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Conservation of the fen raft spider

Updated Friday 7th October 2011

The Saving Species team talks to Helen Smith about the understanding and conservation of the fen raft spider

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Interviewer
Well, what a glorious autumn day here in the County of Suffolk.  I'm actually on the open marshland at the Suffolk Wildlife Trust nature reserve of Carlton Marshes.  And I'm actually here for a spider, and the person that’s going to introduce me to these spiders is Helen Smith.  Helen, what is it you're actually doing?

Helen Smith
Well today we are putting out some tiny fen raft spiders on the ditches on this reserve to start to set up a new population.  This is one of Britain’s rarest, biggest and most beautiful spiders.  It occurs in only three places in the wild in the UK, and we’re just starting work on Natural England’s programme of introducing it to new sites to try and secure its population in this country for the future.

Interviewer
So did this area, Helen, did it ever have fen raft spiders in big numbers?

Helen Smith
Well we don’t know the answer to that, we’re never going to know the answer to that; they weren’t discovered in the UK until 1956.  I think we just have to make some sensible assumptions based on the current distribution, which is here in Suffolk, down in Sussex and across in Wales, and a species that relies on clean, lowland wetlands, and we know what’s happened to the majority of our clean lowland wetlands, so I think it’s almost inevitable that we've lost this species from large areas of Britain.

Interviewer
Why choose this particular site and not any other site around?  What’s particularly good about this site for them?

Helen Smith
Yeah this site is part of the Suffolk Trust’s move to try and connect back together a lot of its wetland nature reserves along the lower Waveney, creating huge areas for wildlife, and so introducing spiders here, and we’re also introducing them to another site a bit upstream, is a first step, stepping stones if you like to start to create a much bigger joined up population and utilise that big network that the Trust are creating.  But we've been working towards the translocation programme really for the last five years, very much starting to look at what sites would be suitable and actually how to achieve it in practice.

Interviewer
Have you actually released before, or is this the first of the releases?

Helen Smith
No, we started last year, we released at a site just upstream from here, and just in the last few months we've been starting to see the spiderlings looking fabulous out there on the water soldier over there, you know, stripes gleaming in the sun.

Interviewer
So a real success.

Helen Smith
Yeah, very, every time I see one there.

Interviewer
A real success, especially after the winter we had.

Helen Smith
Yeah, no, it just so exciting every time we see one, particularly when we find a new ditch with one on, they look so at home.

Interviewer
Well, Helen, you’ve just got out of the tub a full adult live raft spider.  What a beautiful specimen.

Helen Smith
Yeah, she’s fabulous.

Interviewer
She’s very dominantly, kind of like a muddy brown, isn’t she?  Sort of like an estuary brown.

Helen Smith
Yes.

Interviewer
With these two very distinctive bands going around either side of the abdomen?

Helen Smith
And the thorax.

Interviewer
And the thorax.

Helen Smith
Yeah, sort of like go faster stripes really, but they're sort of a goldie coloured now, but often in the younger spiders they're brilliant white on a black background.

Interviewer
And what’s the difference between the male and the female?

Helen Smith
Well nothing really until their sort of penultimate moult when they become sub-adult, and then suddenly the male starts to acquire clubbed ends to his palps, which become the insemination organ in the adult.

Interviewer
Is it true they go under the water as well?

Helen Smith
Yeah, absolutely, yeah they spend quite a bit of time underwater.  So sometimes it’s an escape response from predators.  So while I'm monitoring them on Redgrave and Lopham Fen I get in the water and work with them there, and some spiders will go straight underwater as soon as I get in.  But you can often see them there because the hairs on their body trap air and so they look glistening silver underwater.  But they also hunt underwater, so they’ll catch sticklebacks and water boatmen underwater.

Interviewer
So this is the adult, now what about the young ones?

Helen Smith
The young ones look exactly the same, just brighter, miniature.

Interviewer
Okay, now we can hear you rattling around there, and what you're actually carrying what looks like a, well, it’s a plastic tray, and inside that plastic tray are, it looks like hundreds of test tubes.

Helen Smith
Well, it is hundreds of test tubes.  We've got about 600 tiny spiders to put out here today.  These are basically the babies of spiders taken from Redgrave and Lopham Fen in June with egg sacks.  So they hatch their egg sacks.  We potted up the spiderlings into individual tubes to stop them cannibalising each other, and they’ve been fed in those tubes, and we can get very, very high survival rates that way.  So we've bred something like two and half thousand baby spiders this year.  So that’s me working with, lovely collaboration with several UK zoos, and the other really big contributors are volunteers, who make a huge difference to this project and has really carried me through some dark days with this project.

Interviewer
So how do you actually rear a spiderling?

Helen Smith
Well it’s sort of, it’s quite easy really.  I mean once they're about a week old, which is the stage where they'd normally leave their nursery, they go into the test tube with damp cotton wool in the bottom, and we have to get fruit flies in there for them on a very regular basis.

Interviewer
So they really do spend their early life in these tubes.

Helen Smith
Yeah, they do.

Interviewer
They're not just being transported today.

Helen Smith
Yes.

Interviewer
So Helen’s got a group of test tubes in her hand now and she’s checking them over.  Very thoroughly I must add, Helen, why are you checking them that thoroughly?

Helen Smith
Well I want to be quite sure that nobody’s in the process of changing their skin, because they usually attach themselves to the lid, and just before, during and just after skin changing they're very vulnerable because they're so soft and things can go wrong if you disturb them at that stage.  But this lot look fine.  And you can just see the little shed skins in there, from last time they did it.  You can actually see the white stripes on the shed skins.

Interviewer
Yeah.

Helen Smith
So the tubes are strung together with lines of masking tape, and I do it that way so that they're well-spaced out as they leave the tubes, rather than ending up in a heap where…

Interviewer
So Helen’s undoing the top of the test tubes.  I'm looking inside one of those tubes at the moment, and they really are tiny spiders.  You can actually see the brown back on one of those, almost like a rusty brown back.  One’s come out, lowering itself down on a thread into the vegetation, and it’s off into its new world.

Helen Smith
It’s quite nerve wracking, the whole process, I find, you know, introducing something to a site where it probably hasn’t been for a very long time.  And however carefully you follow the guidelines for translocation, and we certainly do, there’s always that bit of unknown out there, we can never be quite sure.

Interviewer
But that’s good, isn’t it, you care.  You don’t just care; I can really hear you're passionate about these spiders.

Helen Smith
Well they’ve lived with me for a long time, so you get to like that about them.  I am passionate about seeing their population restored in the wild.

Interviewer
So these spiderlings now, we can see that they're making their way out quite slowly and then lowering themselves from the tubes down into the vegetation by their threads.  How do they actually live on the water, how do they do it?

Helen Smith
At this stage they actually spend very little time on the water, but by the spring they will be out sitting along the water’s edge, and they're usually seen sitting where stems emerge from the water, often with their back legs on vegetation and their front legs on the meniscus.  And they have specialised hairs in their legs and their feet and they can detect tiny vibrations in the water surface which tell them where their prey are and where their predators are.  So they're very tuned in with this sort of vibratory sensory system to living on water.  And they use that system for courtship as well, so the courtship is very much based around creating vibrations in the water surface.

Interviewer
Now why do you release at this time of the year?

Helen Smith
Well, two reasons really, I think, you can see there’s very tiny animals, lots of things will predate them at this stage, although as adults they become very fierce predators themselves, but at this stage they're very vulnerable.  And we know from the size of our wild populations, we can get over 90% survival rearing in this way.  So we’re skipping an enormous amount of the mortality that would happen in the wild.

Interviewer
So they're being released now, what happens next?

Helen Smith
Well the ones that don’t get eaten will hibernate during the winter, and I have to say we know remarkably little about what they do in the winter, it’s like looking for needles in haystacks.  They're almost certainly in airspaces in hollow plant stems, some of them could be in airspaces underwater.  If you look at the Pevensey marshes in early spring before the water soldiers come up, you see very few fen raft spiders, and a month later they're absolutely everywhere.  So these ones which hatched this summer will spend next summer growing, they’ll become sub-adult, their penultimate skin change, next autumn, and then the following spring they’ll mature into adults and breed during that summer and die at the end of it.

Interviewer
So we’re not just talking about the release of these, there’s some quite intricate monitoring going on as well, isn’t there?

Helen Smith
Yes, very much so.  So we’re monitoring both the population of the new spiders, and something very much that volunteers are helping with increasingly, which is very valuable, and we’re also doing genetic monitoring of the new population.  So we’re looking at what’s going out and genetically what of that we retain over time.

Interviewer
Presumably when you're doing that work as well, you're finding out that you haven’t got a subspecies.

Helen Smith
Yes, yes, no evidence at all of any barriers to breeding.  We looked at breeding, and we looked at mating behaviour, courtship behaviour.  We looked at survival of the young, we looked at the number of offspring produced, and we’re actually next year we’re going to look at the F2, the next generation as well, just to be doubly sure.

Interviewer
Is there a problem releasing another predator, another spider predator within an environment like this?

Helen Smith
It’s very difficult to give you a very definitive answer to that, but I think the best answer is that the places where these spiders occur in the wild now are three of our richest wetlands, very, very high diversity, and these spiders clearly fit into that ecosystem.  They have a place there; they would have been there in the past.

Interviewer
This area here looks very similar to the area I come from, which is the Somerset Levels.  What’s the chances, Helen, of me having a few spiderlings to take back?

Helen Smith
One thing that we’re going to be doing in the next few years is looking for additional sites for reintroductions.  The action plan for this species suggests 12 sites in the UK by 2020.  We’re currently looking at six sites now.  We’re certainly going to start to look at some of the inland fens, because of concerns that these broadland sites are going to be gradually salinized as sea levels rise.

Interviewer
How long will the monitoring go on for?

Helen Smith
I think monitoring needs to go on almost indefinitely for species as rare as this.  These are animals which are so rare they should be being monitored on a very regular basis.  The action plan for the species has a 2020 target.  If we’re going to achieve that target I think the programme will have to go on probably until 2020, but the monitoring very much longer.  And the habitat here has been through bad patches in the post war years.  A lot of these fields have agriculturally improved, the ditches became eutrophic, and now as you can see they’ve been beautifully restored by the Trust, and so to have one of the species that had been lost back here I think is just very appropriate.

Interviewer
So we’re not only talking about, earlier we were talking about joined up habitats, the fact that there’s more habitats going to be created that are like this, we’re also talking about joined up spiders.

Helen Smith
Yes, joined up spiders, and I think that it adds enormous point to the translocation.  I think if we were introducing to a few more tiny isolated sites, I would see that as having much less future and being much less worthwhile than being able to bring them somewhere like this, where we know that if they do well they can move out through these ditch networks over a huge area of the Norfolk Broads eventually.

12’00”

Fen Raft Spider Copyrighted image Icon Copyright: Chris Sperring/BBC Fen raft spider
 

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