I posted this on another forum, thought i'd copy it here for you:

This is a lengthy subject but first you've got to decide if your Mediterranean Tortoise is healthy enough to hibernate.

Has it been eating well on weeds and grasses? Is its nose dry and breathing free from wheezing? Are its eyes clear with no stickiness? Is its poo moist but firm and fibrous and not runny/slimey/very smelly? Is it free from any other external injuries and has it been wormed this year? Is it heavy enough?

The 'heavy enough' always causes confusion. This can be measured using the Jackson ratio, although there is a far more accurate method called the Bone Density Ratio.

The bone density can be calculated by weight in grams divided by the length in cm's cubed (total straight shell length)




This is easier than appears. (Which is good cause i'm rubbish at maths) Firstly turn your tortoise on its back and mark with a pencil at each end of the shell. Accurately measure this length in cm's. Multiply the length by its self 3 times (to the power of 3) then weigh the Tortoise in grams. Divide the weight in grams by the length. Fingers crossed the outcome is between .20 and .25 - if so it's safe to hibernate.

Example of one of my 07 Hermans.
Length 4.8cm, so times that by its self 3 times - 4.8 x 4.8 = 23.04 then 23.04 x 4.8 = 110.592
The weight in grams is 27grams
So 27 divided by 110.592 = 0.24 (just use the first 2 figures after the . ) (and yes i used a calculator)
So the tortoise above has the correct bone density ratio to hibernate. (.20 -.25 as above)

I personally believe all species that can be hibernated should be hibernated and that it has physiological benefits. I'll run on about them in another post.

Which species do and which don’t hibernate?

1. Hermanns Tortoises - Testudo Hermanni. Two subspecies of Hermanns tortoise both are
found across Europe. Hermanns tortoises require a hibernation period, in captivity, of
approximately 10 to 15 weeks.

2. Marginated Tortoises – Testudo marginata. Marginated tortoises are found throughout
Southern Greece and require hibernation in captivity of approximately 10 to 15 weeks.

3. Turkish Spur Thigh Tortoise – Testudo Ibera. This species of spur thighed tortoise is found
across Europe and The Middle East. It is the commonest spur thighed tortoise in captivity and
requires a hibernation period of approximately 10 to 15 weeks.

4. Horsefield Tortoise – Testudo Horsefieldi. Although not really a Mediterranean tortoise
species, they are closely related and are common in captivity. These tortoises are the most
Northerly living tortoise in the world and hibernate for very long periods in the wild. This
species certainly requires a hibernation period in captivity of approximately 10 to 20 weeks.

5. North African Spur Thighed Tortoise – Testudo Greacia. This group of tortoise species live
in a wide variety of habitats across Mediterranean Africa. Larger specimens will generally
require a short hibernation for 6 to 12 weeks. Small specimens should be protected from cooler
temperatures and provided with heat and UV light during winter and hibernation is not
necessary. Specimens with lighter shells come from hotter regions.

6. Klimanns Tortoise – Testudo Kleimanni. This Egyptian species of tortoise is very rare in the
wild and in captivity. They do NOT hibernate.

7. Leopard Tortoise - Geochelone pardalis. A large african species. They do NOT hibernate and should
be kept in hot, dry arid conditions.

8. African spurred tortoise - Geochelone sulcata. Not to be confused with the Spur thighed Tortoises above.
This very large African species does NOT hibernate.

There are also many other popular tropical species that do not hibernate inc' Burmese Browns/Indian Stars/Red or Yellow foots etc.

(Only healthy animals should ever be hibernated. Never hibernate sick or underweight animals)

Hibernation

Hibernation in tortoises is an adaptation used to survive cold winters within their natural range. Since tortoises are ectodermic, they rely on warmth from the sun to maintain their body temperature at around 30oC (88oF). During winter periods, tortoises are no longer able to adequately control their body temperature and normal activity cannot be sustained. Basically hibernation is a dormant period for tortoises, enabling them to sit out the cooler temperatures of winter.

Hibernation is an important biological process and all Mediterranean species of tortoise require some form of winter cooling to remain healthy in captivity. Tortoises which are not hibernated become lethargic. They also grow far too quickly causing them major health problems in later life. Also their natural diet of weeds and grasses is minimal during the winter months. This usually leads to owners feeding 'salad' type foods which are high in phosphates (all supermarket grown food is pumped full of phosphate) and low in calcium and fiber. They also contain other naturally occuring chemicals which are detrimental to a tortoises long term health. It all depends on whether you want to own your tortoise for 10 years or whether you want it to enjoy its natural life span and out live you! Remember, tortoises live their lives slowly and they also die slowly too.

It is important, however, to know more about the particular tortoise species you own. There are several different species of Mediterranean tortoise, and it really depends on their natural range, to determine how long hibernation should be, or whether they should hibernate at all. Please look at the list on the above post. Also make sure you have read and used the post above on Bone Density Ratios (BDR.)


Preparing for Hibernation
To begin with it is important to remember that tortoises do not need a long period of hibernation. A tortoise should never be hibernated for more than 20 weeks. Temperatures during hibernation need to be cool, around 4C, 5C and 6C.

Temperatures tend to be around this during late November and up to late February. So this would be the best time to consider hibernation. Tortoises kept out of doors will begin slowing down in late August as the day lengths begin to shorten. This generally begins with lower appetite levels and shorter activity periods during the day. By the end of September, early October, activity will have almost completely stopped during the day, to just a few hours sunbathing (weather permitting).

Tortoises which live indoors in heated conditions rarely show signs of hibernation at all, generally only beginning with intervention from the animals owner. Preparation should really begin around 3 to 4 weeks before and really begins with fasting. Tortoises must not enter hibernation with food in their gut, since its digestion grinds to a halt, food would decompose, and kill the hibernating tortoise.

They have a very slow metabolism and to fully empty a tortoise gut of food may take up to 4 weeks for a large animal, 2 – 3 weeks for smaller and juvenile tortoises. During this fast period it is important to give tortoises access to a bit of heat during the day. Approximately 4 – 5 hours of access to a heat lamp should suffice. This access to heat allows the tortoises gut to remain functioning in order to clear out its contents.

Hydration is also very important and during the fasting time tortoises should be bathed daily in shallow lukewarm water. An old washing up bowl or new cat litter tray is ideal. Fill the tray up to the tortoise’s gular scutes and leave the tortoise to soak for 10 – 15 minutes. Bathing tortoises is the best way to get them to drink, and tortoises often urinate and defecate when placed in water, essentially clearing the animal out and re-hydrating them.

After 3 to 4 weeks the tortoise should no longer be producing faeces and urine should be clear. The tortoise is now ready for hibernation. At this stage, cool the animal to room temperature to make it sleepy.

The Hibernation Period

There are 3 main ways to artificially hibernate a tortoise.

1. The Box Method
This is basically a great improvement on the original method of hibernating tortoises in captivity.
The best type of box to use is a large polystyrene fish transport box, easily obtained from most good aquatic retailers. These boxes are well designed for insulation and are ideal for the job. The tortoise should be placed in a small cardboard or wooden box just a little bigger than the animal. Place a small amount of shredded paper in the box with the tortoise for bedding. This box can then be placed inside the polystyrene box. Suspend it in the centre of the box, surrounded in shredded paper. Pack this paper well around the box forgood insulation. The centre of the poly box is the most insulated place for the tortoise to be and keeping it there is very important.

This method has the least control of external temperature and being well insulated from extremes of temperatures is very important. A digital thermometer with probe can be used to monitor hibernation temperatures throughout. Place the probe of the thermometer in the inner box with the tortoise, placing the digital read out on the outside of the poly box. The entire
box setup can then be placed in an outhouse, garage, shed or cool spare room.

Temperatures during hibernation must stay at around 5C mark, at this temperature tortoises will only loose approximately 1% of their body mass per month. Lower temperatures and the tortoise will freeze to death. Higher temperatures will burn its reserves to quickly and may even wake the animal up. Wherever the box is placed it must be protected from damp and must be protected from rats and mice, which may eat the tortoises. During the 10 – 15 week period check temperatures daily.

2. The Fridge Method
This is my favourite method. In this method a fridge is used to control temperatures accurately during hibernation. I place a digital high/low thermometer in the frige for a couple of weeks prior to hibernation to check the fridge is performing well.

Although a good method it is not without risk. Only ever use new fridges, old ones are less reliable and may accidentally freeze your tortoise to death. Ventilation is very important inside the fridge. So cut a small hole in the top and bottom of the door seal to allow some air movement or as I do make sure the door is opened a few times a day. The tortoise itself can be placed in a cardboard box just slightly larger than the tortoise, with a small amount of shredded paper for bedding. The box can then be placed in the fridge set at 5C. Keep a digital thermometer on the fridge reading the internal temperature permanently and check temperature daily for the 10 – 15 week period. I have never lost a tortoise using this method and have hibernated tortoises as young as 8 weeks old as long as they meet the BDR as mentioned in an earlier post (above.)

3. The Natural Method
This method is probably the best method for the tortoise and yet the most controversial captive method of hibernation.
In the wild tortoises bury themselves in dry sandy soil usually under shrubs. Buried beneath the surface they are fully protected from the harsh weather above ground. It would not be wise to allow tortoises to burrow anywhere they like in the garden, since it would be hard to protect where the tortoise would dig making it difficult to tell whether the animal would be safe during hibernation. Tortoises must be protected from waterlogged soil or predators like rats. If this method is to be used then it should only be allowed to take place within the confines of a greenhouse, with a soil base.

Dig over the floor well before and add plenty of sand to loosen it. The greenhouse will protect the tortoise from extremes of weather. Once the tortoise has been properly fasted, they can be allowed to dig down below the surface. Once they have dug in, a layer of straw or dry fallen leaves can be placed across the floor of the house, for extra insulation. Make sure
predators cannot get into the greenhouse and check all entrance points regularly throughout hibernation. Make doulbly sure the greenhouse has NO leaks or your tortoise could drown during hibernation

Tortoises can only be allowed to hibernate in this way if they are extremely healthy since it is much more difficult to check them through hibernation.


Hope the above helps put some minds at rest.

Hi, my Horsefield is approx 1 1/2 yr old, we got at the begginning of the summer and has become a true member of the family. She was very active and inquisitive until approx 5 weeks ago she stopped feeding and burrowed in its home. I immediatelly thought she is trying to hibernate however advice from two reptile places advised me not too allow her to do so. I've monitered the tempeature and it does not drop below 20 degrees at night and 32 degrees during the day. They advised me to keep a night lite bulb on through the night and get a heat matt. the temp now is more constant now approx 28 degrees however the tortoise just sleeps all day and we just here a little scratching now and again. I believe the tortoise was fit and well before it started to sleep, shiney black eyes, clean nostrils and very active in the garden. I am concerned do I hibernate her or not. Obviously it is my first tortoise and I want to do whats right for her. Any advice would be appreciated.

I'd say that your tortoise is doing what nature intended it to do and hibernate. Chances are it may be a wild caught import as very few are captive bred at the moment. If so it's already preprogrammed to hibernate. Horsefields hibernate for 6 to 9 months in the wild!
I personally don't keep horsefields, perhaps someone who does will comment further.

__________________
"If we could walk with the animals, talk with the animals,
Grunt and squeak and squawk with the animals,
And they could squeak and squawk and speak and talk to meeeeeee"
Bobby Darin.