News
Over a thousand rare spiders released on Suffolk Broads
21st October 2010
After being nurtured in a cosy kitchen since the spring, 1600 rare spiderlings are being released at Castle Marshes between Lowestoft and Beccles. The work, grant aided by BBC Wildlife Fund, is a Natural England/Suffolk Wildlife Project led by Dr Helen Smith.
The spiderlings of the fen raft spider Dolomedes plantarius are being released into suitable dykes at Castle Marshes. The tiny 4mm spiders which are perfect replicas of the 23mm (female body length) adult complete with go-faster stripes, are hybrids between Pevensey Levels and Redgrave and Lopham populations.
Helen has been hand rearing thousands of the spiderlings at home in her kitchen for the last four months. “I mated the parents from Pevensey and Redgrave populations in the spring and reared around 100 offspring from each brood,” says Helen who has been up until 2am on many occasions, 7 days a week, diligently feeding flies to the young. The surplus spiderlings from the broods were reared at the John Innes Centre in Norwich.
When Helen established that there didn’t appear to be any deleterious affects of hybridisation, she sought Natural England’s approval for release. “The hybrids bring the advantage of increased genetic variability to the new population. This combined with the use of Pevensey stock, from almost identical habitat in Sussex, should give the new population at Castle Marshes the best potential to adapt to its surroundings and to cope with the impacts of climate change.”
Castle Marshes on the River Waveney, approx 50km downstream from Redgrave and Lopham Fen, will be the first new site for the fen raft spider in East Anglia. Site preparation for establishment of the new spiders included enhancing the ditch network. Another translocated population was released simultaneously into recently created pools at Redgrave and Lopham Fen NNR which is already well known for its resident natural population (one of only 3 in the UK). “Castle Marshes has always been our first target for a new site in East Anglia because of the ideal habitat, the fact that it is on the same river as Redgrave and Lopham Fen and the huge enthusiasm of the SWT voluntary wardens,” says Helen.
An exhibition of work resulting from a fen raft spider artist residency with Sheila Tilmouth and based at SWT’s Carlton Marshes centre, will coincide with the release running from 25-28 October. Post translocation genetic monitoring will be carried out in collaboration with local SWT volunteers and the Nottingham University spider lab.
ENDS
Notes to editors
Dolomedes plantarius was not discovered in the UK until 1956 when eminent arachnologist Eric Duffey found it around the margins of peat pools at Redgrave and Lopham Fen, at the source of the River Waveney on the Norfolk/Suffolk border. A second UK population was discovered, 180 km away, when Peter Kirby identified D. plantarius from grazing marsh ditches on the Pevensey Levels in East Sussex in 1988. In 2003, a third UK population was discovered on a disused canal near Swansea, South Wales, by local naturalist Mike Clark. The fen raft spider is one of only two British spiders that if fully protected by law and has been the subject of a Species Recovery Programme since 1999.
Photographs: Header - Fen raft spiders courting in the kitchen by Helen Smith, image right - Spider release at Castle Marshes by Audrey Boyle, image left - Helen Smith and Matt Gooch during release by Audrey Boyle.
