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Sand lizard markings |
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Vicar
Senior Member Joined: 02 Sep 2004 Location: United Kingdom Status: Offline Points: 1184 |
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Posted: 12 Sep 2004 at 12:45am |
Do the different Sand lizard colonies have slightly different markings ? I only have a small sample set at the moment, but I can see similarities between the Hankley 'Sandies' markings and a different trend with the Frensham ones. Or am I being hoplessley subjective ?
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Vicar
Senior Member Joined: 02 Sep 2004 Location: United Kingdom Status: Offline Points: 1184 |
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Right, now have a pretty decent selection of pics of Surrey Heath Sandies, and have even knocked up a format for recording the markings to distinguish individuals. What I now need is a system for characterising the markings, which saves me from checking each old photo against a new pic. Obviously location can be a fliter, but I need something which represents the markings, maybe numerically. This MUST have been done with such things as fingerprints before pattern-matching on modern PCs. Before I re-invent the wheel and create my own system, does anybody know of an extant system in use ? would make far more sense for me to adopt a system than create a new one ! Any help out there ?? |
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Vicar
Senior Member Joined: 02 Sep 2004 Location: United Kingdom Status: Offline Points: 1184 |
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Thanks for that David, What I am thinking of is developing a system which cues on characteristics of the marking pattern, not exact representation. (Or adopting one if one exists). One example may be; on the back patternation, where there are elements of black banding which connect unbroken between both dorsal stripes, this could be represented as a boolean 1 or 0. There MAY be a way of codifying some aspects of patternation. I shall rely heavily on the expertise of this forum to suggest possible characteristics. Once we have a set of ideas, I can then just apply to the pictures I have to determine feasibility. If it looks hopeful, I'll liaise with Alan here in Surrey, and then maybe expand to see if such a system works with Dorset specimens. Very interested to hear how the Newt characterisation worked out. Thanks for the interest ! Edited by Vicar |
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Vicar
Senior Member Joined: 02 Sep 2004 Location: United Kingdom Status: Offline Points: 1184 |
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Cheers David, My German is passable, or failing that I'm still in contact with my Austrian Ex. who happens to be a technical translator :P either way I'm sure it would be useful. The email link on my signature should work. I'll keep this thread updated on any progress. |
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Vicar
Senior Member Joined: 02 Sep 2004 Location: United Kingdom Status: Offline Points: 1184 |
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Got a half-decent pic of what I would consider a typical Surrey male sandy, how do the markings compare with Dorset specimens ? |
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Alan Hyde
Senior Member Joined: 17 Apr 2003 Location: United Kingdom Status: Offline Points: 1437 |
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Very Nice pics Steve and David
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Chris G-O
Member Joined: 14 May 2003 Location: United Kingdom Status: Offline Points: 29 |
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Hi Vicar (Steve),
I doubt you'll find any differences in patterns between Surrey & Dorset without a massively intensive study with complicated analysis. The only regional differences i'm aware of are the Merseyside race which have very broad dorsolateral silvery grey bands between the lateral and the dorsal markings. However, in ALL British populations there is just so much variation, i cannot see how you'd find a useful distinction. Out of interest, did you end up getting a licence yourself? We were discussing putting you on the HCT one. You sound like you're out a lot. It's important that your results get onto the national database and are put to good use for the conservation of the species. cheers, Chris |
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Iowarth
Admin Group Joined: 12 Apr 2004 Status: Offline Points: 743 |
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Further to Chris GO's post please see my reply to the (now nearly a year old) topic re races. Although it sets out general principles re the differences between races (and they are pronounced enough so that most of us with experience can identify the race by appearance alone about 70% of the time) I have to agree with Chris re the difficulty in applying a universal rule. It can be no more than guidance. As I said in the post under the topic mentioned:- "Having said this - every variation can be seen in every location. it would appear that the variations occur naturally and a combination of trace minerals in the habitat and natural selection (i.e. which pattern provides the best camouflage) are the determinants as much as the racial genes." |
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Chris Davis, Site Administrator
Co-ordinator, Sand Lizard Captive Breeding Programme (RETIRED) |
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Vicar
Senior Member Joined: 02 Sep 2004 Location: United Kingdom Status: Offline Points: 1184 |
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I was chatting with Emma Hutchings (sp?) from Marwell PT the other day, she mentioned they have somebody looking at the automated recognition of an individual L.a from a scanned pic, they are adapting the method used for Zebras (stripes). Maybe Chris G-O's student knows more?. Assuming they are using a neural-net based system (that's a guess by me), the weightings may give some indication of racial differences. (just a thought). When captive L.as are reintroduced...is stock from the appropriate race used ? |
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Iowarth
Admin Group Joined: 12 Apr 2004 Status: Offline Points: 743 |
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That does sound interesting. Certainly Sand Lizard markings seem to be as individual as fingerprints and effective as an identification at this level. I am not so sure at race level because all variations can be seen in all races at some time. I doubt if it could improve much on the "expert's" identification. Regarding re-introductions of La, yes, where it is clear what race would have been found in a given area then only the appropriate race is used. For example, Welsh re-intros being thus far restricted to the North & West use the Merseyside race as there is historical contiguity of suitable largely dune habitat. Further South there are areas where it is difficult to decide whether Surrey or Dorset animals are more appropriate but these two races are far more similar to each other anyway. |
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Chris Davis, Site Administrator
Co-ordinator, Sand Lizard Captive Breeding Programme (RETIRED) |
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