Queen of the Marsh: The Fen Raft Spider
By Kerry Williams
Communications Officer - Conservation
Fen Raft Spiders are totally badass. One of the UK’s biggest arachnids, adult females can reach body lengths of 23mm, and 7cm including their legs. And like many strong women, they get a hard time of it in the media. Despite their imposing image, these spiders are shy, gentle, and completely harmless to humans. To invertebrates, small fish, and amphibians, on the other hand, they are a force to be reckoned with.
Living a semi-aquatic lifestyle, the Fen Raft hunts on water. Although they do make webs as nurseries to house their spiderlings (yes, spiderlings, tell me that isn’t cute), they don’t use webs for capturing their prey. Instead, they exercise extraordinary ambush tactics.
Much like many of us at this time of year, the spider’s legs are covered in fine, water-repellent hairs. With its back legs on the water's edge vegetation, the spider rests its forelegs on the surface of the water, sensing vibrations of oncoming prey. Distance, direction and strength of movement can all be calculated, and not just in the water; this finely tuned system can even sense motion through the air. Once the unsuspecting soul is in reach, the spider pounces, immobilising its quarry with a venomous bite.
Although spiderlings can be vulnerable, few predators exist for the adult spiders, aside from humans and the occasional daring Heron. However, if threatened, the water-resistant hairs allow the spider to literally run on water to escape. Alternatively, it can break the surface to hide or pursue prey by shimmying down underwater plant stems.
It’s not all action thriller power moves. The species has suffered significant historical decline due to a multitude of threats, including climate change, pollution, and loss of their precious wetland habitat, either through water abstraction (removal for human water supply), or destruction.
Enter Pevensey Marshes. With a myriad of wiggly ditches, strong-stemmed vegetation, and marsh for days, the wetland is a Fen Raft-ian paradise. As it has done in previous wetland projects, such as those of Suffolk Wildlife Trust, the spider is thriving here, and overall population numbers are on the up.
Working closely with local landowners, the project is one not just of nature recovery, but of collaboration, and this engagement is exactly what we need to benefit the Fen Raft Spider and its hopeful longevity. Increasing personal natural connections can help to alleviate the vilification of many of our amazing, yet maligned, UK species, including spiders. With our support, we hope the Fen Raft Spider continues to flourish as a vital player in this wetland ecosystem.
Comments
So pleased about this – I’m no arachnologist, but I do have a fascination for spiders and it’s great news that their numbers are increasing at Pevensey. How about Saltidae? Are there any significant colonies of these in East Sussex? I love jumping spiders they seem to have personalities! Forgive me I know this is just blatant anthropomorphism!
07 Nov 2024 11:56:00
Sussex Wildlife Trust:
There are numbers of jumping spiders in Sussex, particularly Zebra Spiders: https://www.wildlifetrusts.org... I don't blame you, they are very cute!
Thank you, Kerry. I much enjoyed this (and liked the comment about our legs being hairy at this time of year – not me, I’m glad to say!). My sister-in-law lives near Pevensey, so I hope I might see the spider when I next visit.
07 Nov 2024 12:05:00
Very interesting beasty. The article shows the vulnerability of such species to habitat loss and the importance of protecting the environment.
07 Nov 2024 12:11:00
Thank you for mentioning the local landowners, whose livestock graze the Levels! Ruminant livestock are so important for maintaining habitats, yet they belch carbon dioxide, and we’re told to get rid of them and give up red meat and milk – perhaps the SWT can explore the difficult dilemmas we all have to face, and the influences our choices have on the countryside. It’s complicated, that’s for sure!
07 Nov 2024 12:22:00
I wish people weren’t so insanely scared of spiders. We need to do more to let people understand them more, thank you for what you do x
07 Nov 2024 12:24:00
Brilliant. Thank you all for improving their environment on the marches. 👍🤗
07 Nov 2024 12:54:00
Thank you Kerry! Really enjoyed this.
07 Nov 2024 13:59:00
I wish I wasn’t scared of spiders and could just feel pure admiration and awe without the tinge of terror. I have to admit when I saw this in the national press (“spiders the size of your hand!”) a shiver went down my spine. But you’re right, they are really badass and beautiful too. I will keep trying to get over my fear and be glad they’re making a home so close to me.
07 Nov 2024 14:52:00
What a beautiful picture of the spider. I’m so glad to know that it’s thriving in Pevensy marshes. We’ve recently had a new wetlands established in Lewes, which has been immediately claimed by a variety of water birds and other creatures. I wonder if the raft spider has found it?
07 Nov 2024 15:25:00
Sussex Wildlife Trust:
We don't know if there have been any sightings of the spider at the new Lewes wetland - you can keep an eye on project updates through their website and social media!
I’m usually a bit of an arachnophobe but I have to say the Fen Raft Spider may just be nudging me towards a change of heart. Having said that I’m still not keen on those big b***gers that suddenly scuttle across the floor as you’re watching TV – ha ha
07 Nov 2024 18:14:00
Long live spiders.
Delighted that Pevensey marshes are giving a good home to the Fen Raft Spider. She looks beautiful
07 Nov 2024 19:40:00
Hi, I’m a bit confused with my last notification email from SWT. This one mentions Raft Spiders, one animal I would love to see. Especially when you use words like ‘come and see’ but when I go onto Pevensey Marshes reserve sight it says ‘not open to the public. Could you please advise if we can visit the area in late November and see these amazing spiders. Kind regards Vince
07 Nov 2024 20:06:00
Sussex Wildlife Trust:
That's correct, Pevensey Marshes is one of the few SWT reserves closed to the public. This is to ensure lack of disturbance to wildlife, which is supporting the success of the species there.
Wonderful to meet this fantastic Fen Marsh spider. So clever! Amazing legs balancing on the water. Beautiful body colour; it’s been lovely to learn about it!
07 Nov 2024 22:23:00
Very interesting and informative
08 Nov 2024 08:51:00
Perhaps you could do something to counteract the ridiculous scare-mongering stories and headlines that pop up on my phone (no tech skills or internet I am in the library) stating that spiders the size of your hand have been released and hinting that they are ‘roaming the streets’.
08 Nov 2024 14:04:00
Sussex Wildlife Trust:
You're right that the Fen Raft Spider has had some incorrect and sensationalist media coverage. We hope more positive articles like this one do counteract them, and show how these spiders are not to be feared.
Good to read and it would be great to hear more about Pevensey Marshes. Some activities in this area would also be very welcome.
08 Nov 2024 17:35:00
Thanks Kerry for this interesting and informative article. Articles like this should also be sent to Local Press to counteract the false sensationalist stories which create false image about spiders.
08 Nov 2024 20:46:00
So interesting to read about this wonderful species, and great to hear that they are thriving in the area. Thank you for the article and for doing so much to encourage these spiders and preserve their wetland habitats.
10 Nov 2024 14:10:00
I was fortunate enough to be part of a Trust visit this reserve a few years ago. The spider really is quite remarkable and I was also introduced to Tubular Water-dropwort, a beautiful plant
11 Nov 2024 16:55:00
An informative read. Thank you.
11 Nov 2024 20:21:00
A heartening read! Wonderful to hear of the collaboration with the local landowners to help the Fen Raft Spider! Thankyou.
17 Nov 2024 09:14:00
Very enjoyable and informative article Kerry. In celebration of hairy legs!
27 Nov 2024 10:40:00
I’m an arachnophobe, but getting better! These spiders are products of nature (as are humans!) and as – often irresponsible – ‘custodians’ of the earth, we should help protect all living things. Glad I became a member!
25 Feb 2025 08:02:00
Sussex Wildlife Trust:
So glad to hear. Thank you. We will share with the membership team!
Interesting article. Best of luck to the fen raft spider!
04 Apr 2026 11:54:00