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The following guidance is what I have written based on sound information collected by reptile specialist vets, tortoise experts, those who have collected research evidence (such as the Tortoise Trust) and my own experiences as a keeper for many years. It is a guide to introduce the idea and allow new keepers to understand the process better. I am aware that the Tortoise Trust has produced a DVD called “safer hibernation” and would recommend new keepers obtain a copy of this for clear guidance, to support my written descriptions.
Tortoises that hibernate are those coming from climates where there is changeable seasonal weather and associated variable temperatures. Herman’s (T. hermanni) and Horsfield (T.horsfieldi) tortoises are both hibernating species.
Hibernation is the part of tortoise husbandry that most new keepers dread. However, if a few simple guidelines are followed then it need not be such an anxious time.
Many people have kept tortoises in the past, as children, and are now adults but they remember that their tortoise died in hibernation. This was quite common with non controlled hibernation. However, in the UK where the weather conditions are not predictable and winter temperatures can vary considerably on a daily basis, controlled hibernation is the only way to ensure your tortoise survives. There are not many keepers now who have “free range” garden tortoises that they just leave to their own devices over winter. Most keepers exert some kind of control over hibernation, whether that is the housing used, frost free heaters, the wind down technique or the monitoring during hibernation.
To hibernate or not?
The prevention of hibernation in a hibernating species is a subject of much debate amongst tortoise’s keepers and groups. There is an argument that they do not need to hibernate in the UK if maintained indoors over the winter. However, the tortoise trust has completed research in this area and noted an increased level of liver disease and decline in fertility in long term over wintered tortoises. Their conclusion being that only sick, fragile and very underweight tortoises should be over wintered.
There is also discussion about at what age tortoises should start hibernating from. Personally, I do not hibernate any of my babies until they are 3 years old. This is my own view and I realise in the wild tortoises would normally hibernate from hatch, in order to survive extreme temperatures, lack of available food and avoid predators. However, tiny tortoises are fragile (susceptible to fluctuations in temperature and de hydration because of their small body mass) and I am not aware, at this time, of any longitudinal studies collecting data of how many tiny babies hibernate in their first 3 years and how many re emerge safely in the spring. I feel that new keepers need to be more experienced with tortoises and understand the process very clearly before attempting to hibernate their babies, and for this reason I personally recommend over wintering for the first 3 years and would base this on the assumption that the keeper can gather confidence, knowledge and experience during this period to begin hibernation at year 3.It has been noted that the growth of juveniles that are hibernated is slower ensuring a smoother shell growth closer to that of natural growth in the wild. This added to the health and fertility benefits, leads me to recommend hibernation year on year from the age of 3 as long as the tortoise is not very underweight or sick.
Why do tortoises hibernate?
Hibernation, in tortoises is a response to the falling of temperatures. Tortoises regulate their body temperature by how they interact with their environment, they are ecotherms.
With the onset of winter, temperatures drop so low that tortoises can no longer regulate their own body temperature in this way, so their response to it is to enter a state of inactivity or dormancy.
The triggers for hibernation for your tortoise are:
In the wild, the tortoise body starts a natural process to get ready for this dormant state. This is natural, automatic and very difficult/almost impossible to stop. (I have even had sick tortoises start this process when in reality they would not be able to survive a natural hibernation.) The tortoise body begins to convert excess food into fats and sugars and store it. The liver stores up glycogen (made from blood sugars) and the organs store fat.
From mid September onwards, keepers notice that the tortoises’ behaviour starts to change. It will spend longer basking and progressively less time eating. By late October/early November it will have stopped eating all together in preparation for hibernation. The tortoise will however continue to defecate and urinate in order to eliminate as much waste products from the system as possible. Once this process is complete, and the environmental factors have told the tortoise it is time, it will dig into the ground or select a shelter (sometimes these are vacated rodent burrows). The tortoise often uses the same hibernation site each year. Once underground, the tortoise continues to monitor the surrounding temperatures and adjusts the depth that it rests at accordingly, digging in deeper if the frost line deepens and back towards the surface as it feels temperatures increasing.
During hibernation the tortoise’s movements are sluggish but it is not “asleep” and is still responsive. Their metabolism slows to vital operations only and it requires minimal oxygen to survive, so breathing slows right down to an almost negligible level too. The kidneys continue to function, producing small amounts of urine that is then stored by the bladder. As a result of this, toxins begin to build up in the bladder through lack of elimination from the body. The tortoise gradually dehydrates, as urea builds up and it continues to excrete tiny moisture droplets as it breathes.
As spring draws near and temperatures rise to above 10 degrees Celsius. The tortoise feels the increase and begins to wake. Initially, this may bring the tortoise up to bask, digging in again at night, but soon the tortoise will resume its normal behaviour patterns.
Inside the tortoise the liver releases a massive dose of glucose which provides a surge of energy in order for the tortoise to eliminate the high level of toxic waste it is carrying, by urinating and it will begin to drink and feed.
It is important to understand the natural process so that this can be applied to a controlled environment due to the inconsistent weather/temperatures in theUK . Tortoises making good use of the garden will normally begin true hibernation in November. With this in mind food should be withheld from mid October allowing for the tortoise to follow a natural pattern of emptying the gut and excreting waste products whilst storing fat and glycogen.
Suitable hibernaculum’s in the UK are a fridge, where the temperature can be controlled and is stable, or an outside building/tortoise house that has a frost heater and deep enough substrate to allow a natural process but whilst ensuring the tortoise is not subjected to frost. It also allows for the controlling of access to food.
Many tortoises kept as pets in the 70’s etc died in hibernation because they were put in their box, in the garage, shed, loft etc to hibernate and it was either too warm meaning they just died of starvation as they did not enter hibernation or they were poisoned through the fermenting of food in their gut producing toxins and causing death.
During a controlled hibernation the following points are critical:
Example of hibernation wind down programme. (Based on a schedule written by Brian from www.simplytortoise.co.uk)
Please note: this is produced only as a guide and the advice of a reptile vet is recommended.
These can be hibernated safely for 6-8 weeks after following a wind down of about 20 days.
Days 1-5 - No food, 12 hours basking at 32c, background temperature 20c, tepid soak in shallow water daily.
Days 2-10 - No food, 8 hours basking at 32c, background temperature 20c, tepid soak in shallow water daily.
Days 10-15 - No food, no basking, background temperature 20c, tepid soak in shallow water daily.
Days 15-20 - No food, no basking, background temperature between 20c reducing to 10c. Tepid soak in shallow water daily.
Can be safely hibernated for 10-12 weeks but after a wind down of 28 days.
Days 1-7 - No food,12 hours basking at 32c, background temperature 20c, tepid soak. daily.
Days 7-14 - No food, 8 hours basking at 32c, background temperature 20c, tepid soak daily.
Days 14-21 - No food, no basking, background temperature 20c,. tepid soak daily.
Days 21-28 - No food, no basking, background temperature between 20c reducing to 10c, tepid soak daily.
The urates (white stuff) may look a funny colour (creamish, whitish grey is normal) or be gritty when they first pass it after hibernation, this is also normal. Some tortoises do not eat the same day they wake up, but all should be eating within a week. If not then I recommend a visit to the reptile vet to ensure the tortoise does not have any underlying condition requiring treatment.
Your tortoise will now resume its normal activity and be in better health as a result of the winter slumber!