The Hermann's tortoise is a hibernating species of tortoise. It's important for them to hibernate as it helps maintain a slow even growth rate. Being overwintered substantially increases the amount of food eaten possibly leading to rapid growth and resultant metabolic bone disease. There are times when a tortoise should not be hibernated. These are:
Having an ill tortoise or following a period of being unwell;
Having owned your tortoise for less than a year;
Having an underweight tortoise;
The lenght of hibernation depends on the size of the tortoise. A large adult may be hibernated for up to 16 weeks. A very small tortoise around 8-10 weeks.
Preparing for hibernation
Towards the end of August is a good time to start assessing whether you think your tortoise is fit and healthy enough to hibernate. The first thing that needs to be checked is its weight. A tortoise needs to have built up sufficient fat reserves to survive the hibernation period. This fat reserves not only provides the energy they will need but also water to prevent them becoming dehydrated. The easiest way to check that your tortoise is at the correct weight for safe hibernation is to refer to the Jackson Ratio Graph. You will need to accurately know your tortoise's weight and length for this. See our section on general care to learn how to correctly measure the length of your tortoise. Also a full check of eyes, ears, mouth, nose, tail, shell and general body appearance needs to be carried out and repeated in the lead up to the 'wind down' period. You are looking for any abnormalities, swellings, lumps or discharge - anything that may indicate your tortoise is not 100% healthy.
The Wind Down Period
In the wild hibernation is preceded by the days becoming shorter and cooler so that the tortoise becomes less active and less interested in food until it stops eating. This is what we refer to as the wind down period. In the UK as our summer season is shorter, this would happen too early in the year, so you will need to artificially keep your tortoise awake by providing extra heat and light. However, you will then need to initiate a wind down period. The timing of this will depend on the size of your tortoise. The larger the tortoise the longer wind down period they will need. Essentially wind down means slowing your tortoise down using cooler temperatures and less light so that it becomes less active and stops eating, but still awake and warm enough so that it can digest any food remaining in the gut. It is recommended by the Tortoise Trust that a temperature of 13c is low enough to stop a tortoise from feeding and moving around too much but still high enough to allow digestion. Although gut transit times vary from tortoise to tortoise the Tortoise Trust also recommend the following fasting periods:
Large Tortoises (2-3kg) fast for 1 month
Medium Tortoises (1-1.5kg) fast for 3 weeks
Small Tortoises (less than 1kg) fast for 2 weeks
Although no food should be offered during wind down, it is important that your tortoise should be bathed 3 or 4 times per week and allowed to drink to prevent dehydration.
The Fridge Method of Hibernation
Once your tortoise has been through the wind down period and is inactive it is time to hibernate him. The fridge method of hibernation is becoming a very popular way to hibernate tortoises because if done properly is very safe. Although it sounds strange to put your tortoise into a fridge there are several advantages over the box method or natural hibernation in the ground.
Firstly it is easier to maintain a stable temperature in a fridge. If the temperatures become too low frost damage can occur. This can lead to death or blindness. If the temperature rises to high the tortoise can become too active and quickly use up its energy reserves which again can lead to death. Through careful testing and monitoring it is fairly easy to maintain a constant temperature in a fridge and to easy to take action if the temperature should vary.
Secondly, there is no risk from predators finding your tortoise whilst it is hibernating in the fridge and harming it.
Finally, it is easy to check on your tortoise in the fridge to monitor weight and where it has urinated or not.
Preparations for the fridge method do need to begin several weeks or even months earlier. First of all a suitable fridge is needed. Never use your domestic fridge used for food storage or an old faulty one. Fridges without freezer compartments are best. Your tortoise will need to go inside the fridge in a container that is big enough for your tortoise to turn around in (we use plastic food storage boxes that have air holes drilled into them). The fridge will need to be big enough to house this container. You will also need at least two thermometers one of which should be placed onto the substrate next to the tortoise and the other to measure air temperature. Some weeks before your tortoise goes into the fridge you need to test it using your thermometers to ensure that the correct temperature range can be maintained. The ideal temperature for tortoise hibernation is 5c. If temperatures get too low and reach 0c frost damage can occur, this can harm or even kill your tortoise. If the temperature becomes too high (10c +) your tortoise can start to wake and move around using up vital energy stores. Putting full water bottles on empty shelves inside the fridge to add thermal mass will help stabilise the temperature. Once you are happy that your fridge can maintain 5c and your tortoise is properly wound down, he can be placed in his container in the fridge. Wooden, plastic or even cardboard boxes are all fine to use but must have ventilation holes in them. A lid is useful to stop any waking tortoises climbing out. The container needs to have a substrate that your tortoise can burrow into. We use the same 50/50 topsoil and play sand mix we use in our tortoise table. Another alternative is shredded paper. Ensure that the container is placed centrally on any shelves and is not in contact with the sides of the fridge which may be somewhat cooler. We normally open the fridge door very briefly a couple of times a day to refresh the air inside. You will also need to check that your tortoise hasn't urinated. If this does happen you will need to wake your tortoise as he could be at risk of dehydrating. Around once a week, throughout wind down and hibernation check your tortoise's weight. It's normal for around 1% of body weight to be lost, much more than this and you should wake your tortoise. Should your tortoise wake during hibernation, get them up and keep them awake. Never put them back into hibernation.
Waking Up From Hibernation
First of all take the hibernation box out of the fridge and place it in a warm bright area. You should see your tortoise starting to wake up fairly quickly. After about an hour take your tortoise out of the hibernation box and put him where he has access to a basking lamp with a temperature of around 30c. Don't place your tortoise directly underneath the lamp but just a short distance away so he can walk to it himself. It's really very important that your tortoise is able to warm itself. Without this additonal heat and light their normal feeding instinct will not kick in. A warm room in your house is not sufficient as they need to bring their body temperature up to 30C. It's also very important to bath your tortoise within a couple of hours of waking so that they can drink and re-hydrate themselves and to repeat the bathing daily or even twice daily for a week or two. With adequate heat and light your tortoise should be feeding within 24 hours and should of definitely taken place within a week of waking. If your tortoise is not eating do not be tempted to place them back into hibernation as they will not have the energy reserves to survive. Instead increase heat and light and if this fails seek help from a reptile specialist.