This is a response to environmental constraints caused by the changing seasons.
In their natural environment, the activity of tortoises is determined by the temperature of the air and water: in this case, we refer to ectothermic animals (often incorrectly referred to as cold-blooded animals).
In reality, solar energy, as well as photoperiod, will be crucial in regards to the movement of animals, both in their natural environment and in captivity: thus, tortoises will move from place to place depending upon whether they require heat or cold.
This behaviour allows them to regulate their body temperature.
However, when the ambient temperature becomes unstable (too high or too low), the animal will go into a slowed state of existence, thereby reducing all its normal activities (food, digestion, movement, mating, etc.).
In the case of low temperatures, we refer to lethargy or hibernation.
In the case of high temperatures, we refer to asaestivation (dormancy).
For aquatic tortoises:
Hibernation may take place outside, for example in a pool of water, or inside, in an unheated room, in a container with water or a damp surface. For hibernating underwater, aquatic tortoises inhale water through the cloaca and the end portion of their intestinal system operates as a gill. Thanks to this process, tortoises can retrieve oxygen, which will allow them to spend an entire winter on the bottom of a lake!
How do you hibernate your tortoise?
If your tortoise lives in ideal conditions, such as outside in a garden, it will place itself into hibernation as soon as the temperature and brightness decrease. However, you must always make sure that your tortoise has access to a shelter (piece of cork, wooden housing) in which you can add more dry leaves or straw in order to protect it from the cold.
If you do not want to risk your tortoise hibernating outside, you can hibernate it in controlled conditions, such as in a cellar or garage, with a temperature of between 4 and 10 degrees. Place your tortoise in a box full of earth and straw, and ensure that the room remains dark during the entire duration of hibernation.
Some people do not hibernate their tortoises for fear of losing them. This is strongly discouraged because hibernation is part of the life cycle of tortoises, and it is particularly this period of winter hibernation which triggers ovulation in the females of the species. Also, be aware that a tortoise that does not hibernate will grow faster than a tortoise that hibernates.
For land tortoises:
Land tortoises also need the heat of the sun. During intense heatwaves or during the winter season, when the heat of the sun is no longer suitable, the tortoises may enter into a state of lethargy, during which their body temperature, heart rate, and breathing decreases. When climatic conditions reach a critical point for their survival, tortoises begin to burrow underground and attempt to completely bury themselves. For example, under some climate conditions, hibernation is induced by a decrease in the daytime temperature and a decrease in the number of daylight hours.
Note: The temperature of the environment in which the animal is exposed during this period of dormancy must be between 4 and 10 degrees.
In nature, the length of hibernation depends on the climate and the latitude. For animals bred in captivity, it is also necessary for the size, age and general state of health to be taken into account.