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I have used some signatrol data loggers in T.hermanni habitat in Spain and also where I live (about 70km) for comparison. I have read the data of last two months and I am a little confused.
All around the province of Catalonia there are government weather stations. They measure the temperatures, solar radiation, wind, rain…The data are in internet and they are supposed to be very reliable (they use professional equipment and the data are checked before posting in internet ) http://www.meteo.cat/mediamb_xemec/serv ... dades.html
The signatrol data loggers are calibrated and are also supposed to be very reliable
http://www.signatrol.com/Datasheets/SL54TH.pdf

Regarding the data logger where I live:
There is one of those weather stations less than 1 km from the place where I put the data logger. I put it protected from the rain and in the shade, but with good air circulation.
When I look at the minimum temperatures there is often a difference of 6ºC between the data logger and the weather station (always higher in the data logger).
Between the maximum temperatures the difference is only 1-3ºC , sometimes higher the signatrol, sometimes the other.

Regarding the data logger in tortoise habitat:
The distance between the data logger and the weather station is about 10 km. I protected it from rain with rocks and some shade of a tree, but letting the air circulate.
As an example, the 26th of June, the data logger tells a maximum temp. of 41ºC and a minimum of 21ºC. The weather station tells 31,1ºC and 15,1. It´s a difference of 10ºC and 6ºC! The standard shade temperatures (the ones on TV) only reach the 40ºC for a few days in July or August!
With the other days more or less the same.

To check the two data loggers, I used them in my house, put together, in different conditions (inside the fridge, on a warm room…) and I also measured the temperature in those places with a mercury thermometer. The graph between the two data loggers was nearly identical, with a slight difference of 0,5 and 1ºC in temperature measurements in cold places. Between humidity the maximum difference was of 10% (85-95%).
They were similar to the thermometer temperatures.

So, what is happening? Can microclimates explain this?

The data logger in hermanni habitat. The rock is in an angle and forms a roof for the data logger but lets good air circulation.



Jordi

Jordi,

Yes.

They normally take the weather station temperatures in free air, at least 1m above ground level. You are seeing the effect of the ground, and of the surrounding rocks, not just measuring the temperature in free air. You will often record ground temperatures of 50C when the weather stations and the free air temperature is only 35 C.

Using white rocks can help, as they absorb less solar radiation... you may also get higher humidity readings due to the partly enclosed space caused by the rocks.

Of course, this also shows just why weather station readings can be very misleading when looked at by tortoise keepers! The readings you have taken are much more accurate when considered from the point of view of a tortoise. Your readings are closer to what they really experience than those of the weather station.

Another point is that altitude will have a big effect, and that two temperatures taken 1km apart will always be different. At 10km they will be very different.

Thank you, I was beginning to think that the data logger didn´t work properly . It´s an amazing difference. It is really very interesting.
These are the data of the last months in a high tortoise density area (Testudo hermanni hermanni). This spring has been unusually rainy.





Jordi

It is easy to see the days when it rained!

Yes. Today I have been in the data logger place. Later I will post pictures of a very quicky drying vegetation. It was 35.5ºC on the shade (around 12:00), more than 44ºC under the sun. I didn´t find any tortoise. I wonder why
Jordi

Last week it was quite hot in T.hermanni habitat. You could feel the warm air draughts. The cicadas were singing. Cicadas and summer heat always go together here. The vegetation looks like dead, although it is not. All is turning to a yellow-brown colour. I can just admire how well adapted the vegetation is to that climate. Some of the most common plants in the habitat, the Rock rose (Cistus albidus) the Montpelier Rock rose (Cistus monspeliensis) and the Spiny broom (Calicotome spinosa) are now loosing the leaves and look as though a fire has passed over them. They are full of seeds these days. Local people have told me that they will look worse in a few weeks, but when the rain and cooler temperatures come back, they will resurrect and green leaves will appear again.





The lavender also looks like dead. I posted pictures of this field before, this is from an area particularly rich in tortoises. In this field they found several predated nests last summer.







If you just turn, this is what it looks like, there is a small stream down there.



Imagine hectares of dry vegetation, with very high temperatures, and add the human influence (electric lines, car and other machine engines, empty glass bottles, careless smokers, barbecues…). Most summers, as soon as we have some heat wave and reach the 40ºC, specially if there is wind, forest fires appear somewhere in the country.
This tree is Cork Oak (Quercus suber), very common in T.hermanni habitat. It is also adapted to the dry summers, it has small and hard leaves and looses many of them in the dry months. The cork bark is fire resistant and is an adaptation to the summer fires. All those trees had fire signs, but all were alive.




Jordi

Nice photos, Jordi. They really show how different the T. h. hermanni habitat is from our T. graeca habitats.