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Rare native spiders fostered by Bristol Zoo Gardens released into the wild - September 2012

After ten weeks of careful husbandry at Bristol Zoo, 172 tiny fen raft spiderlings (Dolomedes plantarius) are set to be released into the wild.

The young spideBristol Zoo keeper with Fen Raft spiderlingrs have been raised by keepers at Bristol Zoo as part of a conservationrearing project to help save this native species, which is one of Europe's largest but least common spiders.

The spiders are so rare that they are protected by law in the UK and have been classified as ‘Vulnerable’ on theInternational Union for Conservation of Nature(IUCN) Red List of Threatened Species. They are only found in three sites in Britain – Norfolk, East Sussexand South Wales.

The 12 week old spiderlings, which were just two millimetres in size when they arrived, received intensive care by experts in Bristol Zoo’s Bug World - a process that took several hours every day and included being hand-fed flies.

Carmen Solan, invertebrate keeper at Bristol Zoo said:They have grown from tiny dots to 4-5mm long. It’s been an amazing project to have been involved in, we’re rather sad to see them go! ”

Mark Bushell, Assistant Curator of Invertebrates at the Zoo, added: “The aim was to give these little spiders the best possible start in life, which is something we’re very proud to have achieved. The spiders leaving us are healthy and strong, well equipped for a life in the wild.”

The young spiders will be released into wild fenland habitats in Norfolk to begin their adult lives. These semi-aquatic spiders can grow to approximately 7cm in leg span and live for around three years.

The Fen Raft Spider Species Recovery programme is a partnership led by Natural England to safeguard the future of this species, which is under threat from habitat destruction and drying out of their marshland homes.

Natural England’s head of profession for biodiversity, Dr Peter Brotherton said: “The spiders from the first release in 2010 are just starting to breed this year – this is an important milestone for the recovery programme and a clear indication we’re going in the right direction. If this species is to recover it still needs more help and the dedicated support from organisations such as Bristol Zoo is vital to the future of our biggest spider.”

Bristol Zoo Gardens is a conservation and education charity and relies on the generous support of the public not only to fund its important work in the Zoo, but also its vital conservation and research projects spanning five continents.

For more information about visiting Bristol Zoo Gardens, visit the website at phone 0117 974 7300.


Notes to the Editor:

About Fen Raft Spiders

  • The fen raft spider (Dolomedes plantarius) is one of the UK’s rarest, largest and most spectacular spiders.
  • The spiders can walk on water and hunt for prey both at the water surface and underwater. They feed on a wide range of wetland invertebrates and can also take small amphibians and fish.
  • The adult females can lay in excess of 700 eggs into a beautiful silk sac which they carry in their mouths for at least three weeks until the tiny spiderlings emerge.
  • Although they don’t spin webs to catch their prey, they care for their young in a large tent-like nursery webs built in vegetation above the water. 
  • The spiders usually take two years to mature: once adult, the females can produce two egg sacs during the summer but dies before winter.
  • This species was first discovered in the UK at Redgrave & Lopham Fen National Nature Reserve at the source of the river Waveney, in East Anglia, in 1956. This relatively recent discovery almost certainly results from earlier confusion with the very similar but more common raft spider species Dolomedes fimbriatus.
  • Since 1956 it has been found at just two other sites – in East Sussex and in South Wales. This is a wetland species depending on a reliable, year-round supply of unpolluted water. It is usually found in fens and grazing marsh ditches. These habitats have declined in extent and quality and this almost certainly accounts for the spiders rarity and fragmented distribution. At Redgrave & Lopham Fen the spider population was reduced to very low levels by artesian abstraction which desiccated the site. Although the fen has now been restored, the spider population there remains very small and fragmented.
  • The England Biodiversity Strategy commits a landscape scale approach to conservation so that “we will see an overall improvement in the status of our wildlife and will have prevented further human-induced extinctions of known threatened species” by 2020.  The Strategy acknowledges that some species will need specifically tailored action and fen raft spiders (one of only two British spiders to be fully protected by law) are listed as “requiring special help if they are to recover and thrive again in England”

The Fen raft spider translocation programme

  • To secure the future of this species both at this site and nationally, new populations are being established in suitably restored habitat. The Biological Action Plan target is to increase the number of UK populations from 3 to 12 by 2020.
  • Translocations began in 2010 and 2011 using grazing marsh habitat on Suffolk Wildlife Trust nature reserves on the river Waveney, downstream from Redgrave & Lopham Fen.
  • The releases were of tiny spiderlings. Some of these spiders are expected to breed for the first time in summer 2012.
  • The spiders used for translocation were obtained from a Sussex Wildlife Trust nature reserve and bear-by sites, and from Redgrave & Lopham Fen. Using spiders from both sites maximises genetic variation and increases the chances of the new populations adapting to their new homes and to climate change.
  • The Sussex population is large are so small numbers of female spiders can be removed and released with their broods of spiderlings.
  • Because the Redgrave and Lopham Fen population is very small, spiderlings are reared in captivity for three months before release, increasing to over 90% their slim survival chances in the wild. Some of them are released back on the Fen, so that the population there is not depleted, while others go to the new sites.
  • The tiny spiderlings have to be kept and fed in individual test tubes to prevent them eating each other! This very labour-intensive work is being undertaken by a network of ‘foster parents’ which, in 2012, includes 11 BIAZA zoos.
  • In 2011 almost 10,000 spiderlings were released at the new sites. In 2012 more spiderlings will be released at some of these sites and one more new population will be established in the Broadland.
  • The fen raft spider translocation programme is a partnership between Natural England, the Suffolk and Sussex Wildlife Trusts, The Broads Authority, the RSPB, BIAZA and the BBC Wildlife Fund.
  • More information about fen raft spiders and their conservation can be found at

About the partner organisations

Bristol Zoo Gardens

  • Bristol Zoo Gardens is a conservation and education charity and relies on income from visitors and supporters to continue its important work. 
  • Bristol Zoo is involved with more than 100 co-ordinated breeding programmes for threatened wildlife species. 
  • Itemploys over 150 full and part-time staff to care for the animals and run a successful visitor attraction to support its conservation and education work. 
  • Bristol Zoo supports – through finance and skill sharing - 15 projects in the UK and abroad that conserveand protectsome of the world’s most endangered species.
  • In 2011 Bristol Zoo celebrated its 175th birthday. Over that past 175 years, the Zoo has brought six generations of Bristolians closer to wildlife, helped save over 175 species from extinction, established over 30 field conservation and research programmes all over the world, showed 40 millionschool-aged children the wonder of nature and given more than 90 million visitors a wonderful day out.
  • In 2010 Bristol Zoo Gardens set up a Conservation Fund to raise vital funds to help care for threatened animals and plants – both in the Zoo and through the conservation work we do in the UK and around the world.
  • Bristol Zoo Gardens is a member of the British and Irish Association of Zoos and Aquariums. BIAZA represents more than 90 member collections and promotes the values of good zoos and aquariums.

Natural England

  • Natural England is the government's independent adviser on the natural environment. Established in 2006 our work is focused on enhancing England's wildlife and landscapes and maximising the benefits they bring to the public.
  • We establish and care for England's main wildlife and geological sites, ensuring that over 4,000 National Nature Reserves and Sites of Special Scientific Interest are looked after and improved.
  • We work to ensure that England’s landscapes are effectively protected, designating England’s National Parks and Areas of Outstanding Natural Beauty, and advising widely on their conservation.
  • We run Environmental Stewardship and other green farming schemes that deliver over £400 million a year to farmers and landowners, enabling them to enhance the natural environment across two thirds of England's farmland.
  • We fund, manage, and provide scientific expertise for hundreds of conservation projects each year, improving the prospects for thousands of England's species and habitats.
  • We promote access to the wider countryside, helping establish National Trails and coastal trails and ensuring that the public can enjoy and benefit from them.
  • Natural England has been supporting different elements of fen raft spider conservation since 1991 through its Species Recovery Programme.


BIAZA (The British and Irish Association of Zoos and Aquariums) has joined the fen raft spider project as part of their remit to conserve native species throughout Britain and Ireland through the joint efforts of the zoo community. Zoos play an important role in the conservation of native species through carefully managed breeding programmes, fundraising and provision of animal health expertise. Additionally, more than 25 million people visit BIAZA zoos every year, which puts them in a unique position to inform a wide and diverse audience about the plight of threatened species. 

Suffolk Wildlife Trust

The expertise of our staff and volunteers gives Suffolk Wildlife Trust an unrivalled understanding of the county's natural world.  With this local focus, we are able to safeguard habitats and species, taking action on the ground, where it really counts.  Our aim is to create a Living Landscape where wildlife flourishes in our countryside, towns and villages.  Our conservation advisors work with farmers and local communities to improve their land for wildlife and create networks of linked up habitat across Suffolk.  We care for over 6500 acres of Suffolk's most precious wildlife habitat in over 50 nature reserves which are tranquil havens for everyone to enjoy.  Action for local wildlife, led by local people has always been Suffolk Wildlife Trust's great strength. Our vision for a Living Landscape for Suffolk, is a 21st century approach to nature conservation firmly grounded in our ethos of enabling people to take action for wildlife where they live. 

Sussex Wildlife Trust

Sussex Wildlife Trust is the leading conservation organisation covering Brighton & Hove, East and West Sussex.  Sussex Wildlife Trust looks after over 4500 acres of downland, woodland, wetland and heath. Our work also includes environmental education, working with land owners, companies and local communities to conserve Sussex.  We are supported by over 33,000 members which is almost 3% of the population of Sussex. We are one of 47 local Wildlife Trusts in the UK. 

Broads Authority

The Broads Authority is a statutory body with a duty to manage the Norfolk and Suffolk Broads. The Authority has three core purposes:

  • conserving and enhancing the natural beauty, wildlife and cultural heritage of the Broads;
  • promoting opportunities for the understanding and enjoyment of the Broads by the public; and
  • protecting the interests of navigation.

It must also consider the needs of agriculture and forestry, and the economic and social interests of those who live and work in the Broads. The Authority has 21 members appointed from local councils and by the Secretary of State for the Environment and navigation interests. They make decisions and consult on the management of the Broads at six members' meetings a year. A Broads Forum, with members representing a wide range of interested parties, is consulted on key issues.


The RSPB speaks out for wildlife, tackling the problems that threaten our environment. Wildlife and the environment face many threats. Our work is focussed on the species and habitats that are in the greatest danger. Our work is driven by the passionate belief that birds and wildlife enrich people's lives. We have more than one million members, over 13,500 volunteers, 1,300 staff, more than 200 nature reserves, 10 regional offices, four country offices... and one vision - to work for a better environment rich in birds and wildlife.

BBC Wildlife Fund

The BBC Wildlife Fund helped to fund the fen raft spider translocation project between 2009 and 2012. Recently wound-up, its core purpose was to raise awareness and funds to save threatened wildlife and places. The fund offered a unique opportunity to capitalise on the creative skills of the BBC enabling wider audiences to engage in the plight of wildlife.