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Bid to help spread of endangered spider

PUBLISHED: 19:46 18 June 2008 | UPDATED: 10:32 12 July 2010

EFFORTS may be made to try to establish new colonies of a rare, endangered spider.

The fen raft spider, found at Redgrave and Lopham Fen, has only two other known populations: near Swansea and at Pevensey Levels, near Eastbourne.

EFFORTS may be made to try to establish new colonies of a rare, endangered spider.

The fen raft spider, found at Redgrave and Lopham Fen, has only two other known populations: near Swansea and at Pevensey Levels, near Eastbourne.

At the fen, the spider, one of the biggest and arguably the most beautiful of the European species, occupies a relatively small area.

And, despite extending its territory by a 75-metre “spur” recently, it shows no sign of colonising potentially suitable areas nearby.

The population there remains vulnerable, as they do at the other two sites, which are also more prone to suffer as a result of sea level rise and possible saltwater incursion.

Now, Helen Smith, a spider expert who monitors Redgrave and Lopham Fen for Natural England's species recovery programme, is exploring the possibility of human intervention to try to establish further colonies, not only there but further along the River Waveney and maybe even elsewhere in the UK. If the proposal does proceed it will only be with the permission and support of Natural England, which would have to be satisfied there was a good chance of success.

Saving the fen raft spider was one of the targets, along with preserving internationally-important plantlife, in a £3.2 million restoration project completed at Redgrave and Lopham in 1998 to reverse a drying-out process that had progressed for decades. The project has served to sustain the creature's local population, which would have otherwise been at severe risk of extinction because of falling water levels.

However, the spiders have failed to colonise areas of the fen deemed suitable after restoration, and this has led Dr Smith and other experts to consider intervening. She explained: “There is no doubt that the fen raft spider is in a very insecure position, and help may be needed.

“We are doing a scoping study, looking more widely across the fen to identify prime sites. We have more knowledge now because we have the results of PhD research into the genetics of the raft spiders and the conditions that sustain the creatures.”

Dr Smith said the reason for the population's failure to respond to habitat improvements at Redgrave and Lopham was still not fully understood. “It could be that the water quality is just not good enough. We haven't found any evidence of genetic problems from which they are unable to recover, although we have found that the spiders are poor dispersers and so are very slow to colonise new areas of suitable habitat.

“We have also found that poor breeding success can occur not only in drought years but the following year because the adults are relatively small.” she said.

The number of egg-laying females is still being counted in tens instead of the thousands that had been expected by

now.

Each female can have two breeding cycles annually, and each

can carry up to 600 eggs.

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