Protecting the pale imperial hairstreak butterfly
Landholders offer rare sanctuary for critically endangered butterfly
The existence of one of Australia’s most endangered butterflies, the pale imperial hairstreak, has been confirmed, however its fate depends on how well a small region of unique brigalow woodland can be maintained, managed and preserved for the future.
The regally named pale imperial hairstreak (Jalmenus eubulus) is listed as critically endangered, making its home exclusively in the likewise endangered brigalow woodlands of North West NSW. It has the unfortunate distinction as the second-most likely butterfly in Australia to go extinct in the next 20 years, after the bulloak jewel. Like the bulloak jewel, the decline of the pale imperial hairstreak is linked to habitat loss and hence the ecosystems which support its unique life cycle.
There are only a few recorded sightings of the pale imperial hairstreak since the mid-1970s, all in brigalow woodlands in northern NSW near the Queensland border around Boggabilla and North Star. This area has some of the only remaining healthy, remnant brigalow woodland in NSW, which has been reduced to less than 10 per cent of its original area.
It’s also critical to the pale imperial hairstreak, which lays eggs only on young brigalow (Acacia harpophyll)leaves, that are the exclusive diet of emerging caterpillars. Adults feed on the nectar of flowers on other flora found only in these woodlands and spend their entire life around the brigalow tree they were hatched on.
Sight to behold
Those who have seen the pale imperial hairstreak include landholders Tim and Kerrie Hayes, along with a handful of ecologists who’ve undertaken surveys on their farm and around the district over the years.
Their property features one of the largest, healthiest and most intact stands of remnant brigalow remaining in NSW, providing an oasis for the pale imperial hairstreak. This woodland is dominated by the presence of brigalow and/or belah (Casuarina cristata) usually with scattered eucalypts such as poplar box (Eucalyptus populnea) and low understory trees such as wilga (Geijera parviflora).
The Hayes and the hairstreaks live on the western edge of what was previously known as the ‘Mungle Scrub’ – a vast bioregion of brigalow woodland once covering around 150,000 acres.
The history of the Mungle Scrub is an interesting and chequered one. It’s been a victim of the richness of its soils and hence suitability for farming and grazing. At the turn of the century the scrub was largely intact, however much of the area became infested with prickly pear and was practically impenetrable for both animals and humans.
As a result the NSW Government of the day introduced the cactoblastis moth, which quickly decimated the pear. Portions of the scrub were then balloted among existing landholders during the 1940s and 50s, with a stipulation it be cleared and farmed.
With only fragmented patches and strips remaining, a 400-hectare patch of brigalow on the Hayes’ property is a rare survivor. This stand of healthy, remnant brigalow scrub still exists due to the foresight of Kerrie’s father who would not clear it, despite the government mandate.
Photo credit: Phil Bell
A collaborative approach to habitat conservation
When Tim and Kerrie took over the farm, they also could not bring themselves to clear it and also maintained another 50 hectares of brigalow in tree lines. They are passionate about preserving it and have been working with Pippa Jones from North West Local Land Services (North West LLS), ecologists and CSIRO to better understand and manage it. This has included support for invasive weeds control, quantifying the ecosystems services it provides and surveys for the pale imperial hairstreak.
Pippa worked with Terry Mazzer from the NSW Department of Planning and Environment (DPE) through its Saving our Species program to undertake a survey in 2022 at various locations in the Boggabilla/North Star area. The pale imperial hairstreak was located at four sites, and importantly, found to be breeding at three of those, including at the Hayes’.
Threatened species ecologist Phil Bell undertook the surveys.
“The future of the pale imperial hairstreakdepends on these core breeding sites within its shrinking habitat,” Phil said.
“It goes without saying that if the brigalow woodland is under threat, so is anything that relies on it for survival.
“We found that pale imperial hairstreak habitat is in fragmented, small patches including travelling stock reserves or roadsides.
“That the species was found on two of the four properties we had access to is remarkable and has extended our understanding of distribution in particular on private land around North Star and Boggabilla.
“However, a landscape view of the study area revealed that the properties involved in the survey include some of the most significant remnant and old growth patches of brigalow remaining in the easterly distribution of this forest community in NSW.”
Landholders key to conservation of core breeding sites
As such, Phil says Tim and Kerrie are extremely important for conservation of the species.
“It was exciting and really fantastic to see them and other landholders so enthusiastic,” Phil said.
“We really appreciate them allowing us to survey, as it is rare to find these brigalow communities in such good ecological condition and in decent clumps.
“What is fantastic is that the landholders are keen to maintain the brigalow.”
While Tim and Kerrie knew the butterfly was still around, although rarely seen, the confirmation was great news to them and validates their decision to preserve this woodland.
“The ecologists tell us this butterfly is known to only breed in old-growth brigalow woodland and doesn’t appear to colonise in regrowth brigalow after it is cleared,” Kerrie said.
“We manage around 450 hectares of healthy, old-growth scrub, which represents a third of our farm, but it is critical for the butterflies and everything else that relies on it.”
There are several species of birds and reptiles endemic to brigalow woodland, which operates like a single functioning organism, with interdependency among species.
In an unlikely alliance, after the pale imperial hairstreak lays its eggs in lower storey brigalow trees, small, black ants (Iridomyrmex) move in to guard them and in turn feed on honeydew secreted by the larvae and pupae when the eggs hatch.
These interdependent/symbiotic or ‘obligate’ relationships make an animal more prone or exposed to collapse.
“Added to its dependence on a single species of host plant, the species remains at a high risk of extinction in NSW,” Phil said.
Terry Mazzer agrees.
“If you look at a situation in isolation, you might think, if we lose a few ants that’s not significant,” he said.
“However, if we lose any more remnant brigalow, or just these ant populations within it for any reason, then the butterflies are next.
“It really highlights the need to look after what brigalow woodland we have left, for all the species it supports.”
Lifelong interest in biodiversity
The Hayes’ property offers this rare glimpse into this complex ecosystem.
Tim is a keen observer, always on the lookout and often with camera in hand, when he’s not planting or harvesting crops.
As well as butterflies, over 50-odd years of constantly observing he and Kerrie have spotted and recorded more than 80 species of animals and birds such as the (vulnerable) painted honeyeater and striated pardalote. They’ve also spotted the red-naped snake, eastern bandy-bandy, the endangered pale-headed snake and several species of legless lizards.
The Hayes are continuing to work with North West LLS to explore pathways to ensure the brigalow woodland can be maintained and protected in the future. Tim says it’s about taking the long view on the consequences of their actions as landholders while finding a way to alleviate the cost of keeping and maintaining these areas in the short term.
“The way we behave, the decisions we make and how we manage our farms in our one lifetime needs to be considered.
“That we are only here for short time, I think that has been forgotten and needs to be relearned as the decisions we make on our farms in our lifetimes can directly affect huge issues such as the future of a species.
“And it’s not just those on the brink like the pale imperial hairstreak either, to me it represents all the amazing animals, birds and insects that live in ecosystems like these old-growth brigalow woodlands.
“If Kerrie’s father hadn’t saved the scrub on this farm, we wouldn’t be having this conversation today.”
By the same token, conservation costs a lot of money in the form of avoided income by not farming it, along with keeping the brigalow healthy and free of weeds and pests.
“We spend between $20,000 and $30,000 per year for weed control in the 400-hectare block, and we could easily be spending more to keep on top of it as recent wet years have increased germinations and the survival of invasive species,” Tim said.
Calculated over the last 50 years, avoided income would be in the millions of dollars. While they wouldn’t change what they’ve done, Tim and Kerrie naturally worry if it will all have been worth it if it is not preserved for the future.
“We worry what will happen to the remaining brigalow here when we aren’t here anymore, because we know how valuable it is as farming land, and from an economic standpoint it would make sense to clear it.
“But we have a responsibility to nature, the landscape and these ecosystems to preserve them.
“There are some things that are more valuable than money, but it can be difficult to do it alone, that’s why we are working with government bodies like LLS to find a way to manage and preserve it for the future of all species.”
A complicated life
The pale imperial hairstreak is no typical butterfly: it needs the right species of ant to complete its life cycle, it lives in colonies, adults have an association with mature brigalow but only find pupae on young plants. It also hangs around the same plant it is born on.
“While in themselves these may seem like simple factors, if they don’t all come together, we have no butterfly,” Phil says.
“As a ‘sedentary’ species, adults don’t stray far from the food plant they were born on and is probably why we end up with colonies and distinct patches where we find them.
“This does leave them exposed to things such as drought, fire, or pesticide drift, which could potentially wipe out one of the only three colonies we have found in NSW.
“They might disperse from a site, but the chances of finding a new one in such a fragmented landscape that is biodiverse enough to support them is low – for a start the ants would have to be there as well.”
Can we move them?
By working with landholders, ecologists now have a better understanding of the butterfly’s preferred habitat within the brigalow ecosystem. This knowledge is valuable for revegetation and conservation efforts and also help any attempts at translocations if more critical habitat is lost.
When a species is as vulnerable and rare as the pale imperial hairstreak, ecologists often turn to translocation to save them, moving them into new habitats in the hope they will colonise there. Precious examples have seen birds such as the regent honeyeater bred in captivity and released into previously inhabited regions.
“We’ve identified translocation as a possible measure that may have to be explored,” Phil said.
“This would involve extending the distribution of the hairstreak in the vicinity of known colonies and on neighbouring properties supporting potential habitat.
“Additional information is also required on the distribution, extent and ecological requirements in order to construct appropriate, feasible and effective management actions for the species, and inform the development of a site managed project for delivery through the SoS program.”
The project is supported by North West Local Land Services with funding from the Australian Government’s National Landcare Program.
Surveys were undertaken in 2017 and 2013, when the butterfly was known from only one record in NSW from a sighting 35km south of Boggabilla in 1977. The 2013 surveys found adults at four locations in the vicinity of the 1977 site.