DON’T LOSE SLEEP OVER IT

How to fully prepare for tortoise hibernation.

Tortoises have evolved for millions of years to deal with seasonal fluctuations and thrive in periods with less food availability and lower temperatures. These changes in climate naturally slow metabolism in ectotherms and thus hibernation or a ‘winter period’ is an integral influence on tortoise physiology. Although hibernation was a risky process several decades ago, keepers today are much more aware of the potential problems involved in hibernation. Combine this with more reliable fridges, insulated homes and affordable thermometers and the benefits of a dormant period massively outweigh the associated risks. Although it can be a scary prospect, keepers should understand as much as possible about the hibernation process to ensure optimal success.

Which species should be hibernated?

Some of the most popular species of pet tortoises have reached their status because of their tolerance to the UK climate. Many of these come from areas across southern Europe and North Africa and fair extremely well outdoors through most of the year. These are the Hermanns (Testudo hermanni), Horsfield (Testudo horsfieldii), spur-thighed (Testudo graeca) and marginated tortoises (Testudo marginata). All four of these species should be hibernated or at least experience a dormant period. Tropical species such as red-footed (Chelonoidis carbonarius) and yellow-footed tortoises (Chelonoidis denticulatus) will not experience such drastic temperature drops and therefore should not be hibernated. The same applies to popular desert species such as sulcata (Centrochelys sulcata), leopard (Stigmochelys pardalis) and pancake tortoises (Malacochersus torneiri).

Typically, Hermann’s, Spur Thigh "dark-shelled" Ibera and Horsfield tortoises will hibernate extremely well. If they are healthy, they are very hardy species and hibernation is considered beneficial, if not essential for their wellbeing. This would typically happen when temperatures drop below 10°C, with optimal conditions being around 5°C. Eleanor continued: “Horsfield tortoises are some of the most northernly ranging tortoises and therefore require a slightly cooler temperature to hibernate. Anything much higher than about 6°C and the keeper may find that they will scratch away in the box and not go to sleep straight away. In the case of Horsfields', the keeper should aim for 3°C – 5°C. They are also extremely intolerant to dampness, so be mindful that the box must not be damp.”

“Marginated tortoises are not very popular in the UK as they were not imported for very long. However, there are still some out there. Although they inhabit warmer climates than Hermann’s and Horsfield tortoises, they will hibernate. They are also prone to a natural pinkness when they are cooled down. Unfortunately, many marginated tortoises end up on antibiotics unnecessarily as an inexperienced owner or vet may think they have sepsis.”

Pale-shelled spur-thighed tortoises are the most delicate of the popular species. Coming from North Africa, they should only have a period of cooling and not a full sleep. This can apply to Tunisian spur thighs and Western dwarf Hermann's (T. hermanni hermanni) also. There are several other, less popular subspecies which may be more or less tolerant to cooler temperatures and thus require slightly different hibernation periods. If a keeper is unsure of what species they are keeping, it should be a priority that they get absolute clarification before deciding on the length of hibernation, or whether to just offer a cooler winter period.

Health is wealth

Although each species and subspecies will experience different seasonal fluctuations, in captivity a rough estimate on timings can be made. For the three most hardy species (which will be referred to most frequently throughout the feature), Hermann’s, Horsfield and Spur thigh Ibera, hibernation can last anywhere from eight to twelve weeks. Eleanor continued: “At the end of the day, the final decision lies with the keeper. Very elderly and young tortoises should hibernate for a shorter period. This is around two to six weeks. If the tortoise is less than a year old or has never hibernated, the keeper may want to just provide a short one-to-two-week hibernation. This will allow both the tortoise and the keeper to get used to the process. A healthy adult tortoise should be hibernated for anywhere from eight to twelve weeks. I sometimes hear of people who think tortoises should be hibernated for six months and this is not true. They only require a short rest during the coldest months of the year.”

The length of time that a tortoise needs to be hibernated will also vary based on other factors, namely their health. A change in environment or an unclear medical history can produce stress or underline health conditions which may cause problems during hibernation. If a tortoise has recently been de-wormed, it is also worth waiting a while for the gut flora to regenerate before putting them into hibernation.

Ultimately, the keeper must be able to make an informed decision on how long they wish to hibernate their tortoise, based on the animals’ health, breed and age. This will require a good understanding of the tortoise and therefore regular weight checks and health inspections are necessary. “The tortoise should have nice bright eyes, a pink tongue, no sores around its tail or swollen joints” explains Eleanor. “It might sound weird, but the keeper should smell their tortoise and make sure there are no foul smells which would indicate a problem. A healthy tortoise should have clear nostrils and eyes. If someone spends plenty of time getting to know their tortoise, they will have a much better understanding of how to hibernate it.”

Keepers can also do a ‘Bone Density Formula’ which can be applied to Hermann’s, Spurthighs and Horsfield tortoises. This involves taking the weight (in grams) of the tortoise and dividing it by the length (in centimetres cubed). If the bone density ratio is in the range of .20 and .25, the tortoise is a healthy size and possibly ready to be hibernated. Shell deformities can skew this slightly. Eleanor continued: “The bone density formula is a great indicator, but certainly not the deciding factor. I have heard people choose not to hibernate their animals because the formula suggest they are underweight, even though they are healthy and fed well. In this case, it might be a better idea to just hibernate for a slightly shorter period. If the tortoise is really heavy, make sure there is no egg retention. If it is really light, maybe it’s worth a consultation with a vet. But that shouldn’t become an instant reason not to hibernate.”

When?

Choosing when to hibernate a tortoise can be confusing. The weather in the UK can naturally become cooler as early as September, but just because it reaches 8°C in the UK does not mean that it will be reaching these temperatures in Southern Europe and Western Asia. Keepers should try to keep their tortoise awake for as long as possible with artificial heating and lighting indoors once the UK climate falls below 10°C at night and becomes too cold for full-time outdoor keeping. Many keepers aim to keep their tortoises awake until late November. This time frame means it’s usually easier to find natural plants right up until the tortoise needs to hibernate and they can also be greeted with warmer Spring temperatures and lots of fresh weeds when they awaken.

In September/November when the weather starts to cool down a tortoise should be given an indoor enclosure. As this is only temporary, this can be made of a whole host of materials or tortoise tables, vivariums (with the glass removed) and large tubs work great. A basking lamp that provides UVB such as a metal halide or incandescent flood will be necessary to provide heat and light. It is important that the keeper checks their bulbs, or replaces old bulbs at this time. A bulb that has not been used all summer may appear bright, but its UV and IR output may have diminished. Once the tortoise has been brought inside and housed in its new temporary enclosure, it should be maintained at a comfortable 16°C ambient temperature at night and a 30°C basking area for daytime should slowly be reduced. Daylight cycles should also be gradually reduced. For example, if the bulb is on for 12 hours once the tortoise has been brought inside, the keeper should reduce this by a few hours every couple of days