One of the early experimental 'mini-greenhouse' units from 1999-2000 in a sloped, well-drained outdoor pen planted with an edible wildflower seed mix. This was extremely successful but over the following years was developed further, especially when UV-B transmitting plastics became available. Shown here with Testudo graeca cyrenaica.
“Can I keep Mediterranean tortoises outdoors all year round in the UK?” (or anywhere else with a similar climate). The answer is yes – with a few provisos and exclusions. They do need a bit of extra help and your precise location and the orientation of the area will also affect the best way to achieve this. It certainly can be done, however, and in this article we are going to share some of the factors involved in make it work. This is not merely theoretical. It has been (and is being) proven in practice. We ourselves experimented with these methods over 20 years ago, and since then new ideas and materials have come along that make it even more effective and practical, such as the development of UV-B transmitting plastic sheets. We have a great many members on our Facebook Group that are actually using these methods and reporting success.
The fact is that the UK climate is much duller, wetter and colder both in summer and winter (and for longer periods) than in their native habitats. There are some very simple things that you can do however, to make a really big difference. These include ensuring that the substrates/soils are really well drained. This often means adding extra gravel and sand to ‘clay’ type soils. All Mediterranean (and Russian) tortoises need well-drained soils. Kept on too-damp soils they are prone to shell infections (the keratin becomes soft and vulnerable) and also to respiratory infections. In addition, a ‘wet’ substrate interferes with their ability to thermoregulate. So, well-drained slopes (rather than just flat surfaces everywhere) are ideal. Do not believe nonsense that you might read elsewhere that sand or small stones are 'dangerous'. They're not, Tortoises have been doing great on them for literally millions of years. We also maintained several hundred tortoises in captivity for over 30 years using such substrates. Problems? None whatever. Not a single incident.
Another very early example of a mini-greenhouse unit in juvenile pens (in this case for Testudo ibera). One thing that quickly became clear is that the larger the mini-greenhouse unit is, the better, as it creates a more stable internal environment especially with regard to keeping the substrate dry. Later we also used plastic agricultural polytunnel units to achieve similar results on a much larger scale.
By including ‘mini-greenhouse’ type basking enclosures within the areas, you can protect them from excess wind-chill and greatly boost their body temperatures – by as much as +12 Celsius, even on overcast days.
The first ever prototype of the 'mini-greenhouse' which eventually evolved into the far more sophisticated 'Climate Frame' design. This was very basic, easy to construct, but above all - it worked! This one used polycarbonate twin-wall material for the roof (now UV-B transmitting materials are available). It made a tremendous difference to the basking temperatures that the tortoises could achieve on cloudy days (circa 1998).
This makes a huge difference, and because it is solar-powered, it costs nothing to run, either, unlike heat lamps. It also provides a far healthier and more natural distribution of infra-red. You can now use UV-B transmitting plastics for this, and again, the tortoises will receive a very good (more than adequate) exposure of UV-B naturally, without needing fluorescent tubes.
Examples of dry, sandy substrates inside large mini-greenhouse and 'polytunnel' units: tortoises both brumated (hibernated) and aestivated in near-natural conditions inside these areas. They could dig down under the succulents and cacti easily.
In some areas we also mixed in bark 'mulch'... and maintained a very slightly higher substrate moisture level. These areas proved very popular as nesting sites. We bred many quite challenging species in these environments. It is very easy to adjust soil moisture - just add some timed drip irrigation if it is desired to raise the levels.
Is it possible to avoid all use of artificial light and heat sources in a location like the UK?
The answer to that is "It depends". It certainly IS possible with the right type of housing units in a suitable location. We had south-facing slopes, no buildings or trees close by to shade anything, and an unobstructed view of the sky. In a more shaded or partly enclosed area it will be much more challenging. Also, in a particularly 'bad' year in terms of weather it will be far more difficult than in a 'good' or 'average' year. In these circumstances you might indeed need to supply some extra artificial basking heat - but you will need much, much less of it with units like these than if no such units are provided. That saves a huge sum in ongoing energy costs and greatly reduces exposure times to the damaging effects of artificial heat sources, and all artificial heat sources have some quite serious side-effects.
Few people realise this, but lamps such as Mercury Vapour 'UV-Heat' basking sources and IR ceramic emitters were primarily developed for use in industrial drying cabinets and in paint curing processes.
They were not originally intended to be used with live animals. They only subsequently began to be marketed for this purpose. Look for an updated report on this coming soon. As always, take accurate measurements and adjust the methods described here to suit your own individual location and circumstances. There are some practical examples of how people can add some supplementary heat (if required) on our FB group.
The 'controlled environment' approach
There are fundamental differences in the philosophy and practical approaches to keeping tortoises and other reptiles between those who advocate 'naturalistic' methods and those who believe in an almost entirely 'artificial' approach. These differences are profound. It gives rise to a great deal of misunderstanding, and confusion, in people who are simply looking for rational and practical advice.
Among those who keep tortoises in captivity you sometimes hear those who promote artificial methods claim that nature is a 'harsh' place and that they can do far better by keeping the animals confined in a so-called "optimal" environment all year-round. No need to hibernate/brumate.. no need to estivate to escape 'harsh' conditions, but constant provision of heat and a constant supply of food 365 days a year. This idea can appeal to beginners, and those who have no real understanding of how these animals evolved INTO these natural habitats and how their biology and metabolism is intimately linked to the conditions found there.
Unfortunately ideas like this are very common among uneducated 'pet keeper' groups. They really do believe that they are providing conditions that are superior to those that nature provides. They even claim in a very misleading way, that mortality rates in the wild are very high. The truth, of course, is very different. While there can be high mortality rates in nature, especially among juveniles, this is due to predation (often by introduced predators), habitat loss, and roads. Losses directly related to the environment tend to be absolutely minimal. These animals are 'geared' to experience (and thrive) in often very cyclic, sometimes harsh environments. They achieve excellent health and perfect growth under these conditions. If you instead 'force' constant feeding and continual activity growth problems inevitably manifest, along with a number of other problems that longer-term are likely to shorten life and lead to poor health (e.g., renal and liver disease). We have previously posted the results of such an approach upon bone density.
Nowhere is this fundamental difference in philosophy better illustrated than by advice from those who promote these totally artificial methods to not even allow juveniles any time out of doors until "2 years of age" or some other arbitary period such as "1 hour for every inch of shell growth". There is absolutely zero credible scientific basis for this bizarre advice. It is entirely irrational, yet is believed and put into practice by many.
Juveniles maintained 100% outdoors in secure pens with mini-greenhouse units to provide dry areas in wet weather and to greatly elevate their ability to raise their body temperatures. Growth with these tortoises was outstanding. Zero 'pyramiding' or any other form of metabolic bone disease. Claims that juveniles need to be kept exclusively or mostly indoors are completely false. Many other keepers can confirm identical results.
A juvenile Testudo marginata (Marginated tortoise) shown at 3 years of age after being captive-bred by the Tortoise Trust and having been raised in a combination of outdoor pens, polytunnels and mini-greenhouse units as described here. The growth here is indistinguisable from a wild example. Brumation and aestivation ocurred from year one within the units. No artificial lamps were ever used. No 'humid hide boxes' were ever used either. This is yet another common misconception.
One other area where entirely false beliefs are common is that we can provide 'equivalent' or even 'superior' quality of light and heat in captivity to that which they experience in the wild. It is true that in terms of UV-B lighting, for example, some really good advances have been made in recent years. These are much better in terms of UV-B and UV-A provision than what was available years ago. They are still not a match (and certainly are not superior to) natural sunlight, however. Heating remains a very major problem area. The infra-red spectrum of artificial sources in general use by keepers in NO WAY approximates that of solar radiation, and it can have extremely negative effects upon living tissue exposed to it. For one thing, instead of true 'deep penetration' most such sources 'dump' large amounts of energy at skin-depth, where they have an intense dehydrating effect as they act upon water molecules. By contrast, natural solar Infrared is WATER FILTERED as a result of it passing through the atmosphere. Here, damaging parts of the radiation spectrum are absorbed and diminished by water molecules in the atmospheric layers. It therefore does not act with similar ferocity upon the water molecules of the animal's tissues. It is no surprise that we find the highest incidence of problems with bladder stones in captive reptiles in those animals that are maintained indoors in close proximity to sources of artificial heating.
Compare the results of basking under artificial heat lamps (first two images) with basking outdoors under natural, unfiltered sunlight. Instead of localised over-heating with the bulk of the animal still remaining too cold, natural basking results in very even, all-round warmth. This in turn assists with the efficient conversion of sterols via UV-B to produce vital vitamin-D3. It also effects digestion and many other critical aspects of the metabolism.
Further, the wavelengths from the sun involved are much more penetrating (typically >5mm beyond the dermis vs <1mm for typical artificial sources), providing a very wide, very even, and very safe all-over warming effect. This is very critical of course for herbivorous reptiles, that rely upon this to produce vitamin D3 from UVB, a process that also requires heat. To those who might believe that they can easily provide this kind of heat in captivity artificially, we say "No. You can't". It is very challenging indeed. This is a very high profit area for the so-called 'pet industry', however, so it is no surprise that both unsuitable prepared foods and unsuitable accessories are so heavily advertised and promoted.
To date NO artificial heat source that we are aware of is equivalent to what happens in the natural habitat. We can learn from nature, and we can attempt to get as close as possible to it, but if we are foolish enough to believe that we can 'defeat' it or are able to provide 'better' than what nature achieves we need to think again.
The reality is much more complex and simplistic beliefs otherwise are soon revealed as fallacies when examined carefully. That was the basis for the design of the 'Climate Frame' terraria.
There is, of course, much less profit to be made from promoting 'natural' methods that do not require the ongoing purchase of expensive lighting accessories or from promoting more natural, self-grown or foraged diets. This is certainly one reason why there is so much 'trade' resistance (and from people and groups associated with the trade, through sponsorships, etc.), to moving away from these outdated 'artificial' methods based upon false and misleading claims.
Principles of enclosure design
Whether indoor or outdoor, the habitat should be as interesting as possible. Provide an open area for basking, a heavily overgrown area for retreat, and a variety of rocks and native plants for cover, decoration and possibly even for grazing. Juveniles do not have any different temperature, light and humidity requirements from adults. They do, after all, hatch into the exact same environment as adults in the wild. Provided they are protected from predators and accidental injury they should therefore be treated identically.
A Testudo ibera shelters on a hot, sunny day under scrubby vegetation in one of the outdoor pens. Provision of shaded areas is critical, as even in the UK tortoises can overheat on hot days in summer. If you did not know differently, this photo could have been taken in the natural habitat. This is the very essence of good enclosure design.
Tortoises in the wild from temperate zones live in very extensive, and very complex environments. There are hourly, daily and seasonal changes in temperatures, humidity and light levels. The seasonal changes in vegetation are profound. Almost nothing is 'constant'. Again, this exposes dated views that tortoises have a single, fixed 'optimal' temperature requirement. They do not (though some rainforest species experience far fewer variations). In captivity, when designing habitats, an excellent source of inspiration is to visit the natural habitats in person, or if this is not possible, at least carefully study photos of natural habitats and try to replicate these as closely as possible.
Testudo hermanni boettgeri basking in well-drained open areas in one of the sloping outdoor pens (Wales, UK). They have no problems with substrates containing sand, and no, they do not choke on or get impactions from stones either. If they did, this species would be extinct as such substrates are everywhere in their natural ranges.
It is also a good idea to provide for ‘natural’ burrows and burrowing in these sloped enclosure. Tortoises will retreat there if the weather is bad, or if it is too hot. This is exactly what they do in the wild. They do not necessarily need to feed every day, nor should they be expected to (this is one of the main causes of dangerously accelerated growth in captivity, a direct cause of metabolic bone disease).
A naturally excavated burrow is visible in one of the pens shown here. Can you spot it?
Testudo horsfieldii (Russian tortoise) rests at the entrance to his burrow.
You can also create semi-artificial burrows into sloped areas quite easily. We made this one by sinking an upturned plastic container into the bank.
You can just seen part of the plastic container here, off to centre-left. This proved dry and popular during episodes of extended rain.
Brumation (hibernation) and Aestivation
These are important processes and are a critical part of the annual activity cycle of many species. They prevent excess growth and greatly affect hormone levels, for example. Depriving them of this tends to accellerate growth (with consequent high levels of metabolic bone disease). The longer term effects are more difficult to quantify but are unlikely to be insignificant.
We found that Mediterranean tortoises can manage both for themselves outdoors very effectively PROVIDED that a sufficiently dry substrate is available. Indeed, many tortoises in the southern parts of the UK have done this for many, many years even without mini-greenhouse type units or special effort put into creating optimal substrates. The famous 'Timothy Tortoise' of the 18th C. naturalist Gilbert White was one such example. This tortoise managed it all very well indeed, outliving it's even more famous owner. There are many such examples. We are aware of some that have done this successfully every year for six decades or more.
HOWEVER, this is highly subject to soil type, drainage and general weather conditions. As such it cannot be widely recommended. Very few tortoises in the north of England or Scotland, for example, are known to have survived like this.
In a large, sheltered polytunnel or mini-greenhouse (or even a regular greenhouse) things are much more controllable. Here, the substrate and drainage can be managed, and temperatures moderated. Today, a range of remote sensing thermometers makes monitoring such units easy, no matter where you are. Many of these devices employ an app on your smartphone. We strongly suggest thoroughly testing the units over a 12 month period using such thermometers and (preferably, data loggers) so that you are fully informed as to the variations that can occur. Also monitor for flooding or excessive dampness. This is especially important if you are hoping to use such habitats for 'natural' type brumation/hibernation. Test it extensively under a variety of weather conditions first.
To maintain adequately low levels of soil moisture, and to provide maximum temperature stability, the larger the covered area the better. It is often impossible to prevent water seeping via the perimeters in very small units. The units that we used for this purpose were several metres long by at least two metres wide (some were four metres wide).
Here is some movie footage (no sound) of one of these plastic polytunnel units in use with tortoises preparing to bury down. They did this for both their brumation (hibernation) and aestivation cycles. It does give a very good idea of just how warm and dry such housing can be (the cacti flowered regularly):
Opuntia cacti flower in a polytunnel tortoise habitat - In Wales, UK!
One interesting effect that can be measured when testing temperatures just below the surface where tortoises bury down is that even on cloudy days there will be a substantial 'peak' in these subsoil zones. The temperatures are certainly not constant as they are, for example, in refrigetator hibernation/brumation. This does not distrupt the process in any way, however, and if we look at readings from these same species in their natural habitats, we observe the very same thing. In fact, here is a data-logger recording taken next to a buried wild Testudo graeca graeca.
Typical fluctuations in temperature during brumation recorded in the natural habitat at a depth of 10cm. The difference between day and overnight temperatures is significant.
Standard greenhouses (with adjusted substrates) being used as 'natural' brumation (hibernation) units. This site was very well drained.
Examples of tortoises using the substrates in greenhouses and polytunnel units for self-managed brumation and aestivation.
Pens can also be planted with edible wild-flower mixes. This makes for a fantastic quality diet, not too far removed from what they experience in the wild. There are even special ‘tortoise seed mixes’ available. The pens you see here were planted with one of those. This results in a very healthy diet that requires no supplemental feeding, and lasts all season. Click for enlarged images.
Evolution of the pens: Initially, the area, though sloped, had a very heavy, clay-rich soil which was covered in grass. This was far too wet and not suitable. This problem was solved by removing much of the clay soil and replacing it with several truck loads of sand and light gravel mixed with some of the original soil. This greatly improved drainage and made it suitable for the cultivation of mediterranean wild flowers. No supplementary feeding was required from March through to October.
One of the several different varieties of 'Tortoise Seed Mixes' now widely available after being established for 2 years. After the first year, they self-seeded in subsequent years.
Tortoises raised on this diet, in the type of housing shown do not have deformed shells, metabolic bone diseases, or any of the other serious health problems we sadly encounter so often.
Another view of the planted pens with varied cover, open spaces and well-drained slopes. Overnight shelters were provided in addition to 'burrows' and tortoises could select which they preferred.
A North African Testudo graeca grazes on vegetation within the enclosure. Again, no, it is in no danger from the small stones...
From 1990-2008 we ran a large ‘reception’ centre for rescued tortoises in Wales, UK. These are some of the units and areas that we set up there. At times, we would have several hundred tortoises ‘in residence’ at any one time. There was always strict biosecurity, as we received many animals that were victims of the illegal trade and which could be carrying a variety of highly contagious or infectious diseases, including viral diseases. These were kept in strict isolation in a separate hospital building, not shown here. In addition to these pens, there were some ‘dry’ greenhouses and a ‘dry’ polytunnel unit. Tortoises both brumated/hibernated and aestivated in these – again giving them ‘rest’ periods from continual food consumption and sparing them excess rates of growth. Over 18 years there was zero mortality, despite large numbers of tortoises being involved every season.
There was also a heated ‘tropical’ house that held a variety of equatorial species, though these too were allowed out when weather permitted.
Juvenile pens were all covered with various types of secure mesh to protect from predators (rats, foxes) and each also included it’s own ‘mini-greenhouse’.
Anti-predator monitoring of the area and all pens was continual, with live-catch traps placed around the site and continual observations were made.
We also maintained some excellent rodent deterrents - several large cats!
The ever-vigilant 'Thomas' - one of the anti-rodent patrol!
There are many variants that no doubt you can think of or develop from these basic designs and ideas, but we hope it shows you that yes, it is possible and it really can provide a very high quality of life to captive tortoises. Much better than a tiny enclosure indoors. The only limit is your imagination, but it is also worth noting, that with sky high energy costs these days, some up-front investment in housing systems like this can save you an absolute fortune, long-term, in reduced energy inputs, in addition to being vastly superior in terms of a healthy and rewarding environment for your tortoises.
Q&A
Does this mean that you now recommend outdoor brumation (hibernation) over traditional box type hibernation or refrigerator hibernation? Which is best?
No. There is no universal 'best' method. All of these have very good records of effectiveness and safety IF CORRECTLY IMPLEMENTED. What will be most suitable depends almost entirely upon your individual circumstances, facilities and location. You need to review and understand pros and cons of each approach carefully and decide which is the most appropriate for you. We have tested all of these over many years and continue to recommend them all where appropriate.
I have made a 'frame type' outdoor unit but it seems to stay far too damp and humid inside. What is going wrong?
Usually, that moisture is seeping in under the sides, and that there is a lack of side-ventillation. It can also take some time for things to dry out fully and to stabilise. A lot depends on how saturated the soil is surrounding the unit. If this continues to be a problem you may need to dig a trench anound the unit and seal this with a buried water-proof membrane, such as strong polythene. Add pebbles, and if possible, a drainage pipe to a lower level over this. Sometimes expermentation is required as every location is different.
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(c) 2024 A. C. Highfield/Tortoise Trust
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