Real-Life Temperature and Humidity Readings in the Natural Habitat of Testudo graeca graeca in Early Spring.
- tortoisetrust
- 7 hours ago
- 5 min read
A. C. Highfield
We recently published a very comprehensive article that sought to correct some of the many false "facts" and misleading claims about what levels of humidity wild tortoises really experience in their natural habitat: How do Hatchling and Juvenile Mediterranean Tortoises Really Behave in the Wild and What Humidity Levels do they Really Experience? Myth Busters Episode 12. The internet and social media is full of grossly inaccurate claims and advice on this subject. Why does this matter? It matters because people then attempt to replicate these fictitious conditions in captivity, believing them to be a fair representation of natural habitats, but in reality subjecting the tortoises to dangerous and harmful temperatures and moisture levels.
The negative effects of keeping arid habitat tortoises too damp, for example, include softening and weakening the keratin of the scutes, the claws, the beak and the skin, and making these far more susceptible to fungal and bacterial pathogens. In turn these pathogens may be inhaled, with consequent respiratory diseases occurring, including pneumonia and a persistent nasal discharge. Some of these conditions can prove very difficult to treat and frequently have fatal outcomes.
There is also a tendency in many captive situations to force excessive temperatures upon tortoises, and to "blast" them with excessive levels of UV-B. We will return to the issue of appropriate levels of UV-B in a future article. As with many things, more is not always better, and keepers do need to realise this. That applies to feeding amounts, UV-B, temperatures and certainly to humidity levels.
The best guide we have are levels actually experienced by these species in the wild. These levels should not be obtained through speculation and guesswork, but by careful and methodical measurements over an adequate period of time.
As a further example, here are levels recorded over several days taken with precision data loggers with valid calibration certificates.
This is a 7-day cycle of temperatures only recorded at the exact same location. Overnight temperatures reached a minimum of 4.3 Celsius. The first half of the week was cloudly and overcast, but tortoises were still observed basking and one individual basking in an ambient air temperature of 17 Celsius was recorded with carapace and plastron temperatures of 28.3 and 27.4 degrees Celsius respectively. This is another aspect where solar infra-red radiation differs substantially from IR produced from artificial sources. It has vastly superior 'deep heat' and even heating characteristics upon living tissue. See our specific article on this: How Heat Lamps can Harm the Health of Tortoises and Contribute to Growth Deformities.
Heat lamps and solar warmth are two totally different things. Despite extensive marketing hype from the 'reptile industry' artificial heat lamps behave in completely different ways to the sun and affect animals subjected to them in measurably different ways.
Key facts:
The lowest overnight temperature recorded was 4.3 Celsius. This is important as it is frequently claimed that Mediterranean tortoises require "warm" conditions overnight. They do not. We have covered this previously. They also rely upon these reduced levels to slow up their digestive tract and metabolism on a cyclic basis. In turn, this has important implications for avoiding excess growth and achieving good bone density. See: Unnaturally High Growth rates in Tortoises: Causes and Consequences. If they are kept too warm overnight the result is rapid growth with a high risk of deformity and "pyramiding", together with other severe effects upon their digestive processes. Despite this entirely compelling evidence being made available for several years now, misleading and dangerous nonsense continues to be repeated as "fact" all over social media.
Relative humidity levels during daylight hours and at tortoise activity temperatures are consistently far lower than most keepers assume. For example, minimum RH tends to occur in the early afternoon, and can be as low 16.4% as recorded here. This is, remember, actually measured WITHIN fresh spring vegetation. In open, non=vegetated patches it is even lower, sometimes into single digits. Average RH levels during tortoise activity range from 25% to 45%.
Genuinely high levels of RH occur only during or shortly after episodes of rain, and also overnight, in the coldest hours just before sunrise. Here, they can surpass 90%. It is critical to understand how humidity is measured, however, and what this really means. Relative humidity is different from absolute humidity. Do not just assume that 90% RH is the same thing regardless of the prevailing temperature. We have an excellent explanatory article on this subject: Understanding Humidity for Tortoise Keepers
This is a very dry, semi-arid habitat, even after the wettest winter for decades.
Tortoises tend to be active in two phases at this time of year. Early mornings when they bask and graze for an hour or two, retreating at temperatures rise later in the morning and early afternoon, then again late in the afternoon as temperatures reduce. They are rarely active during the hottest periods of the day.
The habitat in question is also shown here. This was the wettest winter and early spring in this locality for over 30 years as already mentioned. We located a number of adults, both male and female and also several juveniles, from last September's hatching to 4 or 6 years of age in this very habitat and the sensors were placed the exact locations where tortoises were active. We can therefore safely rely upon these measurements as entirely representative of the true conditions this species experiences in nature.
It is vitally important that keepers gain accurate knowledge of wild habitats and the conditions prevailing in these habitats. Without this, there is no reliable benchmark to use as a guide when maintaining various species in captivity, Getting this wrong invariably has negative consequences. We should learn from nature and never fall into the trap of believing that we can improve upon it.
As you can imagine, conducting genuinely original research like this takes a very long time to conduct (months and years), involves a great deal of travel, is very time consuming, and also requires the use of some very expensive equipment indeed. If you would like to see more of this, we really would appreciate it if you could make a donation or subscribe. It really helps. We have been established since 1984 and we continue to provide original research and reliable information to tortoise and turtle enthusiasts worldwide. We also have two excellent online courses available, one for beginners and new keepers and one for advanced and professional keepers. These cover some of the background science that is key to truly understanding and appreciating tortoises and turtles and are also extremely practical. We have taught in colleges and universities around the world, and have trained private enthusiasts, wildlife rangers and conservation staff for many years.
All text & photos: (c) A. C. Highfield/Tortoise Trust
Comments