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Wild Tortoises and Winter Temperatures

Updated: Mar 26




For many years now, a continuous period of 14 years, we have carefully collected temperature data from literally right next to hibernating/brumating tortoises using precision automatic data logging devices. We discuss some of these, and how they can be used, in a separate article.


Here, though, is some actual data that we want to share with you. This has been an unusual winter in here spain, the warmest on recent record and also, sadly, the driest. This is really bad for tortoises, and for wildlife in general that rely heavily upon the fresh new spring wild flowers for their very survival. We will cover this in a new report to follow soon.


Meanwhile, here are approximately 24,000 separate temperature measurements taken from December 2023 until February 18 2024. Recording frequency was once ever 5 minutes, day and night.


Here is a graph of temperatures right next to a buried Testudo graeca graeca. The tortoise was buried at a maximum depth of 10cm (approximately 4 inches). The tortoises here are relatively small, and in other locations, for example the Balkans or Turkey, the tortoises are both larger, the winter temperatures can be FAR lower, and consequently they dig down to far greater depths. So - this data relates only to Testudo graeca graeca in Spain, and to similar climatic zones in Southern Morocco.




You will note the HUGE differences between daytime and overnight temperatures.


Here is a brief summary.



This reveals a MAXIMUM temperature of 24.2 Celsius (75.56F) and a MINIMUM temperature of 4.6 Celsius (40.28F) over 84 continuous days of recording.


Now, let's look at the above-ground AMBIENT (AIR) temperatures recorded simultaneously.



Here's a summary.



The main takeaway info here is that soil is a fantastic insulator. Although overnight air temperatures fell to -3.0 Celsius (26.6F) temperatures next to the tortoise never fell below 4.6 Celsius (40.28F).

Another feature that is exactly the same as that observed in previous seasons of monitoring is that there are very large differences between night and day temperatures, it is certainly not one single stable temperature.


Tortoises DO and WILL emerge temporarily sometimes...they emerged first around the 25th of January for example, but then it got cold again, before finally emerging fully over the final week.


This year, the lack of rain is likely to have as large an impact as temperatures upon activity cycles.


WE ARE UPLOADING THE 'RAW' DATA FILES FROM A PAIR OF EXAMPLE LOGGERS TO THE TORTOISE TRUST FACEBOOK GROUP PAGE 'FILES' AREA SO IF YOU WOULD LIKE TO ACCESS THESE IN BOTH PDF AND EXCEL FORMAT, YOU CAN DO SO THERE.



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