Jacqui's Captive Bred Tortoises

 

Introduction.

 

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:

• A fall in ambient temperatures – the days are cooler and the top temperature is reducing, day on day.
• The length of the day becomes shorter (The pineal gland monitors this, in the tortoise)
• The daylight intensity reduces. The sun is in a lower position and any sunlight the tortoise feels during the day is less intense. (This is also monitored by the pineal gland)

 

Natural hibernation.

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.

 

Controlled hibernation.

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 the

UK . 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:

• The temperature must remain above 2 degrees Celsius and below 10 degrees Celsius. A temperature of 5 degrees Celsius is considered optimum, hence the use of a fridge! This temperature needs to be stable throughout the whole of the hibernation.
• Tortoises must NOT be hibernated whilst their stomachs contain undigested food, hence the fasting period before entering hibernation (see guidance below.). The fasting period varies according to the age and size of the tortoise, because this impacts on its metabolic rate. Very young tortoises would only need about 14-20 days where as larger ones and adults need 4-5 weeks, to ensure their gut is completely empty. Guidance from the tortoise trust site or a reputable reptile vet is recommended for setting the fasting period.
• A sick or underweight tortoise must NEVER be hibernated. Again consult with a reputable reptile vet or use the Jackson ratio measurement (for Hermans - prior to wind down) or the McIntyre ratio (for Horsfields - prior to wind down) which can be found on the tortoise trust site, this is a mathematical formula to ascertain correct weight to length. (I can email these to you if you request them via my contact form)
• Tortoises should be checked frequently in hibernation, this will not harm them, they are responsive and this should be monitored. Any tortoise that has urinated MUST be got up and kept up immediately. This is where the fridge method is useful as it allows for weighing, checking and monitoring throughout the whole hibernation. It is advisable to place the tortoise in a box, plastic clear boxes are ideal as they can be observed without too much intrusion, placing the tortoise on clean white paper towel, hand towel or using white shredded paper as packing material around the tortoise to stabilise the temperature, is also beneficial in order to ascertain if the tortoise has urinated. However, if using a fridge, reliable temperature monitors must be used and ventilation is also necessary. Many keepers buy a fridge just for this purpose as you can then remove the door seal, for ventilation and run an oxygen pump (similar to those that blow bubbles in fish bowls) in order that fresh air can be pumped in and stale air pumped out through a space in the bottom of the door. Daily opening the fridge door, for a second or two will also replace the stale air.
• When using the fridge method, any empty spaces in the fridge should be filled with medium in order to stabilise the temperature. I have used plastic bottles filled with water and found this works really well.
• The sides of the fridge should have cardboard taped to them so the tortoise can not go right against the cold walls and risk any frost damage.
• The fridge must be a “larder type” and not have a freezer box/compartment as frost damage can lead to blindness, brain damage and death. If using the household fridge for one or two tortoises, the salad drawer is ideal. However, for larger collections a separate fridge is recommended due to disturbances of going in and out of the household fridge and the light going on and off! The fridge needs to have been on for several weeks at 4c-6c (5c is optimum) before placing the tortoises inside.
• Water should be added to a small container, separate from the tortoises to add a little humidity as fridges are very dry. Make sure a tortoise cannot fall into the water and drown.
• Weigh the tortoise just before putting in the fridge and record the weight. The tortoise should not lose more than 1% per month and no more than 10% throughout the whole process. They can lose more at the beginning and then settle down to negligible loss from weeks 2 onwards. EG a tortoise that weighs 300g on the day it goes into the fridge, should lose no more than 3g a month and no more than 30g over all. If the tortoise appears to be losing weight rapidly or has reached the 10% level then awakening and over wintering is advised.
• Check the temperature several times a day to monitor any fluctuations. Digital or laser thermometers are the best as the probe can be placed in the bow with the tortoise and the digital reading can be easily accessed. Laser thermometers are very expensive but I have found them invaluable as you can “zapp” the tortoise (taking care to avoid eyes with laser) and see exactly what temperature it is in an instant. Alarms on temperature monitors are also useful in case of a power failure or the fridge not working properly.

• Weekly checks are then needed to ensure the tortoise has not urinated and to weigh it. This does not disturb the tortoise and it will quickly resume its passive state. However, it is vital to ensure the tortoise is alive and not dehydrating due to urination.
• If temperatures in fridge rise for what ever reason to above 10c and your tortoise will wake. You will then need to get it up and keep it up. Never return a tortoise that has been awake to hibernation. However, it is worth noting that they will move, respond and even open their eyes whilst checking them. I have also had some hibernate with their mouths slightly open, this is not uncommon and nothing to worry about.

• If using a more natural method, the substrate needs to be at least 1 metre deep and the box lined with insulated board/rot proof material, filled with topsoil and play sand. Tree bark mulch can be placed over as a top layer to retain some humidity. A frost heater must be in position in the tortoise house if natural hibernation is to be allowed. This method does prevent regular inspection of the tortoise, so is perhaps for the more experienced keeper? It has a good safety record and is used by many experienced keepers.
• If it is necessary to “over winter” or keep awake a tortoise due to fragility or illness, then it must be maintained indoors with heat and UV light being maintained daily throughout the winter. Feeding can also continue in this situation but some more commercially prepared foods such as Florette Crispy salad mix may need to be used as weeds become scarce. The other alternative is to grow weeds indoors over the winter for food.

 

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.

 

Juvenile Tortoises.

 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.

 

Adult Tortoises

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 end of Hibernation

At the end of hibernation or when the period is up, move your tortoise in its box to a warm room in the house. When it awakes fully normal basking temperatures of 30+ need to be available with a background temperature of 20c. Bathing is important after they have warmed up a little to hydrate the tortoises again.

Bath daily for a week, initially then every 2-3 days for an adult, daily for a younger tortoise, until they are urinating, eating and drinking.

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!