Why getting bitten by a Sydney funnel-web spider isn’t the end of the world

The thought of being bitten by one of the deadliest spiders on Earth, the Sydney funnel-web, is sure to send a shiver down your spine. But when you unpick the web of information around these amazing arachnids, you’ll find that, actually, it wouldn’t be the end of the world.

In a podcast episode of Cosmos Would You Rather, I argued that a bite from a Sydney funnel-web is much preferable than one from an eastern brown snake – and here’s more about why.

Meet the Sydney funnel-web spider

In total there are about 40 species of funnel-web spiders in Australia, all of which are found in the eastern states. But the one we’re interested in is the Sydney funnel-web (Atrax robustus), the species likely responsible for all 13 recorded deaths from funnel-web spiders in this country.

A medium to large spider, with a body length that ranges from 1-5 centimetres, they’re known for their hairless, glossy, dark carapace that ranges in colour from black to brown.

They’re only found within a limited range in New South Wales, usually within about a 100 kilometre radius of Sydney – from Newcastle to Nowra and as far west as Lithgow.

A map showing the distribution range of sydney funnel-web spiders in red.
Distribution map of Sydney funnel-web spiders (Atrax robustus). Credit: NordNordWest, Creative Commons by-sa-3.0 de

And as you might expect from the name, these critters spin incredible funnel-shaped burrows to trap their prey. Distinctive and irregular spider silk trip-lines radiate out from the entrance, working to alert them to possible prey, mates, or danger on their doorstep.

But while Sydney funnel-web spiders might have an infamous reputation for being an aggressive species, Olivia Christmas from Taronga Zoo in New South Wales told Cosmos that they’re really a defensive species.

“I really don’t like that word aggressive because it makes you think that that if you see that spider it’s going to chase after you. If I was to put one on the ground right now and open up the lid, it’s not going to rush towards you to bite you.

“The key difference is that they hold their ground. They have this incredible threat display before they bite; they raise up on their rear legs, and they’ve even got this red patch on their bellies.

“So, with our spiders at least, they have to be really worked up and agitated before they start producing that venom.”

Sydney funnel-web spider in defensive pose
Sydney Funnel-Web Spider in defensive pose. Credit: Ken Griffiths/Getty Images

Their bites pack a punch, but not all of them

According to Christmas, females can live for up to 20 years, but males only manage a couple of years.

“Every summer when the rains come out, the ground is wet, and it’s breeding season, males leave their burrows and they go wandering on a search for a female,” she says. “So that’s why [you’re] more likely to get bitten by a male, because they’re the ones that are leaving the safety of their borrows.”

In all fatalities, where the gender of the spider was confirmed, a male Sydney funnel-web spider was responsible.

This is because their venom is five times more toxic than the females and it’s all thanks to a single component – Delta atracotoxin. This single peptide, out of all other molecules that make up the venom, is the one deadly to humans.

It’s a neurotoxin that severely effects the nervous systems of primates, but not other animals, causing the spontaneous and repetitive firing of nerves.

3d stick model of delta-atracotoxin
3d stick model of delta-atracotoxin-Ar1 (robustoxin) from male Sydney funnel-web spider (Atrax robustus). Credit: Ayacop via Wikimedia Commons, adapted from Alewood et al., 2003, DOI: 10.1021/bi030091n.

A 2005 review of recorded clinical cases found that only 17% of Sydney funnel-web spider bites resulted in severe envenoming, with 42% of those occurring in children.

When it does occur symptoms develop early with tingling around the lips, a twitching tongue, profuse salivation, tears, sweating and muscle spasms.

If left untreated, this can develop into high blood pressure, rapid heartbeat, respiratory distress, fluid in the lungs, and can lead to death within an hour,  and in as little as 15 minutes for children with their lower body weight.

But while this all sounds a tad alarming; it might comfort you to know that there have been no fatalities from a Sydney funnel-web since the antivenom was developed in the 1980s.   

How do you make the antivenom?

Developed in 1980 by Dr Struan Sutherland, and introduced clinically in 1981, the Sydney funnel-web spider antivenom has since been proven effective in treating bites, including from a variety of other species of funnel-web.

The Australian Reptile Park’s funnel-web spider antivenom program began in 1981, playing an important role in the invention of the antivenom and providing the raw venom to CSL Seqiris in Melbourne for production.

During the process they encourage the spider to raise up onto its rear legs, expose its fangs, and start producing venom. Then, they come along with a tiny little pipette attached to a very low powered vacuum, and they vacuum the tiny venom droplets right off of the fangs.

It takes about 150 of these milkings to produce enough venom to be turned into one vial of antivenom.

Then, to turn that venom into antivenom, it’s freeze dried and sent off to Seqiris, which dilutes it and inject it into rabbits to trigger an immune response. By increasing the dosage in small increments over the course of 6 six months, the rabbit builds up a tolerance and can eventually withstand six-times the lethal dose.

At this point, blood is extracted and spun in a centrifuge to separate out the antibodies to make the antivenom. When administered after a bite, these antibodies bind to the different components of the venom in our circulation – including the deadly neurotoxin Delta atracotoxin – neutralising their activity.

So, what do you do if you’re bitten?

The good news is, thanks to the limited range in which these spiders live, if you get bitten, you’ll be in an urban environment where you can seek medical assistance by calling 000 and receive treatment quickly.

Like with snake bites, first aid for a Sydney funnel-web spider bite is the pressure immobilisation technique (PIT), which slows down the flow of lymphatic fluid through which the venom gains access to the circulation.

This means keeping the person as still as possible, lying down if possible, and applying a firm bandage over the bitten area. A limb should be bandaged entirely – fingers to shoulder or toes to hip – and as tightly as you would bandage a sprained ankle. If possible, apply a rigid splint to stop the limb from moving and keep still to wait for an ambulance or transport to the nearest hospital.

It’s always important to know what to do if you ever find yourself in this situation, but Christmas says that while these animals do share our spaces, they’re not something to be feared.

“Give them the respect that they deserve, and give them their space, and you’re not going to get bitten really unless you’re extremely unlucky or you’re going out of your way to disturb them,” she concludes.

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