Jacksons ratio, original paper/article

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Jacksons ratio, original paper/article

Postby Anableps » Wed Jan 10, 2018 8:14 pm

Sorry if I've missed it but is there a link to the original paper or article on this please?
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Re: Jacksons ratio, original paper/article

Postby gettingwarmer » Thu Jan 11, 2018 1:22 am

I'm not sure if this is what you're looking for, but it might be helpful:

http://www.tortoisetrust.org/articles/measuring.htm

Best,
Stephanie
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Re: Jacksons ratio, original paper/article

Postby Anableps » Fri Jan 12, 2018 7:14 am

Thanks Stephanie,
I have read this and did find it very helpful indeed. I am also hoping to find anything written by Dr. Jackson where he describes himself how he devised it etc.
Partly as nerdy curiosity rather than anything else!

Thanks again
Sebastian
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Re: Jacksons ratio, original paper/article

Postby tortydat » Fri Jan 12, 2018 2:56 pm

Anableps wrote:Thanks Stephanie,
I have read this and did find it very helpful indeed. I am also hoping to find anything written by Dr. Jackson where he describes himself how he devised it etc.
Partly as nerdy curiosity rather than anything else!

Thanks again
Sebastian


Goodness Sebastian you are looking to go back a long way as the ratio was compiled I think in the 1960's as there were so few vets with an interest in tortoises at the time. Oliphant unfortunately died in the early 1990's but he was Chairman of the British Chelonia Group for a time so you may well find more information on their site. The ratio was based on wild caught tortoises which are a slightly different shape to many of today's captive bred examples so should only be used as a rough guide and certainly not for very young tortoises.
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Re: Jacksons ratio, original paper/article

Postby Anableps » Fri Jan 12, 2018 8:15 pm

Thanks @tortydat,
I will search on the BCG site and post back if i find anything.
Regarding the body shape differences in wild and captive specimens I totally understand, but where you say it shouldn't be used for really young animals have you an age (or size) that you think it shouldn't apply too and if so why do you think this age/size please?

Obviously the ratio is just a guideline to help people but i would like to see if theres any reference to increments of a centimetre (i.e. the difference between 10 and 10.3. or 10 and 10.8 cm) as when measuring these differences can make a difference, or do we just round up or down or play by ear?
And if so does Dr. Jackson say its that fluid?

Any thoughts on this greatly appreciated and any references to back those thoughts appreciated too.
sebastian
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Re: Jacksons ratio, original paper/article

Postby Stuart » Sat Jan 13, 2018 2:38 pm

You'll presumably be aware of the calculator available on the Tortoise Protection Group website here: http://www.tortoise-protection-group.or ... te/169.asp

It's a bit easier to use than interpreting the graph (derived from the maths)

The original research papers would be interesting to read.
Stuart
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Re: Jacksons ratio, original paper/article

Postby Stuart » Sat Jan 13, 2018 2:44 pm

Anableps wrote: or do we just round up or down or play by ear?
sebastian


If you really want to "play by ear" try Andy's rule of thumb: Pick up the tortoise. If it feels like a "well-filled pie" then it's OK. :D

Over the years, I've found that to be fairly accurate i.e. the JR usually confirms the "pie" assessment!

(There could be a jokey comment in here about pie charts, I suppose, but I'll not make it ;) )
Stuart
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Re: Jacksons ratio, original paper/article

Postby tortydat » Sat Jan 13, 2018 3:54 pm

I'll be perfectly honest and say that I have never really used the Jackson ratio but like Stuart has said used my own observations and kept weight charts for all my tortoises over the years. The pie assessment is a very good guide.

I'm not sure how many tortoises Oliphant had to work with originally as most people wouldn't have bothered to take their tortoises to the vet as they were regarded as disposable pets in the 50's and 60's if they died in the first year you just went back to the pet shop and bought another one. Regarding small tortoises as the graph was based on measurements of wild caught individuals that would have been larger specimens I think it would have been speculative. People weren't breeding them either. All very different to today.
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Re: Jacksons ratio, original paper/article

Postby Sandy » Sat Jan 13, 2018 4:24 pm

tortydat wrote:I'll be perfectly honest and say that I have never really used the Jackson ratio but like Stuart has said used my own observations and kept weight charts for all my tortoises over the years. The pie assessment is a very good guide.

I'm not sure how many tortoises Oliphant had to work with originally as most people wouldn't have bothered to take their tortoises to the vet as they were regarded as disposable pets in the 50's and 60's if they died in the first year you just went back to the pet shop and bought another one. Regarding small tortoises as the graph was based on measurements of wild caught individuals that would have been larger specimens I think it would have been speculative. People weren't breeding them either. All very different to today.



I dont use the JR either, as I watch and observe my tortoises through out the year, if all normal then I hibernate them.
I also used to keep charts etc like Mary:0)
The JR is only a rough guide and not set in stone:0)
Sandy
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