Fighting for fire’s smallest victims

Detailed summary

Scientists are mapping the traits of our invertebrate species to help them survive more frequent and severe fire events.

Dr Jess Marsh has long held a curiosity for a charismatic arachnid called the Kangaroo Island assassin spider (Zephyrarchaea austini). Measuring a mere 3mm in length, it’s a difficult species to find. But under the microscope its awkward beauty is evident. It has an elongated head and long mouth parts, which give it an elegant appearance similar to that of a pelican – and an advantage when hunting.

Spider expert Jess, a researcher at Adelaide University and co-founder of not-for-profit Invertebrates Australia, has lived on South Australia’s Kangaroo Island (KI) for almost two decades. “I’ve watched a female assassin spider hunt before. It was like something out of [sci-fi novel and movie] The Day of the Triffids,” she says, referring to how the spider slowly and patiently stalks smaller prey before launching a rapid strike.

The critically endangered KI assassin spider hails from an ancient lineage; some of the species’ oldest related fossils date back 160 million years. It’s a solitary species that’s believed to be fairly long-lived and only produces a small number of young each year. The 2019–20 Black Summer bushfires destroyed all of its then-known habitat, inspiring Jess to begin surveying for the spider in earnest.

“I took photos two months after the Black Summer bushfires and all the organic material was gone,” Jess says. “It was so severe that in some places the soil was burned down to rock. We had serious concerns that the species could have been driven to extinction then and there.”

The KI assassin spider lives in leaf litter suspended at about human knee height in scrubby heathlands and open eucalypt woodlands. It’s found most often along creek lines and gullies where rainfall is high. “It’s a really flammable microhabitat,” Jess explains. “When fires go through, the first thing that burns is the elevated leaf litter because there’s so much air flow around it.”

For ancient species such as the assassin spider, fire isn’t a new pressure.

Following the most recent…

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