Australia (Commonwealth)_
For the past five weeks, conservation biologist Jane Ogilvie, associated with the charity Invertebrates Australia, has been carefully searching a specific area of dense shrubbery shaded by sugar gums on Kangaroo Island, South Australia. Her mission is to find a surviving specimen of the critically endangered Kangaroo Island assassin spider, a remarkable creature that has existed for an astonishing 150 million years. This Jurassic-era arachnid is known to live only in the north-west part of the island, where it usually hides in damp clumps of leaf litter. Despite more than a month of focused searching by Ogilvie and her assistants, they have found only one tiny juvenile, with just a couple of weeks left in their search period. Ogilvie shared her mixed feelings of excitement and disappointment. She felt thrilled when she initially located a promising area but then disheartened by the extremely dry conditions. She pointed out that the region has seen very little rainfall for the past two years.
Last year, scientists recorded just one mature female and six juveniles across six different locations, all within a 20 square kilometre area. This area includes a piece of land owned by mining magnate Andrew Forrest. However, this year, those same locations have produced no new sightings of the spiders. The survival of these unique spiders heavily relies on the moist microclimate created by leaf litter. Unfortunately, a combination of three major threats is quickly drying out their habitat, pushing them closer to extinction.
The spider’s last refuge has faced a near-record drought over the past 18 months, with rainfall levels among the lowest recorded since 1900. Additionally, the devastating Black Summer bushfires burnt through large areas of potential habitat that have yet to recover. To make matters worse, an invasive plant root disease called phytophthora is damaging the forest canopy and the very plants that support the leaf litter where these spiders live. Dr Michael Rix, the principal scientist and curator of arachnology at the Queensland Museum, who played a key role in collecting and formally describing the spider’s first specimens with his colleague Mark Harvey, commented on the serious situation. He said that realistically, the spiders might be just one major fire away from extinction, emphasizing that their survival is extremely uncertain.
The Kangaroo Island assassin spider is one of eleven invertebrates listed on the federal government’s priority list of threatened species. The assassin spider family, named for their unique method of quietly stalking and consuming other spiders, is found only in Australia, Madagascar, and parts of southern Africa. The Kangaroo Island species was first identified in 2010 by Dr Rix, who, along with Dr Harvey, has described 37 of Australia’s 41 known assassin spider species. Dr Rix recalled the memorable time of discovery, describing how they would collect and shake suspended leaf litter, prompting the spiders to drop down with their legs closed. When he examined the tray, he immediately recognized the unidentified species, marking it as one of the most exciting moments in his career in field biology. Dr Rix stated that their appearance is truly unusual among spiders, noting their “incredible elevated heads and long spear-like mouth parts.” He affirmed their distinctiveness and highlighted their role as an early branch in the spider’s evolutionary tree. Assassin spiders are ancient beings, with those alive today representing survivors of 150 million years of life on Earth. He also explained that these spiders were previously known only through fossils until live specimens were first discovered in Madagascar in the 19th century.
The Kangaroo Island species was sadly thought to be extinct after the bushfires of 2019 and 2020 swept through the western part of the island during the Black Summer. However, Dr Jess Marsh, a research fellow at the University of Adelaide and an invertebrate conservation biologist based on Kangaroo Island, provided a glimmer of hope by finding two specimens in 2021 within a small, unburned patch of vegetation. Dr Marsh noted that the spider’s habitat is being “squeezed into smaller and smaller areas,” and each survey only reinforces the belief that its presence is limited to this shrinking patch of vegetation.
Dr Marsh and her colleagues are now considering starting a breeding program for these spiders in a zoo to create an “insurance population.” However, she recognises the significant risks associated with removing individuals from their natural habitat. She reflected on the spiders’ incredible resilience, having survived numerous mass extinction events and past climate changes, and noted that in this relatively short time, human activities are truly testing their endurance. Dr Rix addressed the potential question of why a tiny spider going extinct matters, explaining that it reflects a larger, measurable loss of invertebrate species happening right now. He warned that this issue might “creep up on us” without being noticed. He emphasized the importance of conserving evolutionarily significant units, which involves preserving diversity that reflects Earth’s evolutionary history. He pointed out that these spiders embody this concept, acting as a “window into the past” and true survivors, making their conservation crucial.
In a surprising turn of events this week, a 17-year-old volunteer named Jack Wilson, who was helping out during his school holidays, made an important discovery. Until then, Dr Marsh and Dr Rix were the only two people who had ever found a Kangaroo Island assassin spider. Wilson described his discovery, noting it was probably his tenth sieve of the day. He mentioned that the spiders can look like small clumps of dirt, but their distinctive “big neck” gives them away. Expressing his excitement, he simply said, “It’s crazy.”
