Fight to save a very-Victorian butterfly, amid global biodiversity decline

In Victoria, there’s an official state animal, bird, flower, fossil, and even a mineral (gold, of course). 

While the south-eastern state is yet to claim an insect emblem, the Golden-rayed Blue Butterfly might make a suitable candidate.

This small butterfly – with a wingspan smaller than 3cm – is named for its soft purply-blue wings delicately lined with golden veins.

The Golden-rayed Blue (Candalides noelkeri) is the only butterfly known to exist exclusively in Victoria, says Michael Magrath, Zoos Victoria’s senior research manager, who coordinates the organisation’s efforts to conserve threatened species. 

When the butterfly was first described 20 years ago, it was found at the margins of a handful of salt lakes in the Wimmera River system, he says. 

Today, the very-Victorian butterfly’s habitat is restricted to remaining narrow bands around the lakes not yet been cleared for agriculture.

“Probably not helping the butterfly’s cause, it also appears to be completely dependent on one plant species for food at both the larval and adult stage – Creeping Boobialla (Myoporum parvifolium) – which is an attractive ground cover plant that produces a mass of small white flowers,” Magrath says.

A survey by local entomologist Fabian Douglas in 2021 found the Golden-rayed Blue Butterfly at twelve different locations, including six previously unknown sites, extending the butterfly’s previously known range further north and south. 

Magrath says, despite this positive news, at some of the locations where the endangered butterfly occurs, its food plant is not doing well and is being displaced by invasive weeds and even a native paperbark. 

Little wonder scientists named the species among a list of 26 Australian butterflies at greatest risk of extinction.

A new global study by Queen’s University Belfast published in Biological Reviews tracking biodiversity population trends across 71,000 animal species and insects, found nearly half (48%) are undergoing declines. The extent of declines greatly exceeds species increasing (3%).

The study suggests 54% of insect species populations are in decline, although the proportion of species with unknown population trends was much higher for insects due to lack of data, compared to birds, mammals, reptiles, and amphibians. 

For the Golden-rayed Blue Butterfly, Zoos Victoria is working to support a range of actions aimed at gaining a better understanding of the species and reducing its risk of extinction, working with partners including Trust for Nature, the Dalki Garringa Native Nursery and local landholders. 

Part of these efforts involve re-vegetating the endangered butterfly’s Myoporum food plant. 

Cuttings have already been collected from local plants and reared at the Dalki Garringa Native Nursery, operated by the Barengi Gadjin Land Council, with planting underway at selected sites this autumn.

Magrath says the focus will then be on monitoring whether the new plantings can attract Golden-rayed Blue Butterflies to sites that are currently unoccupied.

He says butterflies “are one of the most loved group of insects, well-known for their visibility, array of colours and distinct flight”.

Zoos Victoria has had interest and offers from a number of local landholders and community groups who would like to be involved in either the revegetation work or surveys for the butterfly.

One of the best things people can do to support endangered butterflies is to plant butterfly-attracting shrubs and trees which are native to their local area, he says.