November 28 2014 Latest news:
Wednesday, March 5, 2014
A programme to boost numbers of the threatened fen raft spider has seen their numbers grow dramatically, Broads bosses have revealed.
The fen raft spider, or the great raft spider, is a European species of spider in the Pisauridae family.
It’s full name is Dolomedes plantarius.
Like other spiders of its kind, it is semi-aquatic, hunting its prey on the surface of the water, although it can adapt to being on land and being underwater.
The fen raft spider uses the water’s surface how other spiders use webs – its short, velvety, water-repelling hairs allow it to walk on water.
The fen raft spider is a large species within its range.
Adult females can have bodies of over 20mm in length, with a span of 70mm including their legs.
Typically the spider is black or brown with white or cream stripes on the sides of its body.
The great raft spider is predatory and waits at the water’s edge to hunt for its prey.
Its diet consists of aquatic invertebrates such as pond skaters and dragonfly larvae.
However, it has been known to catch small vertebrates such as sticklebacks and tadpoles.
The fen raft spider is also commonly considered to be beautiful by spider lovers – a view with which many disagree!
At a Broads Biodiversity and Water Forum organised by the Broads Authority, Dr Helen Smith, who co-ordinates the project for Natural England and Suffolk Wildlife Trust, revealed that over 20,000 fen raft spiders have been released into new homes.
The fen raft spider – Britain’s biggest variety – has only been found on three wetland sites in the UK, one of which is Suffolk Wildlife Trust’s Redgrave and Lopham Fen nature reserve, near Diss, where they were discovered in 1956.
The other sites are the Pevensey Levels in Sussex and Pant-y-Sais National Nature Reserve in Swansea. Dr Smith, who raised the spiders in her own kitchen, said the species’ survival has been threatened by a “loss of wetlands, water and water quality”, as well as the potential threat of salinisation following the December storms.
The recovery programme, which began in 2010, is supported by a grant from BBC Wildlife.
Ecologist Dr Smith researched more suitable homes for the spiders.Using criteria including the site’s hydrological security, its future management, size and provision of nearby enthusiastic volunteers, two sites on the lower River Waveney and an RSPB mid-Yare reserve in the Norfolk Broads were picked as new homes.
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Dr Smith raised the spiders in individual test tubes, a technique devised with the John Innes Centre in Norwich, and fed them on fruit flies.
She estimates that around 5,800 spiderlings have been released at the sites and that a further 31 nursery webs could mean 15,000 more baby spiders have been born in their new homes since 2010.
Two thousand more have been released into Redgrave and Lopham Fen which had seen its numbers decline. Dr Smith said: “I think it is early days but we are on the road to re-establishing these spiders for people to enjoy in the Broads on a day out. People can expect to go out on the Broads, see and enjoy them.”
Dr Smith said: “In the future we will continue to monitor existing populations, search for overlooked populations, monitor new ones, establish more and feed back our methods to the translocation project.” The plight of the wetland spider has even attracted the attention of the arts world after Yorkshire artist Sheila Tilmouth was granted permission by Arts Council England in 2009 to work alongside the spider at Redgrave and Lopham Fen.
Do you think it is important to keep rare spider species alive? Write, giving full contact details, to Letters Editor, Prospect House, Rouen Road, Norwich NR1 1RE.