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Pool Frog programme coming up |
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sussexecology 
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Joined: 30 Sep 2010 Location: United Kingdom Status: Offline Points: 411 |
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 Posted: 13 Aug 2012 at 4:39pm |
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Just an idea Caleb - could this be competition with frog and toad populations (niches etc) if they can't compete with those species Or is it because being late breeders that the ponds they use have dried out by the time they come round to breeding? I'm assuming that they return to the same pond each year, as toads do?? If there aren't a cluster of ponds together and so the ponds are isolated, I'm guessing this could make sense. Just an idea though. Regards SE Reptile Ecologist |
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Caleb
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Posted: 13 Aug 2012 at 10:21am |
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As I understand it natterjacks aren't really that specialised (hence their appearance in odd places like the Cumbrian ironworks) but they do very poorly in competition with common frog and common toad. Their main requirement is a pond for late spring/summer breeding that the common species haven't got to first. As pool frogs are also late breeders, maybe they have similar issues? The last site supposedly had low numbers of common frogs. Romney Marsh also has few common frogs or toads- maybe this is part of the reason for the marsh frog's success there? Edited by Caleb - 13 Aug 2012 at 10:21am |
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GemmaJF
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Posted: 10 Aug 2012 at 6:35pm |
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Well I guess my answer to the last part is I've yet to be really convinced by the evidence that they were ever there (as in a widespread historically native distribution as opposed to a one two or a few isolated locations).
I too thought about the Natterjack decline, but I had always considered them to be more specialised in their habitat requirements than Pool Frogs. Kind of more akin to Sand Lizards so to me it is easy enough to understand Natterjack decline in Norflolk and elsewhere, but not so easy to get a grasp on why Pool Frogs would have undergone huge declines particularly in the Pingo area where we can only guess some of the ponds have been filled with water since the last ice age. Are Pool frogs in Europe generally not that fussy about the water bodies they use? Certainly it was the impression I had. I guess it is possible if the notion of the Northern Clade colonising is correct (see you are slowly getting me to at least consider they might have been native) that isolation could have led to some evolutionary changes that led them to favour specific habitats. It seems true of Sand Lizards, Smooth Snakes, Natterjacks and even to some extent Adder that they appear more specific in the UK regarding habitat requirements than they do in mainland Europe, perhaps simply temperature/season related but it is a trend that tends to be noted as animals reach the limits of their range. Taking that in to consideration it would seem more possible that subtle factors led to a mass extinction.
Edited by GemmaJF - 10 Aug 2012 at 6:42pm |
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Caleb
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Posted: 10 Aug 2012 at 12:18pm |
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That kind of depends what you mean by 'site'. There are a number of references to water frogs from various places in the pingo area (and slightly further east), as well as a fen area in Cambs. These and other references from the literature relating to East Anglia were summarised in an EN publication: http://publications.naturalengland.org.uk/file/141025
I think a harder question is why pool frogs disappeared from all the pingos apart from the last site. The reintroduction programme claims that the cause of the final extinction is well understood, but that doesn't really tell us why their range contracted so much during the 20th century. There are lots of good ponds in the area- are they just not quite good enough? Was there a run of poor summers? |
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GemmaJF
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Posted: 09 Aug 2012 at 2:19pm |
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So if they colonised the entire Pingo area historically, which we presume was at the time exactly representative of the habitat that would have existed on the 'land bridge' and therefore ideal for dispersal, why not a widespread distribution in the area to this day?
Other native amphibians are still widespread if increasingly becoming discrete isolated meta-populations to this day, but not Pool Frogs? You see what I am saying, if they were native there should have simply been more of them as historically there would have been no barriers to their dispersal throughout what is now known as the Pingo area of Norfolk. I think also they would have been far more common in the literature of the past. There are only isolated mentions of what are thought to be references to Pool Frogs always linked with very localised locations. I might be wrong, but is it not correct that the Norfolk Pool frogs were recorded only from two sites in East Anglia. One being lost in the 19th Century the other being of course the famous 'last site'. It just doesn't conjure up the picture of immediately post glacial Britain to me, much of Norfolk littered with Pingos and Pool Frogs hopping across a land bridge in a noisy rabble to take up home all over Norfolk.
Edited by GemmaJF - 09 Aug 2012 at 3:00pm |
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Caleb
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Posted: 09 Aug 2012 at 1:40pm |
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They did colonise the pingo area, as the last known site was a pingo site- and this is where the water table dropped in the 80s and 90s. There are also historical records from other sites nearby. There was a (slightly) different colonisation route suggested by: Zeisset I., & Beebee T.J.C., (2001). Determination of biogeographical range: an application of molecular phylogeography to the European pool frog Rana lessonae. Proceedings of the Royal Society, London B, 268: 933-938 (diagram below). I don't remember David Bird's 'mountain' post, but this route doesn't seem to have any mountains in the way.  |
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GemmaJF
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Posted: 09 Aug 2012 at 1:04pm |
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I addressed my doubts regarding the potential colonisation which does not question the existence of the land bridge but rather the ability of Pool Frogs to have used it in my reply to Chris. The Pingo area of Norfolk seems to me to be a whole can of worms in itself. Would the intention be to transport the frogs around to each remaining isolated area from the initial site? It isn't much like Romney Marsh to me. Many of the Pingo ponds are heavily neglected, isolated, silted up or just depressions in the ground and in all there is very poor connectivity in terms of suitable habitat throughout the entire region. I am not saying that transporting the spawn or tadpoles is necessarily a bad thing as obviously disease monitoring is within the capability of those involved. I just wondered if this was part of the plans as fully natural colinisation of the area seems pretty unlikely to me. Of course I then also have the reservation whether or not the Pingo area is actually representative of their 'natural' historic range? Wouldn't some native Pool Frogs still be surviving along with the GCN etc if that was the case? It actually sparks off another doubt too. Lets say there were native pool frogs all over the Fens before they were drained. Why didn't they colonise the Pingo area as well? We can't blame the draining of the fens or the water table for 'extinction' there. Some of the ponds still exist and one would expect a distribution of pool frogs along the lines of the current GCN distribution of modern times of isolated but stable meta-populations. It kind of makes me think the Pool Frogs were always in tiny little populations, almost as if someone put them there in the past..  (Which if it is true also sets of the alarm bell of 'why was this theoretical historic introduction not as successful as Marsh Frog introductions in Kent???)I suppose in all I've talked myself into admiration for the task the team involved took on. It is really something to work back from a handful of records and decide 'was this a representation of a native species' or just the remnants of an 'isolated historic introduction'.
Edited by GemmaJF - 09 Aug 2012 at 1:42pm |
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GemmaJF
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Posted: 09 Aug 2012 at 12:35pm |
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Hi Chris, I must have been given duff information, as I have been told in the past that the early Sand Lizard breeding included animals of unknown origin. That no 'stud book' was kept and that it is more than possible that some of the animals originate from the pet trade. I certainly remember sand lizards being common in pet shops back in the 70's and these were European imports on the whole. But really it is an academic point because as I have stated above in my own mind genetic purity really doesn't matter much on the balance of things. Regarding the colonisation, I can't find it now on the archived forum but David Bird put up an excellent post regarding his doubts of the Northern Clade colonising the UK. I accept the land bridge existed. Unfortunately to use it the Northern Clade would have also had to negotiate a Mountain range. The issue in my mind that has never been fully addressed. Having looked into it for myself it would appear to be a feat of such proportion that they may as well have swum across the North Sea.  Though there is much talk of how the animals 'might' have colonised the UK (with some points that make me doubt it) it seems to me just as likely to this day that they resulted from human introduction. Even if the evidence goes back over 1000 years because people were already by then crossing the North Sea, who knows if they had a few Pool Frogs with them for whatever reason, perhaps Viking kids kept them as pets! Really I would be much happier about the whole thing if the UK Marsh Frogs and other low impact naturalised herp species in the UK had their death penalties removed. You know how I get about NE and glaring double standards. Edited by GemmaJF - 09 Aug 2012 at 12:47pm |
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Caleb
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Posted: 09 Aug 2012 at 9:30am |
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OK, ignoring the Fens. There's the rest of the Pingo area of Norfolk for them to colonise- roughly the same size as Romney marsh, and with hundreds of ponds. The natural colonisation was addressed in: Snell, C., Tetteh, J., & Evans, I. H., 2005. Phylogeography of the Pool frog (Rana lessonae Camerano) in Europe: evidence for native status in Great Britain and for an unusual postglacial colonization route. Biological Journal of the Linnean Society, 85(1), 41-51. As Chris said, they suggested migration via the north sea land bridge, and pointed out that there are other species in Norfolk that are most closely related to Scandinavian specimens of the same species. I've attached the diagram of the suggested migration route below.  |
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Iowarth
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Posted: 09 Aug 2012 at 5:32am |
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Hi Gemma Addressing your point re Sand Lizards, according to our records every re-introduction has been from animals either taken directly from wild UK populations or bred from such animals. Obviously, this does not guarantee they are British animals (a male was found in Northants a few years ago - where did that come from?) but it is, to say the least, highly probably. I also note later that you say "the Northern Clade could not have actually colonised the UK naturally". Can I ask what you base that statement on, considering that a) they are known from post-glacial but pre-introduction fossils and that the North Sea landbridge would have given them comfortable access (remembering that it was somewhat similar to the fenlands). Or am I misunderstanding/taking out of context your statement? I do agree that Grass Snakes should not be controlled but currently their effects are simply being observed and no such proposals have been made. And I also agree that the movement of species by man is as natural an event as any other - also, that condemning captured naturalised animals which have no negative impact on natives to death or captivity because they are not native is ridiculous. I might change my mind on this score should NE decide that all pheasants should be extirpated! Chris |
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Chris Davis, Site Administrator
Co-ordinator, Sand Lizard Captive Breeding Programme (RETIRED) |
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GemmaJF wrote: