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RAUK - Archived Forum - Handling neos and collecting data

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Handling neos and collecting data:

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GemmaJF
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Posted: 02 Jun 2008

Hi all,

I would like to monitor the grass snake population in the garden. We have now at least two cohorts of young snakes, and would be really interested to monitor growth rates and also study how long they stay around before dispersal.

I'm looking at individual ID, measuring weight, measuring length - and recording anything that you guys think would be worth keeping a record of.

I'm a little reserved as this will require a fair bit of handling. What do people suggest. Is tubing OK with such tiny animals? I'm quite use to catching the things but all the extra handling over a period of time to get measurements and ID photographs is a little off-putting. Advice please!

Just to add, I'm currently favouring collecting them up in a bucket, cooling them down for a bit in the shade and dropping them in a squish box, any thoughts welcome

GemmaJF39601.2696412037
Gemma Fairchild, Independent Ecological Consultant
Robert V
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Posted: 04 Jun 2008

Gemma,

not sure there would be much value in photos as the collars and scales will warp and change as they grow.

Why not build an enclosure for a while and really get some growth records going? That way, you could track the difference in growth rates between males and females.

Just a thought.

Rob


RobV
Alan Hyde
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Joined: 17 Apr 2003
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Posted: 04 Jun 2008
Hi Gemma, All sounds very interesting.

My only thought is, Could you monitor the time before dispersal after handling? From my experience grassies rarely stay in the same place once caught and handled

Al
O-> O+>
GemmaJF
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Posted: 04 Jun 2008

Rob for ID I was going to photo the first 20 ventral scales, this is becoming a popular technique for Nn as the chequer pattern is unique for each animal - I'm not sure though if this can be applied from neo to adult. Couldn't enclose them I'm afraid though, I couldn't bear it as the wildlife garden is there for all to come and go freely.

Al, good point, not much point trying to study residency if I scare them all away, really what I need is a non-intrusive way to photograph the first 20 ventral scales... more pondering required

I must do something though, I have for the first time in my life a study site that won't get mowed, grazed or bulldozed. It might be tiny but what a sample point, a grass snake nursery just outside the backdoor 


Gemma Fairchild, Independent Ecological Consultant
GemmaJF
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Posted: 05 Jun 2008

so many views of this thread so few comments??

Anyway started the project today with my first slough collected and first capture of a juvenile. Squish box technique worked perfectly, very easy, very little handling involved. Was unlucky that I missed a neo under the same felt, but I'm sure you have all been there with one in the hand and the possible option of losing it if you go for the other.

Once in the bucket with some grass and left for a bit this small snake became very placid as they do after the intitial shock of being caught.

Easily encouraged it to sit in the squish box that needed no more than the foam placing lightly inside to secure the animal for an ID shot. That's all I need for now, I think I can estimate SV from the photo and have enough to recognise the animal. I even got a slough it had left behind under the felt. So day one is looking good

Markers above are 1cm spacing to give an idea of scale.

PS Thanks due to Brett Lewis who first posted regarding squish boxes for snakes. I had never thought of using them for smaller snakes. Have to say it was the least stressful ID I think I've ever done and number 0001 was soon back under the felt where it belongs. Excellent.


Gemma Fairchild, Independent Ecological Consultant
adamanteus
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Joined: 03 Jun 2008
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Posted: 05 Jun 2008
Gemma, you can get pin-sharp focus, top quality ventral shots by placing the snakes (in a glass box if required) on a colour flat-bed scanner, as used with a PC.... plus it loads the pic directly onto the PC.  Very easy to lay down a measuring scale too. adamanteus39604.7000231482
James.
GemmaJF
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Posted: 05 Jun 2008
That sounds like a plan adamanteus, problem with the camera is distortion from the lens and it took two of us, one to hold the squish box and one to get the shot, I managed to correct the image in photoshop but it was a bit fiddly, will give the scanner a try
Gemma Fairchild, Independent Ecological Consultant
adamanteus
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Posted: 05 Jun 2008

Here's an example of the quality and clarity you can achieve with a scanner....

This photo was taken to illustrate necrotic/ulcerative dermatitis in Thamnophis sirtalis.

adamanteus39604.7501851852
James.
GemmaJF
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Posted: 05 Jun 2008

Fantastic image easy to make out every ventral scale, was the dermatitis a result of too damp an environment or is there another cause?

Just done a couple of dry runs with a bic pen in the squish box, looks good, I'll post up an example of a scanned grassy when I get the next one


Gemma Fairchild, Independent Ecological Consultant
adamanteus
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Posted: 05 Jun 2008

[QUOTE=GemmaJF]Fantastic image easy to make out every ventral scale, was the dermatitis a result of too damp an environment or is there another cause?[/QUOTE]

The result of poor captive care, I'm afraid..... Damp and dirty!


James.
Caleb
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Posted: 06 Jun 2008
[QUOTE=adamanteus] Gemma, you can get pin-sharp focus, top quality ventral shots by placing the snakes (in a glass box if required) on a colour flat-bed scanner, as used with a PC....[/QUOTE]

I've used this technique with amphibians- I used a perspex squish box on the scanner. I had real problems keeping them still during the time needed for the scan- only about 1 in 3 scans were usable. The ones that did work were very sharp, as you say.

I've also made a stand for the squish box, with a mirror mounted at 45 degrees to view the underneath- a bit tricky to get decent lighting for this, though.
GemmaJF
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Posted: 06 Jun 2008

The current squish box I have is cut from a piece of plastic packaging with very soft foam. It works well enough for keeping them still (though snakes tend to stop moving even if you just place a finger on their back). First results of the scan, the neo I missed yesterday was easy to collect from the exact same spot in todays murky overcast:

 

I don't think we had full resolution on the scanner, but the result is acceptable though it took a few passes to get the whole underside in good enough focus, bearing in mind we were scanning through the base of the squish box the result is impressive and the whole process easier than using a camera, it is also dimensionally correct which is ideal. Good enough for ID, and I have one shot of the tail that will allow a scale count.

Next I'm going to try an open ended box so I can squish them directly to the plate on the scanner

One last thing, had a hunt around for some software to take measurements directly from the images, quite a bit of commercial stuff, but the best I found is a free one called GRIP. It allows you to draw a free hand curve and return its length after calibrating the image, thus easily measuring SV and tail length - something that photoshop doesn't have. If anyone knows any other software that might be of use I would be interested.


Gemma Fairchild, Independent Ecological Consultant
adamanteus
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Posted: 06 Jun 2008
[QUOTE=GemmaJF]

Next I'm going to try an open ended box so I can squish them directly to the plate on the scanner [/QUOTE]

Yes.  It's best to have the animal directly on the scanner plate.  When I do it, I don't attempt to restrain them or keep them still in any way.  I just wait until they settle then start the scan.


James.
adamanteus
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Posted: 06 Jun 2008

http://www.serpwidgets.com/Apps/apps.html

This link should take to a snake measuring application....(if I posted it right)


James.
GemmaJF
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Posted: 06 Jun 2008
[QUOTE=adamanteus]

http://www.serpwidgets.com/Apps/apps.html

This link should take to a snake measuring application....(if I posted it right)

[/QUOTE]

The link works, just what I needed and much easier than trying to draw a curve with the mouse

The problem I had with neo unrestrained was he would keep his head up all the time, might need to let them cool down a bit more as he was very keen to hide under the scanner

GemmaJF39605.2726967593
Gemma Fairchild, Independent Ecological Consultant
Caleb
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Posted: 06 Jun 2008
The UTHSCSA Image Tool has also been recommended here before for line measurement- seems to work OK.
GemmaJF
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Posted: 06 Jun 2008
Ta Caleb, I'll try that out also
Gemma Fairchild, Independent Ecological Consultant
Robert V
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Posted: 06 Jun 2008

Gemma,

can I ask, when are you hoping to recapture to recheck the ventrals? next month, next year? those patterns will definitely warp as they grow, they cannot possibly remain the same. How will you be sure that they will be the same snake? If they are completely different, it could give a general indication, I grant you, but categorically, nah, I don't reckon. Besides which, don't you think all that partial crushing and flashing lights is a good idea????

R


RobV
Robert V
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Posted: 06 Jun 2008

PS,

Im just waiting for the Japanese to come up with a microchip tracker that sticks to one scale like a tick - now that will be progress.


RobV
GemmaJF
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Posted: 06 Jun 2008

Rob you assumptions contradict at least three papers where individuals were 'tagged' by the first 20 ventrals. Take a look at the two images on this thread. I can't see any difficulty distinguishing these individuals in the future. Futhermore, as previous studies were capture recaptures of adults I should be able to establish if the technique works from neo. Worthy in itself and I have identified adults over several years using the technique. I would anticipate some changing of the pattern, but what off it if it still provides positive ID?

The scan bed isn't a bright light, far less light than a basking snake will be exposed to and certainly far less than a camera flash, so no issue there.

Squish boxes, the argument has been done before, a properly restrained animal is less stressed than one in the hand which needs to be gripped at some point. Partial crushing is a silly term and likely to give completely the wrong impression of what is being done - I assume you do not realise it has been used as a standard technique for GCN ID for years.

Adamanteus has already stated that it is possible to get the scan without it, so I will find the best technique for me and the animals that is least stressful for both parties. As it is the one that was scanned today must have been one of the smallest grass snakes I've ever  handled and it was returned without harm.

PS Rob, if you want to drop by at any time and see what I'm up to first hand you are always welcome, you will see that I'm being very careful and minimising the handling 

GemmaJF39605.5445023148
Gemma Fairchild, Independent Ecological Consultant

- Handling neos and collecting data

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