Surface Temperatures and Themoregulation - July - Almeria

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Surface Temperatures and Themoregulation - July - Almeria

Postby Tortoise Trust » Thu Jul 07, 2011 3:44 pm

This graph tells its own story...

Image

So does this:

Image

Look closely... this is a tortoise in retreat from the heat:

Image

Carapace temperature?

Image

Yes, that is reading right! Obviously, that is not the core (body) temperature...

Some observations:

At this time of year tortoises are active from about 8.15 am to around 10.00 am, then they retreat.

They do not emerge again until around 8.45 pm at night and remain active until the sun goes down (about 10.0 pm) , when they retreat back under vegetation:

Image

Total daily activity is approximately 2.5 to 3 hours. That will reduce as it gets even hotter. This includes grazing, early morning basking, etc.

Actual grazing time is approximately 30 minutes per day.

Exact times of emergence and retreat are governed not only by ambient conditions (temperature, shade intensity and windchill factor, etc.), but very much by body size. Smaller animals have different behaviours at a given temperature than full grown adults. This is a product of body mass, thermal inertia, and the differential between carapace temperature and core temperature. Small animals basically heat up faster.

I have some quite interesting infra-red thermographs that illustrate this rather well.
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Re: Surface Temperatures and Themoregulation - July - Almeri

Postby Matt » Fri Jul 08, 2011 7:10 pm

Interesting to see the Carapace temperature reading of 41 °C +, as I regularly find my girl around that temperature. (weather permitting :roll: )
I have to say that was a little worrying at first given the temperatures you gave me here.

viewtopic.php?f=18&p=53728#p53728

I put her higher carapace temperature down to her size and weight, but it's nice now to see a tort in the wild reaching a similar temperature. 
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Re: Surface Temperatures and Themoregulation - July - Almeri

Postby Tortoise Trust » Fri Jul 08, 2011 7:45 pm

What I said there is correct. Generally, once carapace temperatures rise above 38C they retreat. Peak activity tends to be below 34C. You may find them with slightly higher carapace (not core) temperatures than 38, but I can pretty much guarantee that at this point they will be taking active measures to try to reduce it:

Hiding
Burying in scrapes/burrows

It is pretty much the point at which they start to have a few problems.

A concern in cold climates is that they allow the carapace to overheat (possibly sustaining burns in the process from heat lamps) in an attempt to get the core temperature up.. that is not a problem in the wild normally, as the background ambient, and hence differential is so much closer to that desired.
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Re: Surface Temperatures and Themoregulation - July - Almeri

Postby Matt » Fri Jul 08, 2011 9:44 pm

The temperatures you gave before all sounded fine to me. 

If we do get some nice weather I will normally find her in one of her scrapes, burrows or caves. But as the heat here isn't quite so intense as you have it or in her natural habitat she quite often leaves part of her shell still exposed to the sun. This exposed area I may find to be quite hot (low 40's), which as I said was a worry with what you said about thermal burns.
Unfortunately, even though it is summer I still have to use a heat lamp (14 °C max here today), I have raised it as high as I realistically can and have a fan heater to raise the background ambient temperature if needed. A higher background temperature (as you said) definitely helps reduce basking time.

So from the information you supplied above, am I right in saying you're not likely to find a tort out on a substrate that is getting close to their max body temperature.

It looks like they are all hiding before the ground temperature reaches
40 °C. 
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Re: Surface Temperatures and Themoregulation - July - Almeri

Postby Tortoise Trust » Sat Jul 09, 2011 7:18 am

Matt wrote:So from the information you supplied above, am I right in saying you're not likely to find a tort out on a substrate that is getting close to their max body temperature.

It looks like they are all hiding before the ground temperature reaches
40 °C. 


Pretty much, Matt - yes. Here is some data from one probe (the one used to generate the graph). It contains 6000 measurement points. You can download it here in Excel .XLS format:

ttphotos/julytempspread.xls

Note the emergence and retreat times cited above, and you can see the 'trigger' points quite clearly. These have been confirmed by multiple measurements and observations over many months both this year and last year. It is very consistent. Obviously exact times of day this occurs is seasonal, but the pattern, and the temperatures, are very clear.

This is quite significant data. I don't think it has been done before like this.
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