ZSL London Zoo fosters endangered baby spiders

© Dave Clarke/ZSL

Fen raft spiders (Dolomedes plantarius) have only been found at three sites in the UK and are listed as a vulnerable species on the IUCN Red List. Their main habitat is naturally marshy areas known as fenland, but spider populations have been decreasing mainly due to loss and degradation of their habitat. With the continued re-establishment and protection of wetlands, it is possible to increase their range through releasing captive reared stock.

Invertebrate Keeper Jeff Lambert says: “These iconic species walk on water and use their legs to detect ripples on the surface and catch their prey – in effect the water is their web. It’s a great privilege for ZSL London Zoo to help rear and re-introduce this charismatic species.”

One of the largest spiders in Europe, adult female fen rafts have bodies of about 20mm in length – about the width of a 50 pence piece. But these recently hatched spiderlings start off only a few millimetres long and will grow as they are fed and cared for in their specially adapted ‘spider shed’ quarantine unit at ZSL London Zoo.

Head of invertebrates, Dave Clarke added: “It’s a privilege to work with these rare and beautiful spiders, and have the opportunity to do our part in releasing them back into the wild.”

ZSL London Zoo is one of ten zoos and aquaria to have become foster-parents to nearly 2,500 fen raft spiderlings, which will be reared for two months until they are robust enough to face the outside world. In a project with Natural England, they will be returned to suitable sites within their natural range to establish new colonies. Results of the releases will be monitored for success next year; and previous studies have shown that they have every chance of helping to ensure the survival of this magnificent native species.