Looking after the Arid Bronze Azure Butterfly
We understand that the population of Arid Bronze Azure Butterfly (Ogyris subterrestris subterrestris) on our property is the largest population in Australia. Now, recent research (1) has listed “our” butterfly as #7 on a list of 26 butterflies most likely to go extinct in the next 20 years. Gulp. No pressure then.
The discovery of the Arid Bronze Azure butterfly on Raakajlim played a big part in our decision to protect our entire property forever with a conservation covenant. Here’s the story:
The Arid Bronze Azure caught mid “wing-flap”, showing the beautiful bronze and azure coloring.
In their usual, wings-closed position, the butterfly is well camouflaged.
In March 2002, our friend and entomologist Fabian Douglas visited us during his search for the Arid Bronze Azure butterfly. Fabian searched likely habitat in Hattah Kulkyne National Park for many days and was feeling quite dejected; there were just no butterflies to be found. To cheer him up, we took Fabian to show him one of our rare plants (Skeleton Fanflower Scaevola depauperata). I remember that morning well. Fabian started leaping through the air with his butterfly net, dashing about and shouting “They’re here!!!”. A few more days of surveying in HKNP revealed that the butterfly population was predominantly on our land. Fabian gifted us a copy of Michael Braby’s Butterflies of Australia and told us to look after them …
We were unsure what looking after the butterfly entailed so we did some research. We learnt about the strange, ancient and highly specialised association with a species of nocturnal sugar ant (Camponotus terebrans, but we call them Piss Ants). Our butterfly is myrmecophagous (ant-eating), and that’s quite weird (2). The butterfly eggs are laid near the entrance to an ant nest and the entire butterfly larval stage is completed within the nest. The caterpillar is a predator of immature ants but it somehow manages to fool the ant colony into continuing to look after it. Because the adult butterflies are sedentary, protection of existing populations, and their host ant, is critical. Floristically diverse habitats are needed to sustain the required high densities of the host ant.
Piss ants clustered gleefully around where a kangaroo has urinated.
Mating butterflies, with the larger female on the right.
We are not entomologists but “floristically diverse habitat” we understand very well! We focus on improving the habitat on our land by managing grazing pressure, weeds and undertaking revegetation. Grazing pressure from kangaroos is our big challenge, now that we have the rabbits under control. Our biggest project is completing a 13 km kangaroo fence around our property (finished March 2022!). This will allow increased natural regeneration of the plants which kangaroos love to eat. It will also allow us to undertake more revegetation, and even small burns, to enhance the habitat for the butterfly and its attendant ant.
Aside from the strange caterpillar-eating-ant relationship, Ogyris subterrestris is also an example of east-west species divergence. Our butterfly is the eastern subspecies and the critically endangered O. s. petrina (3, 4) is the matching subspecies found in Western Australia (#11 on the extinction list). The Nullabor Plain emerged as a bio-geographical barrier with the onset of aridity and throughout the Pleistocene, splitting the mesic (moister) areas into east and west. For the Arid Bronze Azure, the split occurred about three million years ago and the two subspecies have continued to evolve separately. There have been some serious genetic studies of this “phylogeographical divergence” seeking to understand how environmental change has shaped species evolution (5).
It feels like a heavy responsibility that the survival of a species might be depending on you, but it’s a great reminder that bigger is not always better. Small areas managed for conservation, even on private land, make an important contribution to the protection of threatened species, including birds (6), plants (7) and invertebrates (8). A recent global study encouraged us to recognize the critical role that small patches play in conserving the world’s biodiversity (9). So we will continue to focus on enhancing our small patch of safe habitat for butterflies, and the many plants and critters that call the Mallee home.
We'd love to hear from anyone willing to share their knowledge on how best we can conserve this butterfly.
Further reading:
“Next time you see a butterfly, treasure the memory” - https://theconversation.com/next-time-you-see-a-butterfly-treasure-the-memory-scientists-raise-alarm-on-these-26-species-159798 and the original article Geyle et al. (2021) Butterflies on the brink: identifying the Australian butterflies (Lepidoptera) most at risk of extinction https://onlinelibrary.wiley.com/doi/10.1111/aen.12525
Arid Bronze Azure and ants - a bizarre relationship https://particle.scitech.org.au/earth/three-natures-bizarre-relationships/
Our entry into the 2020 Threatened Species Day cake decorating competition (https://www.malleeconservation.com.au/blog/ogyris-bakeoff).
DPAW (2020) Arid Bronze Azure butterfly (Western Australia) https://www.dpaw.wa.gov.au/plants-and-animals/threatened-species-and-communities/threatened-animals/562-arid-bronze-azure-butterfly
Schmidt et al. (2014) Australian parasitic Ogyris butterflies: east-west divergence of highly specialised relicts. Biol. J. Linnean Society: 111(2): 473-484. https://academic.oup.com/biolinnean/article/111/2/473/2415902
Belder et al. (2019) Is bigger always better? Influence of patch attributes on breeding activity of birds in box-gum grassy woodland restoration plantings. https://www.sciencedirect.com/science/article/abs/pii/S0006320718313478
Kendal et al. (2017) The importance of small urban reserves for plant conservation https://www.sciencedirect.com/science/article/abs/pii/S0006320716306747
New et al. (2020) Roles of roadside vegetation in insect conservation in Australia https://onlinelibrary.wiley.com/doi/full/10.1111/aen.12511
Wintle et al. (2019) Global synthesis of conservation studies reveals the importance of small habitat patches for biodiversity https://www.pnas.org/content/116/3/909?sfns=mo&sfns=mo