Preparing for hibernation
A. C. Highfield
Species that are safe to hibernate are Testudo graeca, Testudo ibera, T. whitei, T. marginata, T. hermanii and T. horsfieldii. The North American Desert tortoise, Gopherus agassizzi has similar requirements.
Species that should not be hibernated include T. kleinmanni (Egypitan tortoise) and Testudo nabeulensis (the Tunisian tortoise) and ALL tropical tortoises including Redfoot tortoises (Geochelone carbonaria), African Spurred tortoises (Geochelone sulcata), Hingeback tortoises (Kinixys species), etc.
Never ever attempt to hibernate a tortoise which you suspect is ill, or which is underweight. To put a sick or underweight tortoise into hibernation is to condemn it to certain death.
In order to survive hibernation in good condition, tortoises need to have built up sufficient reserves of body fat; this in turn stores vitamins and water. Without fat and water tortoises die of starvation or dehydration. Adequate reserves of body fat are vital to tortoises in hibernation; they live off these reserves whilst asleep, and if the reserves run out too soon then the animal's body will begin to use up the fat contained within the muscles and internal organs, eventually these too will become exhausted. Should this occur the tortoise will simply die in hibernation.
The key factors that initiate hibernation behaviour begin in late summer or early autumn. These environmental triggers include:
As these conditions take effect, the tortoise will become less active, and less interested in feeding. We call this the “hibernation induction period”.
This 'fasting' period may last for 3-6 weeks quite safely. We would recommend keeping the tortoises above 55ºF (13ºC) for at least 3 weeks after the last meal to allow time for food in the digestive tract to be processed properly; the most dangerous thing to do is to put a tortoise into hibernation (i.e. below 50ºF (10ºC) immediately after keeping it somewhere warm where it feeds normally. If this occurs, the digestive tract will contain large quantities of semi-digested food and the tortoise is in grave danger. In essence, the food can “rot” internally producing dangerous gasses and toxins.
THE LARGER THE TORTOISE, THE LONGER THE TIME REQUIRED TO DIGEST FOOD IN THE STOMACH
We would not recommend fasting for LESS than 3 weeks even for very small animals.
All of these periods are temperature dependent. At LOW temperatures, the digestive tract slows down, and it will take longer to digest the food in the stomach. At HIGHER temperatures, the process if faster. That is why we rcommend the temperature above, because it is low enough to supress feeding, but high enough to permit continued digestion.
Keeping the tortoise outside (if temperatures are safe) for the first half of the induction period, and then in an unheated room (again, provided temperatures are suitable) for the last half of the "winding down" period is usually very effective.
It will become less and less active, and more and more "sleepy". Eventually, it will not emerge from its sleping quarters very often at all. This is when we consider it ready for hibernation.
Note that while tortoises should not be offered FOOD during this period., they should be offered WATER at least 3 or 4 times per week. Drinking is essential not only to ensure adequate hydration in hibernation, but also to "flush" urates from the bladder.
Tortoises should be checked prior to placing into hibernation and their weight recorded because they lose weight during hibernation. See SAFER HIBERNATION AND YOUR TORTOISE and HOW TO MEASURE TORTOISES for more information on these topics.