Print page

UK's largest spider is making a comeback; but don't worry- it prefers fens to fireplaces!

Last modified: 31 October 2015

Fen raft spider

fen raft spider

Image: Helen Smith

Far from the giant house spiders seeking dark spaces and crevices behind the fireplace this Halloween, the semi-aquatic fen raft spider prefers to make its home in fens and marsh ditches.

Thanks to a highly successful translocation project, the rare spiders are now thriving on RSPB land close to Strumpshaw Fen in the Norfolk Broads.

With over 480 nursery webs counted this season (July-October), compared with 184 in 2014, this new population puts the spider in a much more secure position as a UK species. 

Tim Strudwick, RSPB Site Manager at Strumpshaw Fen nature reserve, said: "It is fantastic to see the spiders now thriving on the reserve, having been first released in 2012".

"The spiders are doing so well due to the excellent condition of the habitat and our management of the grazing marshes is maintaining ideal conditions for them. They have exactly the right vegetation mix along the ditches to support their nursery webs and the richness of invertebrate prey that the spiders need."

"It is great to see the spiders are responding by extending their range into new ditches."

Unlike our eight-legged friends you may find lurking underneath the sofa this autumn, these water-walking giants can be found living in ditches and pools in chalky wetlands.

The fen raft spider is a striking creature with a dark body and cream stripes down the side; they are very large and females can sometimes reach up to the size of the palm of a hand.

Up until 2010 there were only three known populations in the UK, leaving the species very vulnerable and at real risk of extinction.

A pioneering translocation project between conservation partners and funders- including Suffolk and Sussex Wildlife Trusts, Natural England, the Broads Authority, the RSPB and the British Arachnological Society- has already substantially reduced this risk by establishing new fen raft spider populations in the Broads. 

Unlike most invertebrates, it is easy to monitor the population through their enchanting, crystal-like nursery webs in which they raise their young. This year has seen an increase in the number of webs at all of the sites where the spiders were released.

Over a thousand nurseries have been counted at one of the new sites - a Suffolk Wildlife Trust nature reserve - where tiny spiderlings were first released just five years ago. The spiders have also spread from the 500m stretch of ditch where they were released to occupy over 3km of ditches within the reserve. 

The project has been co-ordinated by Dr Helen Smith, an ecologist contracted by Natural England under the Species Recovery Project. She said: “These large and beautiful spiders have really made these new sites home. This is a species that is clearly able to thrive in the Broadland grazing marshes that have been so carefully restored by conservation organisations in recent years. It's already made a great start on colonising the area's extensive ditch networks and, in the process, has taken a big step back from the brink.”

Other RSPB reserves across the country are also home to some fascinating rare spider species. Clubiona genevensis, which can be found on the RSPB’s Ramsey Island, is one of the UK’s smallest and rarest critters. This tiny island resident is orange-yellow in colour and measures just 3 mm in length. 

Ladybird spiders, named after their distinctive bright red and black markings on the mature males, were thought to be extinct until rediscovered at one site in Dorset at the end of the last century. The RSPB has been working with experts in another ground-breaking reintroduction programme by providing a home for them at Arne nature reserve in Dorset. New evidence has shown that they have bred and are gradually spreading their range.

Visit one of our nature reserves this Halloween and discover the magic of wildlife. As well as beautiful birds, you'll find fascinating flowers, intriguing invertebrates, delicate damselflies and marvellous mammals.

How you can help

RSPB reserves are great places for a day out

Nature reserves

Share this