--- title: "Sydney Funnel-Web Spider (Atrax robustus) | AnimalTracks.wiki" description: "Male venom carries a nerve toxin that likely evolved to deter bandicoots and birds, and is lethal to humans by unfortunate coincidence." image: "https://animaltracks.wiki/images/animals/sydney-funnel-web-spider-1.webp" published: "2026-09-01" updated: "2026-09-24" --- # Sydney Funnel-Web Spider (*Atrax robustus*) > **Status**: Checked against 10 sources, listed under Sources below. > **Tagline**: Male venom carries a nerve toxin that likely evolved to deter bandicoots and birds, and is lethal to humans by unfortunate coincidence. > **Soundtrack Vibe**: Classic Hard Rock & Southern Blues // Joan Jett & the Blackhearts, "Bad Reputation" > **Soundtrack Links**: [Spotify](https://open.spotify.com/track/3VwCHFahYwyUSR0Rse4Boo) > **Vibe Match**: A snarling, stomping warning of a chorus, for a spider that, if threatened, rears up and displays its fangs. ## Biological Superpowers & Stats - **Taxonomy**: *Atrax robustus* - **Danger Level**: Deadly - **Conservation Status**: Not Evaluated ([IUCN Red List](https://www.iucnredlist.org/)) - **Superpower**: Robustoxin (delta-atracotoxin-Ar1), a 42-amino-acid peptide in male venom that stops some sodium channels in nerve cells from switching off properly. Its toxin family likely evolved to deter vertebrate predators such as bandicoots, birds and lizards, but robustoxin severely affects the nervous systems of humans and monkeys. - **Habitat**: Shady gullies, forest, woodland and bushy suburbs across the Sydney basin, from the Central Coast south to the Georges River and west to Baulkham Hills - **Diet**: Beetles, cockroaches, millipedes, small lizards and land snails - **Tags**: arachnid, burrower, venomous ## Natural History & Behavior ## A Toxin Built for the Wrong Target Only male Sydney funnel-webs (*Atrax robustus*) are known to make venom molecules that cause serious effects in humans. The key one, robustoxin, also called delta-atracotoxin-Ar1, is a chain of 42 amino acids folded into a knot and held together by four sulfur-to-sulfur bridges. In tests on rat nerve cells, it stopped some sodium channels, the pores that let a nerve fire, from shutting off properly: a trickle of sodium kept flowing, and the channels reset faster for the next signal. Those changes fit with funnel-web toxins making nerves fire over and over. > **An Evolutionary Coincidence** Robustoxin severely affects the nervous systems of humans and monkeys, but not those of other mammals. A 2020 study found it causes pain in mice and concluded that this family of funnel-web toxins likely evolved to deter predators such as bandicoots, birds and lizards. Humans are not the target, which makes the toxin's lethal effect on us "an unfortunate evolutionary coincidence." ## Two to Four Centimetres, Grown Up in Year Five A Sydney funnel-web measures 2 to 4 centimetres, according to the Australian Museum; Animal Diversity Web gives males up to 25 millimetres and females up to 35. It's a shiny, dark brown to black spider with finger-like spinnerets, its silk-spinning organs, at the tip of the abdomen. It is long-lived for a spider: females can live for more than eight years, and both sexes generally mature only in their fifth year. Females tend to stay in one place unless flooding forces them out. Males mature in summer and leave their burrows, usually after rain, to roam in search of mates. ## Ambush From a Silk Trip-Wire Sydney funnel-webs live in silk-lined burrows under logs and rocks, where the air stays cool and humid, with silk trip-lines laid around the entrance. The spider waits just inside, and when a beetle, cockroach, small lizard or millipede walks across a line, it rushes out to grab it, then carries the meal back into the burrow. Threatened, it rears up and displays its fangs. In a 2022 lab study, juveniles tended to huddle when puffed with air, while adults lifted their front legs and moved their fangs. ## One Spider Becomes Three The Sydney funnel-web lives in shady gullies, forest and bushy suburbs from the Central Coast south to the Georges River and west to Baulkham Hills, with some records from the Blue Mountains and Wollongong. More recently its range has shrunk in the south. It was long considered a single species. A 2025 study, combining DNA with detailed anatomy, split it into three: the "true" Sydney funnel-web centred on Sydney's North Shore and the Central Coast, the Southern Sydney funnel-web (*Atrax montanus*), most common in the Blue Mountains, and the Newcastle funnel-web (*Atrax christenseni*), the largest of the three. Decades of venom research on spiders then all called *Atrax robustus* now need re-examining in light of the split. ## Frequently Asked Questions ### Why did scientists split the Sydney funnel-web into three species in 2025? What looked like one unusually variable species turned out to be three. Researchers who compared DNA and fine anatomical detail across the Sydney region found differences showing that three species should be recognised. They also noted that the large body of venom research published under the name Atrax robustus has to be looked at again in light of the new classification. *(Source: [Loria et al. 2025]())* ### Can funnel-web spiders really survive at the bottom of a swimming pool? For a while. Funnel-webs that fall into backyard pools can stay alive for at least 30 hours underwater. They can't swim, but a small bubble of air trapped in the hairs around the abdomen helps them breathe and float. As they slowly get waterlogged they sink and eventually drown, but it takes a long time, and a motionless funnel-web at the bottom of a pool often recovers. *(Source: [Australian Museum]())* ### Why are male Sydney funnel-webs considered more dangerous than females? Male venom contains robustoxin, which severely affects the human nervous system. Its absence from female venom probably explains why bites from females have not caused any deaths, though the Australian Museum warns that no funnel-web bite should be assumed safe. Males are also the ones people tend to meet: in the warmer months, November to April, they wander through gardens at night looking for mates, and sometimes end up trapped inside a house or garage. *(Source: [Australian Museum]())* ### Has a Sydney funnel-web spider bite killed anyone recently? Not since 1981, when Dr Struan Sutherland's team at the Commonwealth Serum Laboratories first developed an antivenom for clinical use. The Australian Museum records no deaths since its introduction. Funnel-web bites caused thirteen recorded deaths, and the male Sydney funnel-web, as the species was understood before its 2025 split, is probably responsible for most of them. The antivenom has also worked against other dangerous funnel-web species. *(Source: [Australian Museum]())* ## Sources 1. [Sydney Funnel-web Spider, Atrax robustus. Australian Museum.]() 2. [Australian Funnel-web Spiders. Australian Museum.]() 3. [Australia's deadliest spider reclassified. Australian Museum.]() 4. [Atrax robustus. Animal Diversity Web, University of Michigan.]() 5. [Loria et al. (2025). The world's most venomous spider is a species complex: systematics of the Sydney funnel-web spider (Atracidae: Atrax robustus). BMC Ecology and Evolution.]() 6. [Duran, Wilson & Lee Rymer (2022). Behaviour of the Sydney funnel-web spider Atrax robustus over different contexts, time, and stimuli. Toxicon: X.]() 7. [Nicholson et al. (1998). Characterisation of the effects of robustoxin, the lethal neurotoxin from the Sydney funnel-web spider Atrax robustus, on sodium channel activation and inactivation. Pflügers Archiv European Journal of Physiology.]() 8. [Pallaghy et al. (1997). Solution structure of robustoxin, the lethal neurotoxin from the funnel-web spider Atrax robustus. FEBS Letters.]() 9. [Nicholson et al. (1996). Selective alteration of sodium channel gating by Australian funnel-web spider toxins. Toxicon.]() 10. [Herzig et al. (2020). Australian funnel-web spiders evolved human-lethal δ-hexatoxins for defense against vertebrate predators. Proceedings of the National Academy of Sciences.]() *Published September 1, 2026. 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