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| Fen raft spider (Dolomedes plantarius) hunt prey by skating across the water |
If you thought your garden was free from lurking predators, think again—especially if you live near a fen.
The UK is witnessing a remarkable resurgence of the giant fen raft spider, a rare and fearsome arachnid that is once again thriving in its wetland habitats.
The Return of the Fen Raft Spider
These chunky spiders are not your average garden dwellers. Found along the edges of ponds, fens, and coastal grazing marshes, fen raft spiders use their front legs to detect vibrations on the water’s surface.
But don’t mistake their stillness for inactivity—they are patiently waiting for their next meal, which often includes fish and tadpoles. Yes, you read that right.
These spiders can even glide across the water to snatch their prey, a skill that is as terrifying as it is impressive.
A Rare and Massive Arachnid
Fen raft spiders are among the largest and rarest arachnid species in Britain.
With bodies measuring up to 22mm (0.87 inches) and a leg span reaching 70mm (2.8 inches), females are roughly the size of a human palm.
Spotting one in your home would require more than a quick mug capture; these are no ordinary spiders.
However, despite their imposing size, these spiders have been on the brink of extinction.
The destruction of their wetland habitats due to human activity nearly wiped them out by 2010.
They were listed as endangered on the UK Red List in 1991 and are protected by the Wildlife and Countryside Act (1981).
A Conservation Success Story
Thanks to dedicated conservation efforts, the fen raft spider is returning.
In Norfolk and Suffolk, their numbers are rising, with around 3,750 individuals now skittering around Strumpshaw Fen in Norfolk.
Conservationists have successfully increased the number of sustainable populations from three in 2011 to 12 today by creating more suitable habitats and relocating spiders.
A Boon for Wildlife, But Not for Arachnophobes
While the news might send shivers down the spine of anyone with arachnophobia, it’s a triumph for local wildlife.
“The females are impressive in size, but also beautiful—they are truly special to see,” said Tim Strudwick, RSPB Mid Yare nature reserves site manager.
He reassured the public that despite their size, these spiders are harmless to humans.
The spiders are shy and mostly found in grazing marsh ditches, making them difficult to spot.
However, from June to September, visitors to Strumpshaw Fen have the best chance to see the mature females and their nursery webs, which can stretch up to 25cm across—the size of a pizza.
Still Vulnerable
Despite their recent success, fen raft spiders are still classified as vulnerable.
Their future remains uncertain, dependent on continued conservation efforts and protection of their wetland habitats.
For now, though, these semi-aquatic spiders are a testament to the power of conservation and the resilience of nature.
So, if you’re out for a stroll near a fen, keep an eye out—you might just spot one of Britain’s largest and most extraordinary spiders lurking by the water’s edge.