reference to butterflies. Australian Journal of

Entomology, 43(3), 258-270.

Relf, M and New, T (2009) Conservation needs of the Altona Skipper butterfly, Hesperilla flavescens flavescens Waterhouse (Lepidoptera:

Hesperiidae), near Melbourne, Victoria. Journal of Insect Conservation, 13(2), 143-149.

Savage, E (2002) Options and techniques for managing Chaffy Saw-sedge (Gahnia filum) as habitat for the Altona Skipper butterfly (Hesperilla

flavescens flavescens). Conservation and environmental management, occasional paper series. Parks Victoria, Melbourne.

For more information - Email: ncssa@ncssa.asn.au | Phone: 08 7127 4630