Environmental group discovers largest population of the nationally endangered Eltham Copper Butterfly

Wetland Revival Trust's (WRT) long term butterfly project in northern Victoria discovered the largest population of the nationally endangered Eltham Copper Butterfly (ECB) (Paralucia pyrodiscus lucida) at two Gerang Gerung nature reserves.

Elaine Bayes, an ecologist from Wetland Revival Trust, a not-for-profit environmental charity, has been involved in the protection of this tiny butterfly since 2009.

Elaine started a search and find mission in 2019 in north central Victoria, where there are several ECB populations.

The search spread to the Wimmera which may be the prime location for this species.

Elaine said ECB numbers at the two very small known populations in the Wimmera were at much higher densities than in the north central where a search had been carried out.

"This year, our team searched 1600 hectares of public land for the butterflies, 1400 ha of which was in the Wimmera and we were certainly rewarded for the effort, with around 500 ECB seen between the two Gerang Gerung reserves," she said.

"To give perspective, in north central Victoria last year, we searched 1000 ha and found a total of 43 ECB peppered across a large area. To see 500 ECBs in one season is exceptional, and so far, this is the largest number of ECB and the largest area of ECB habitat ever found."

This search was funded be the Victorian Government Biodiversity On-ground Action Program (Icon Species Projects) which supports actions to protect nationally endangered species like ECB.

ECB were first found in the Wimmera in 1988 at Salisbury Bushland Reserve and in a small area of Kiata Flora Reserve.

In 2011, another tiny population (six hectares) was found on a Wail roadside by local entomologist Fabian Douglas.

In the intervening years, the Salisbury population became extinct, believed to be caused by sheep grazing out the butterfly's food plants.

The two remaining populations at Kiata and Wail are separated by a sea of agriculture, with nowhere for their young to disperse to.

There is no way for the populations to move around as environmental conditions change, and no corridors of native vegetation for the butterflies to move along so they can share DNA to make them more resilient.

Also being small the sites are under threat from pests, weeds and roadworks.

Elaine believes that part of the reason ECB is rarely seen is that they require very specific conditions.

As well as being dependent on one plant species to feed their larvae, the Sweet Bursaria (Bursaria spinosa), they require one specific ant species (Notoncus ectatommoides) to act as a bouncer for their larvae, scaring off predators that would otherwise feast on their juicy bodies.

Their other very specific needs are that these delicate little butterflies are solar powered and only fly when it is 20-30 degrees with no wind or rain.

The adults only emerge when there is abundant nectar around November and December usually peaking at Christmas and New Year (with a smaller emergence in March and April).

Finding field staff to search for ECB at Christmas and New year is as rare a thing as finding the ECB themselves.