Hibernation is one of the things owners most commonly get wrong when looking after their tortoise, sometimes with fatal consequences. If your tortoise is one of the breeds that requires hibernation (not all breeds hibernate), then this will be a subject you'll need to know well.
Firstly, it is important to ensure that your tortoise is completely healthy before attempting hibernation. If you are in any doubt, then 'over-winter' your tortoise instead (see below). While the Mediterranean tortoises hibernate, not all species of tortoise do - research whether of not your tortoise is a hibernating species in advance.
By the end of August your tortoise should be 100 per cent healthy and the correct weight if he is to go into hibernation. The Jackson’s Ratio Graph can be used to check the weight of Mediterranean tortoises, you can find out more about the ratio by clicking here. If your tortoise is not up to the correct weight by this time, do not hibernate. Remember to check all the other signs of health too. If your tortoise's state of health is in any doubt at all, do not hibernate and seek veterinary advice instead.
What temperature should you keep your tortoise at during hibernation?
It is essential that the temperature where your tortoise is hibernating is kept around 4–5°C . A couple of degrees above or below the ideal will be okay for a short amount of time only.
Never let your tortoise become exposed to near freezing temperatures. Temperatures below 2°C can cause eyes problems and blindness, any lower and your tortoise could freeze to death.
Keeping the temperature below 8°C will ensure he does not stir from hibernation early. When the temperature reaches 10°C the metabolic changes that allow for hibernation are reversed and a chemical called glycogen is released into your tortoise's system to boost energy levels. He must eat before this boost is used up. This boost will only occur once, so if your tortoise stirs early he must be allowed wake up. NEVER attempt to put him back into hibernation.
Set up your hibernation area well in advance and check the temperatures every day at different times with your thermometer to ensure that you're able to sustain the ideal temperature. Using two thermometers will provide a more accurate reading. Once your tortoise is in hibernation continue to check temperatures regularly.
The ‘winding down’ procedure
This process can take anywhere from three to six weeks depending on your tortoise's age and size. During this period DO NOT feed your tortoise anything. By the time your tortoise reaches hibernation there should be no undigested food left in his stomach as this can rot during hibernation, causing asphyxiation due to pressure build-up on the lungs.
From week one, don't offer your tortoise any food - even if he looks hungry, do not give in! If he begins to eat his bedding replace it with towels to prevent this. Continue to provide light and heat for your tortoise for 12 hours as normal so he can digest the remaining food in his system. Bathe your tortoise everyday in warm water to encourage drinking.
During the second week, reduce lighting gradually down to eight hours and continue daily bathing. Your tortoise will have slowed down quite dramatically by this point and will be hiding away a lot. During this week, monitor faeces production. If your tortoise continues to defecate regularly, continue week two’s care pattern for up to two more weeks, until faeces production slows. Do not reduce the heat and light levels further until faeces production has slowed. Without a good amount of light your tortoise will be unable to complete digestion of the remaining food in his system.
During week three, bathe your tortoise on alternate days, reducing the heat times down from eight to four hours. At the end of week three, turn off any background heating and place your tortoise in a cool but frost-free room. Bathe your tortoise for the last time a couple of days prior to the end of the week and ensure that he is fully dry. If no faeces are produced during the final bath, continue without heating for a further two days in the cool room. The temperature should be no higher than 10°C but not below 3-4°C. On the last day move your tortoise to his hibernation area. If faeces are passed during the last few days, leave him in this area for an additional two to three days. Juvenile tortoises generally require a shorter wind-down period so the above process should be followed but reducing the time from a week to five days.
What is 'over-wintering'?
'Over-wintering' refers to keeping a tortoise in artificial surroundings during the winter. It is needed when tortoises are unfit for hibernation due to health issues, their age or when the hibernation process has been stopped early. During over-wintering, adequate light and heat is important to ensure your tortoise is able to continue normal bodily functions. Over-wintering is best done in a large plastic box or indoor play pen, depending on the age and size of your tortoise. The humidity will need to be carefully monitored so your tortoise does not dry out, and he will also need regular baths.
Adequate lighting and heating will be required. Lights should be turned off at night to create a natural light cycle, but additional heating may be needed to maintain an ideal night-time temperature above 15°C.
Continue to provide a nutritious balanced diet during the winter period.
Ways to hibernate your tortoise
The box method of hibernating your tortoise is the most popular way to hibernate.
You will need:
- Two sturdy boxes - one small enough to fit inside the other with a 2 to 3-inch gap around the edge. They should be made of wood or substantial cardboard.
- Substrate - the 50/50 sand to soil combination is best.
- Insulation - polystyrene blocks or balls are best but shredded paper can also be used.
- Thermometers and alarms - you will need good quality, accurate thermometers fitted with an alarm to alert you if the temperature falls or rises above a set temperature range. A second thermometer that you can use to compare is also useful.
Place the smaller box inside the larger one and pack in your insulation - there should be around 3 inches of insulation around the inner box on all sides - then add an additional layer of polystyrene to the floor (tortoises dig down in the cold so it's important that the base is kept warm).
Choose an hibernation area where you will be able to maintain the ideal temperature of 3-7°C, a garage, shed or outbuilding is normally ideal. Ensure that your box cannot be chewed by rodents.
The inner box should allow enough space for your tortoise to turn around if required. After the winding down period, place your tortoise in the box on the substrate, and pack more in around him so he seems comfortable. Place your thermometer probes inside with the tortoise and put the display where it can easily be seen. If the thermometer has an alarm, set this accordingly. Create air holes in the top of the boxes for ventilation.
How long should I hibernate my tortoise for?
Adults tortoises benefit from at least 12 weeks of hibernation but not more than 18 weeks, as his own reserves will not sustain him for longer than this. Juveniles should be hibernated for slightly less time than this - ideally between 8 to 12 weeks.
Checking your tortoise during hibernation
Your tortoise should be checked over physically every week - you will not harm a hibernating tortoise by handling it.
As well as checking for all the normal signs of good health you should also pay close attention to your tortoise's body weight. He should lose around 1 per cent of his body weight per month during hibernation. Take note of his weight the day he goes into hibernation and then monitor this closely. If he is found to be losing significantly more than 1 per cent per month, wake him from hibernation immediately and over-winter him instead.
Look for any signs of faeces or urination; passing faeces in the first few weeks is not a particular worry but if there are signs of urination, your tortoise should be woken immediately. Urination during hibernation can lead to acute dehydration, which can be fatal.
If you can hear your tortoise moving around, particularly if the temperature has risen suddenly, check that your tortoise has not woken up. If he has, follow the process of waking him up – do not let the hibernation continue.
Waking up a tortoise from hibernation
When you decide the time is right to wake your tortoise, move his hibernation box into a warm area and take the lid off the box, after an hour or so you should hear your tortoise start to move. When he does, place him in a bright environment near his basking lamp. Allow him to find his own way under the lamp to avoid shocking his system and so you can see that he is moving freely and that he will be able to move away once he has warmed up.
Once warm, check your tortoise for the usual health signs and bathe him in warm water to help him to replace fluids for around 20 minutes. Repeat the process twice a day for the first few days. If your tortoise has been woken due to urinating during hibernation then bath him before basking as his hydration levels will be low.
After the first bath, food can be offered. Many will start eating within the first 24 hours, often sooner. Offer your tortoise's favourite food to encourage eating. If your tortoise has failed to start eating within a week of waking, seek medical advice immediately.