HIBERNATION

The benefits of hibernation

Hermanns tortoises like most of the Mediterranean group are biologically programmed for an annual hibernation period. It ensures that tortoises are not eating for 365 days a year and so encourages slow natural growth. To artificially keep a tortoise awake all year would increase the food intake to at least double the safe amount, this would lead to abnormal growth and cause metabolic bone disease, leading to lumpy shells. It would also put immense strain on the renal system as utrate production would be over increased, this leading to kidney or bladder stones and eventual death.

Therefore, if you want healthy Hermanns tortoises make sure you hibernate them and hibernate them correctly!

For most new and inexperience tortoise keepers the thought of hibernation instils a complete panic, brought on by a fear of accidentally killing their pet tortoise. However, times have moved on and we now have the knowledge to safely guide our tortoises through a much needed  hibernation. The plusses of hibernating far out way the minuses of not doing so.

The mistakes made by most people hibernating many years ago (and unfortunately still a percentage today) were to either:

(1) Hibernate a tortoise that was suffering from an illness or is under weight

Like the rest of a tortoise's metabolism the immune system also dips when hibernating. Any slight ailment that the tortoise may have will only get worse when it hasn't got it's normal aggressive immune system that a warm, active tortoise has. A Hermanns tortoise who is under weight re: the 'Jacksons ratio' should not be hibernated. An under weight tortoise  may be a sign of an undetected illness or has simply not put on enough fat reserves to carry it over the hibernation period.

(2) Feed the tortoise just prior to hibernation.

A tortoises metabolism when in a state of hibernation is almost completely shut down, its heartbeat slows down to virtually nil, its senses shut off and its bodily functions also cease including digestion this is the key factor here. Any food which is therefore inside the tortoise's gastric tract will not be digested and simply rots. This in turn causes severe internal problems from the gasses produced from the rotting food.

(3) Hibernate at temperatures above 10*c

A tortoise has an inbuilt mechanism which tells the tortoise to wake up when the surrounding temperature reaches 10*c. In their natural environment they will have buried into the ground where the temperature remains a fairly constant 3 to 7*c over the winter period, only reaching 10*c with the onset of Spring. At 10*c a chemical reaction happens inside the tortoise a massive release of glucose from the liver glycogen is released  and flushed into the blood stream. This gives the tortoise an initial energy boost sufficient for it to start moving, basking and eating again. However a tortoise has only so much of this energy boosting product available, so when in artificial hibernating situations where the temperature is often allowed to rise to 10*c and above the tortoise will have to use up it's supply and will be lifeless on awakening.

(4) Hibernate at temperatures that drop below 0*c

Tortoises subjected to temperatures of 0*c or below will literally freeze to death. Even in the best cases the tortoise will end up being blind due to the fluid in the eyes freezing.

(5) Not offer protection against predators

Tortoises hibernated in flimsy cardboard boxes and placed in sheds or outbuildings or when left to hibernate naturally outside were often subjected to rodent attacks.

When  to hibernate.

I hibernate my adult tortoises from December until early April (if April looks like being a cold month I leave them until mid April). I start to wind down my adults in November. I would aim to end hibernation with younger tortoises around March/April so young tortoises need to be kept in their indoor enclosure with full heat and light until you begin your wind down. This is where the fridge method of hibernating is best because you have complete control of when you start and when you finish. I make the decision to hibernate my adult tortoises in August . I weigh them and record if they are a healthy weight (re:Jackson ratio) to hibernate. If they have had no health problems over the year then they are OK to consider hibernation. I do this first check in August because tortoises are at their peak. More checks are needed prior to hibernation if your tortoise is ill do not hibernate. In September and early October you will find that your tortoise is eating less so they can lose a little weight over these months thus making them appear a little light re: Jacksons ratio.

Hibernation Method.

I use and strongly recommend Hibernating your Hermanns tortoise in a domestic fridge. A domestic fridge can keep a steady temperature of around 5*c. It sounds shocking but you will have complete control (with careful planning) over the hibernation conditions therefore allowing your tortoise to have a natural sleep without the risks that mother nature throws at them. The weather in the UK is too unpredictable we can have days in February  where the temperature can rise well above 10*c.  Lots of tortoise keepers are using this method now with great results. The ideal fridge to use is a larder fridge (one without a freezer compartment) The most important thing is to be sure that the fridge temperatures are stable. This can only be assured with careful monitoring. Be aware that a fridge in an outbuilding that is subjected to varying temperatures is likely to reflect those changing temperatures inside the fridge eventually. So protection will be needed to prevent a outbuilding from going to cold. Maybe with a frost guard heater. Once you have decided where to place your fridge it's time to monitor the inside of it where the tortoise will be. This is done using a max/min thermometers with probes. Measure the temperature in different places inside the fridge because it will vary, and you will need to find the ideal spot for your tortoise (5*c). A empty fridge will not be as stable in temperature as a full one and therefore adding lots of mass will help keep the readings stable (see middle photo below. The plastic bottles filled with water). While you are monitoring temperatures it's a good idea to place the hibernation box inside to mimic the time when your tortoise is in there. Once you add things to the fridge, the temperatures will rise and take a while to fall and settle again so the trial run needs to be as near to the real thing as possible. During the trial run, adjust the fridge thermostat (dial with numbers usually going from 1-6, The higher the number, the colder the temperatures) As you adjust the dial, the fridge will take some time to settle and stabilise (as much as 48 hours) and this is why plenty of forward planning is needed. You can use various things to house the tortoise inside the fridge. I use a cardboard box (shoe box) with air holes. You could use something more sturdy such as a wooden box. I have even seen tortoises placed on newspaper directly on the shelves. Tortoises are more comfortable with something to dig/bury into. A sand/soil mixture can be used. I use shredded paper. Newspaper is softer. I then use the max/min thermometer with the probe in the box with the tortoise. You can see in the photo below the thermometers are placed on top of  the fridge so they can be read.

The winding down period

As already mentioned, no food should be left in the stomach of a tortoise when put into hibernation. To make sure that your tortoise's stomach is completely empty a starvation of the tortoise prior to hibernation is essential. The starvation period and hibernation length  will vary depending of the age of your tortoise.

The tortoise is to be given NO food during any stage of the wind down period. It is very important that they are given ample opportunity to drink and are kept fully hydrated. Bath your tortoise every other day which as well as hydrating your tortoise it will also encourage it to empty it's bowels. I do recommend bathing 1 -3 year old tortoises every day. 

The wind down period should be split into 4 stages.

Stage 1 

At the beginning of the wind down tortoises need to have day length and temperatures that are the approximately the same as summertime. This will keep their digestive system working fully and therefore pass any recently eaten food through their system. You may find that your tortoise is slightly slower than they were in the summer.

Stage 2  

You must keep temperatures the same as stage 1 but in lesser quantities. Therefore you should be turning the heat/UV lamps on a little later in the morning and off a little earlier in the evening. This will simulate their shorter day lengths in the wild. Towards the end of stage 2 make the the daylight shorter still making it a gradual process.   

Stage 3    

By stage 3, you will find that your tortoise is coming out from his hiding place less and less. You can now leave the the basking lights off and just have background heat available using a frost guard heater or a tubular heater if in a outbuilding or your central heating if its in your house.

Stage 4

During the beginning of stage 4, any background heating should be turned down to a bare minimum. You will probably find that your tortoise is not coming out at all now and is inactive. Towards the end of this stage, give your tortoise its final bath (not warm enough to stimulate your tortoise) and make sure he is thoroughly dried. Place the tortoise in the box you are using for hibernating. Then place the box in a cool place such as an unheated room or a safe outbuilding which will more closely match the fridge temperature (as long as your tortoise isn't passing anything in his bath water) your tortoise should be ready to go into the fridge. Make sure you weigh and make a note of your tortoises weight before it goes into hibernation.

Your tortoise in hibernation

Once your tortoise is hibernating in the fridge the door of the fridge will need to be open daily for about 1 minute for air exchange. You can alternatively run some piping through the seal in the fridge door. Your tortoise will need careful monitoring during it's hibernation. This will alert you to anything going wrong. Thermometers should be checked at various points of the day and a physical check and weigh will be needed weekly. Within  a couple of days your tortoise should settle down. When making the checks do it at the time of day that is coolest to minimize the risk of disturbing your tortoise. A couple of minutes observing and weighing your tortoise should not disturb it. Check the cloaca area is clean and dry and there are no signs of defecation or urination. If your tortoise urinates during hibernation you will need to get it up because it could easily dehydrate. Some tortoises defecate in the first week or so of hibernation, this is ok just remove the poo. Also check that the nose is dry and clear. Weigh your tortoise and keep a record of how it's weight is changing. A safe guideline is that your tortoise should not lose more than 1% of it's body weight per month. You will find that during the first couple of weeks your tortoise may lose a little weight this is due to your tortoise settling down and being a little active. If your tortoise does lose more than 1% in the first month do not panic. You will find that a few more weeks into hibernation your tortoise will not be losing any weight and therefore it will average out over the total hibernation period.

Waking your tortoise from hibernation.

The wake up time will be at the end of your determined hibernation length or if your tortoise is losing to much weight or urinates. You should bring your tortoise out of hibernation in the morning which will give them the whole day to warm up and hopefully begin drinking and eating. Make sure you have the tortoises enclosure up and running with heat and UV lamps.

Take the tortoise out of the fridge but still in the box and place it in a heated room for a little while. The tortoise will soon begin to stir. As soon as the tortoise has woken up take it out of the box and place it under it's basking lamp. Heat and light are the only things that will stimulate him properly and get his system up and running again. This is very important a  tortoise will not get going and will be lifeless and unable to feed or drink. After your tortoises has been under it's lamp for about an hour or so and is more active give your tortoise a nice long warm bath. Your tortoise will need to flush their kidneys of  the toxins that have built up in hibernation and replenish it's water supply. You may find your tortoise may not do this in it's first bath so give your tortoise lots of baths over the next couple of weeks. Drinking is more important than eating in these first few days. Once your tortoise is active you can offer food. Some tortoises eat within a couple of hours others may take a few days. Continue with warm baths daily.                   

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Copyright © Darran Sproul