Bringing the UK’s largest spider back from the brink - Chester Zoo

We’ve played a major role in a project to save the fen raft spider from extinction.

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.

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.