UK's largest spider the size of a rat sees huge population boom in Britain

The Fen Raft Spider is making a comeback, thanks to conservation efforts.
-Credit: (Image: Helen Smith/RSPB)


Spiders the size of rats are thriving in the UK, thanks to help from experts at Chester Zoo. The population of the fen raft spider - Britain's largest eight-legged creature - is booming across the nation.

It comes after near-extinction 15 years ago, brought about by the destruction of the unique species natural wetland habitat. But back in 2011, experts at Chester Zoo set about saving the giant spider species - which can grow to the size of an adult human palm - by hand rearing them in test tubes before releasing them.

Experts say they are now thriving once again in the UK, with an estimated 10,000 breeding females across the country - their best year on record.

A spokesman for Chester Zoo said: "While they may look big and scary to some, the fen raft spider is harmless and plays a vital role within healthy aquatic ecosystems. However, 15 years ago, they almost became extinct after people destroyed its wetland home.

"To help save this unique species, back in 2011, our experts set about rearing hundreds of baby spiders in individual test tubes (so they didn’t eat each other!) as part of a collaborative conservation breeding rescue programme in partnership with the RSPB.

"Our team delicately hand fed tiny flies to each of the hundreds of spiderlings using tweezers, day in, day out, for weeks on end in our bio-secure breeding facility. Eventually, the young spiders grew strong enough to be returned to their natural habitat , which our partners worked to restore, and we released them in their hundreds.

"Now, almost a decade and a half later, our friends at the RSPB estimate there are 10,000 breeding females across the UK , and they’re having their best year on record.

"We’re so proud of the part we’ve played in this incredible conservation success story, ensuring the survival of a species that was previously on the brink of extinction."

Tim Strudwick, RSPB Mid Yare nature reserves site manager, said: "These spiders have an important role in maintaining the rich aquatic diversity found in the grazing ditches on our reserves. The females are impressive in size, but also beautiful – they are truly special to see.”

Despite their large size, fen raft spiders are completely harmless to humans . They can grow to be around the size of an adult human palm, and can be identified by an eye-catching white stripe that runs along their body.

As a semi-aquatic hunter they play an important role maintaining the marsh ecosystems they are most commonly found in. Unlike most spiders which hunt by capturing prey in webs, this efficient predator lies in wait with its front legs resting on a body of water. Tiny hairs on their legs (called trichobothria) detect vibrations in the water made by prey, allowing them to quickly pounce.

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