Mediterranean Tortoise Microclimates and Basking Behaviour in Spring
- tortoisetrust
- May 9
- 7 min read
A. C. Highfield
There has long been much debate (and argument) over exactly what conditions wild tortoises experience throughout the year. All kind of 'facts' and numbers are thrown around and cited with great confidence, yet there is rarely a shred of evidence to support any of these claims.
For the past 15 years we have recorded high-precision surface and subsoil measurements throughout the winter brumation period and have produced several reports on this, all with accompanying data, for example 'Wild Tortoises and Winter Temperatures'.
We have also shown that the common belief that arid-habitat tortoises somehow have access to 'humid microclimates' on a continual basis are nothing more than a much-repeated myth. We explored this too in a separate detailed report in our Tortoise Myth Busters series.
One thing that we had been aiming to do for the past three years however, was to gather much more data on the precise conditions that tortoises experience in Spring, during their peak activity periods when the natural vegetation is also in peak flowering season. Unfortunately, the weather did not cooperate and we had continual droughts, barely any rain, and very little vegetation so the conditions were not truly representative. This year (2025) that changed and we had the wettest March and April recorded for a very long time, so we were finally able to get readings of what wild tortoises (Testudo graeca graeca in this case) experience during a 'good' Spring. We have a video you can see on our YouTube channel that show just how wet (and cold) it really was in early March!
This is important, because given the weather conditions during the recording period, we can safely assume that this is almost certainly about as 'damp' or 'humid' as this environment can ever offer. Most years would be quite a lot drier than this. To see just how wet it really was in March this year, take a look at our earlier video on how wild tortoises behave in rain.
We were also fortunate that during one particular measurement cycle we experienced a wide range of weather conditions, including:
Overnight thunderstorms with heavy rain
Daytime downpours
Clear, hot and sunny days with little wind
Overcast days with high winds
Overcast days with very little wind
Therefore, we were able to capture comprehensive 'snapshots' of the temperatures and relative humidity conditions right next to tortoises throughout each of these weather events.
The results are very interesting indeed.
Methodology
We used a series of data-loggers to record the conditions quite close to ground level. Normal meteorological (general weather) measurements are taken in free air high above ground level. but this does not reflect the conditions in which tortoises actually live or accurately reveal the temperatures that they experience. The reasons for this are explained in another article: 'Can you rely on general climate information to know what your tortoise needs?'.
So, in this case, we located wild tortoises in their natural habitat and placed a data logger in the vegetation cover that they were actually using. This gives a very reliable 'picture' of the conditions experieced 'in real life' over several days.
We automatically recorded both temperature and Relative Humidity every 30 seconds over a 7-day period, a total of 22,000 separate data points from each logger. We also planted ten loggers at each site next to located animals to give a thoroughly representative data-set.
The temperature readings are quite straightforward, but there is a lot of misunderstanding when it comes to interpreting relative humidity readings. There is a massive difference between relative humidity and absolute humidity, for example, as the former is entirely linked to the prevailing temperature. Therefore, if you are unsure about this, please see our detailed explanation 'Understanding Humidity for Tortoise Keepers'.
Results
This a graph generated from a logger placed next to a found tortoise living in a thicket of quite dense wildflower and shrubby vegetation in full bloom.
To make this easier to understand we have overlaid the weather conditions that ocurred during this measurement cycle:
The video (above) provides a very good overview of exactly what the wildflowers and general vegetation in this area consist of during this measurement period.
Dew Point
This occurs in the coldest hours of the night, just before sunrise. Moisture in the air condenses out and becomes dew. It typically evapourates again very rapidly as the sun rises. It can most be clearly observed on car windscreens, for example. It provides a temporary - but important - source of moisture for many arid habitat plants, insects and small reptiles. We did observe Testudo kleinmanni drinking from this dew in Egypt some years ago, though we have not directly observed this with Testudo graeca graeca.
KEY SUMMARY
On dry and sunny days, ambient (air) temperatures 'at tortoise level' peaked between 27°C and 30.3°C.
Tortoises were mostly active when ambient temperatures were between 20°C and 24°C at 'tortoise level'.
Tortoises use basking to further elevate their body temperatures to as much as +12°C above ambient levels when required.
When ambient levels surpassed 28°C 'at tortoise level' tortoises sought retreat in shade.
When ambient levels surpassed 32°C measured in free air at 1.5m above ground level tortoises also sought retreat in shade.
The minimum recorded temperature overnight was 7.2°C.
Even in dense vegetation cover, relative humidity levels during sunny days were very low indeed (as low as 22% in some instances), averaging between 30-50% on typical days, even immediately following overnight rains.
RH rises in the early hours of the morning, just before dawn as the dew point is reached (see above example) and moisture precipitates from the air as dew and ground mists. It also rises just before, during and for a short period following rains. It evaporates very rapidly after sunrise.
Around active tortoises (grazing, etc) ambient temperatures just above ground level tend to be in the range of 20-25°C with a corresponding RH range of 35% to 45% within vegetation cover.
Outside of deep vegetation cover the RH humidity levels during daylight hours are very much lower, typically between 18% and 30% even after episodes of overnight rain.
Even overcast days do not prevent fairly high levels of solar radiation reaching ground level and providing adequate radiant energy for tortoises to easily achieve activity levels via basking.
There was no significant difference between the behaviours of males, females and juveniles under similar conditions.
The main basking and grazing/mating period was concentrated between 9.00am and 11,00am at this time of year. We provide some real-life temperatures and UV readings taken from tortoises during this period. You might notice that the UV-I levels and temperatures are VERY different from what you usually see recommended by those who keep this species in captivity! We'll return to this in a future video...and explain why this matters.
By early afternoon, the temperatures even in April-May are usuallysufficiently high to prompt retreat into shade. On some days certain animals emerged again for a further short activity period in the early evening.
The main 'spring' period is of quite short duration, encompassing March, April and May. By mid-June, or even by the end of May, temperatures will have risen dramatically, and very few of the wild flowers you see here will still be green! By late June, through July, August and September the tortoises will be aestivating (summer dormanct due to extreme heat and lack of food and water), emerging again, briefly in late September through November (though often, there is little vegetation at this time). They will then begin brumation (hibernation) from December through to February-March.
It is important to point out that locations, microclimates and weather vary widely. Weather, for example, varies continuously - it is not fixed. Even localities a few km apart can vary a lot due to altitude, coastal proximity, wind-chill factors and orientation.
Wild tortoises experience a continual shift in conditions minute-by-minute, day-by-day, season by season (as we will see in some upcoming videos and data). One year can be 'dry', another year might experience a 'wet' spring, while others may be 'average'. However, that said, the above 'Key Summary' does provide a really good 'snaphot' of real-life conditions that tortoises in Northern Almeria and Murcia (Spain) experience during late April through early May in a particularly 'good' year for vegetation.
Although this particular video and article does not specifically cover the topic of feeding, do please note that throughout the entire study and observation period from early March to mid-May, not one single instance of a fruit was observed anywhere in any of these habitats. Neither was any available carrion detected.
Contrary to much advice, therefore, Mediterranean tortoises DO NOT either require or even encounter fruit or carrion routinely. We have a detailed article that explains this in depth. IF wild fruits are encountered, this would be limited to a very short period in autumn, not in Spring, but even there, it is incredibly rare to find native wild fruit in most of these habitats (as birds and other animals tend to get there long before tortoises) and even rarer to find evidence of tortoises actually eating it. They will eat it if they find it - but it is just not a typical feature of these habitats. The primary diet is a very wide and seasonally cyclic intake of leaves and flowers as shown in the video.
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(c) 2025 A. C. Highfield/Tortoise Trust
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