Natural England ecologist Dr Helen Smith has been carefully hand raising thousands of baby spiders since the spring and they have just been released back into the wild in Suffolk. The fen raft spiders that have been released into Suffolk Wildlife Trust reserve at Castle Marshes is one of the rarest species in the UK. The spiders had to be kept in individual test tubes as they grew to stop them from eating each other.
The 3,000 spiderlings were kept in the kitchen of Dr Helen Smith and had to be hand fed their favorite meal of flies. She said: “Hand rearing over a thousand baby spiders is an exhausting job. At one stage I was up until 2am, seven days a week, feeding flies to hungry young spiders in my kitchen. I’m excited and relieved to see them making their own way in the world – and I can finally have my kitchen back.”
The fen spider is now only found in 2 locations in England and the spiderlings that have now been released into Castle Marshes have been reared from parents of both the sites. By forming the population from two different locations it is hoped that there will be a larger genetic diversity and this will help to increase the chances of success for the re-introduction programme.
The fen raft spider, Dolomedes plantarius, is the largest spider in Europe and was only discovered in the UK in 1956 by arachnologist Eric Duffy. A second UK population was discovered in 1988 and in 2003 a third population was discovered in South Wales. The fen raft spider is one of only two spider species that has the full protection of the law in the UK. The spider has been part of a Species Recovery Programme since 1999.
As well as introducing a new population into the wild extra spiderlings were introduced into the Redgrave and Lophan Fen nature reserve to help support it’s dwindling population.
The fen raft spider lives in ditches of fen habitats. It ‘s body can grow up to 23mm in length and spans 70mm when it’s legs are taken into account. They colour ranges from black to brown and have striking cream or white stripes across their body. They are quite particular about the type of habitat they live in and need neutral or alkaline water bodies. they feed predominately on aquatic invertebrates – dragonfly larvae and pond skater – though they are also known to feed on tadpoles and small fish. Fen raft spiders normally take two years to mature into adults and it is thought that they hibernate over the winter period. It is thought that the fen raft spider hatches during June and July.
One of the greatest dangers to the raft fen spider in the UK is climate change and sea level rises. One of the populations at Pevensey Levels are living on salt marshes reclaimed during the Middle Ages and these could be lost as sea levels rise.
Editors note: Yes I know I’ve put it in the insect category and spiders are not insects but I will soon change the insect category to Arthropods.
photo credit: Dr Helen Smith
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