Many species of tortoise that are kept as pets in the UK would hibernate throughout the winter in their natural habitat. Hibernation involves reducing the metabolic rate and temperature of the body, so that it has a reduced energy requirement and can survive periods of time when resources such as food are hard to find.
The reptile community is currently divided in their opinion on whether pet tortoises should be hibernated or not. One group has the viewpoint that hibernation is natural and, as tortoises do tend to slow down in the winter months anyway, we should let them hibernate just as their wild relatives do. Other people have the opinion that there is no need for a tortoise to put its body through the level of stress that it endures during hibernation, because in captivity we can provide light, warmth, water and a constant supply of food during the colder months.
In this article, we will help guide you on whether your tortoise is suitable for hibernating and, if you decide to hibernate them, advise on how to make the process as safe as possible.
Which species hibernate?
Not all species of tortoise hibernate so it’s important you firstly work out what species of tortoise you have and whether or not they should be hibernated. If you are unsure what species of tortoise you have, please speak to an experienced vet or a tortoise specialist.
Mediterranean species of tortoises DO hibernate and this includes:
Spur-Thigh (Testudo graeca)
Hermann’s (Testudo hermanni)
Horsfield (Testudo horsfieldi)
Marginated (Testudo marginata)
Leopard tortoises (Stigmochelys pardalis) and Sulcata tortoises (Geochelone sulcata) are examples of species that DO NOT hibernate.
As some species are spread over large natural ranges, some members of that species will hibernate where as others, at the warmer end of their natural range, will not hibernate.
Is my tortoise a good candidate for hibernation?
If you have only adopted your tortoise this year, it is not advisable to hibernate it.
Any tortoise that has been unwell during the year should also not be hibernated. Tortoises need a good fat reserve and should be as fit as possible if they are to survive a hibernation period.
Hatchlings (tortoises that have hatched during the current year), should not be hibernated as they will not have enough reserves to survive a hibernation.
The Jackson ratio graph can be used with the Hermann’s tortoise (Testudo hermanni) and the Mediterranean Spur Thigh tortoise (Testudo graeca), to help guide us on whether the tortoise is of a suitable weight to size ratio for hibernation. This involves comparing the length of the plastron (the bottom half of the tortoise shell) with the weight of the tortoise.
Only hibernate tortoises that you know are fit, healthy, free from underlying health problems and are in a good body condition.
How can I prepare my tortoise for hibernation?
Ideally your tortoise should have a pre-hibernation check up with a vet to make sure it is well enough to be hibernated. The check-up may just involve a clinical exam, but other recommended tests include a faecal sample to check for internal parasites.
It is very important that tortoises undergo a pre-hibernation preparation period to ensure they are ready for hibernation. The 2 main aims of this period are to ensure the tortoise is well hydrated and to make sure the gut is emptied completely, as any food left inside the tortoise will rot during hibernation.
Large tortoises (over 2kg in weight) will need a month of fasting whereas small tortoises (less than 1kg) can be fasted for 2 weeks before they are hibernated. During this period, the ambient temperatures should be gradually dropped until they reach between 10 to 15 oC. The tortoises should also be bathed at least a few times per week to allow the tortoise to become well hydrated and also to encourage defecation to empty the gut.
How do I hibernate my tortoise?
There are three main methods that people use to hibernate their tortoises:
Underground: Some people allow their tortoises to hibernate themselves in the garden or in a greenhouse, whereby the tortoise digs a hole and buries itself underground. The big issue with this method of hibernation is that it is exceedingly difficult to monitor the tortoise during hibernation. They can also suffer damage from freezing temperatures, and it leaves them susceptible to damage from rodents and other predators.
In a box: Tortoises can be hibernated in an insulated box which people will often leave in a shed or garage. With box hibernation is can be difficult to regulate the temperatures in the box. This means temperatures can often drop below freezing in the middle of winter which can lead to permanent frost damage such as blindness. Rodents can also easily chew through boxes and bite the tortoise causing severe and life-threatening damage to the tortoise’s legs and shell.
Fridge hibernation: this method of hibernation has become popular with many tortoise keepers as it allows the tortoises to be monitored closely in a safe and protected environment. Fridges are usually between 4 and 8 oC, which is the perfect temperature for hibernation. Drinks chillers often are the best fridges to use, and it is advisable to put the tortoise into a lidded separate container (with air holes) within the fridge to prevent contact with any cooling surfaces. The fridge should be opened every couple of days to refresh the air.
How do I monitor my tortoise during hibernation?
It is advisable to check your hibernating tortoise every 7 days as a minimum. It is important to weigh your tortoise during hibernation and if your tortoise has lost more than 5% if its body weight you should wake your tortoise up from hibernation.
If your tortoise urinates during hibernation, you should also wake them up as this means they have lost a large part of their water store and will risk becoming dehydrated.
How long should I hibernate my tortoise?
Hibernation should be limited to a maximum of 3 months for adults and yearlings can be hibernated for up to 6 weeks. Hatchlings should not be hibernated.
How do I wake my tortoise up from hibernation?
After removing your tortoise from its hibernation box, it is important to start bathing the tortoise at least once a day to allow it to drink and urinate. Drinking and correcting dehydration is more important than feeding initially.
The tortoise should be placed into a warm environment and a heat lamp should be provided to allow for basking temperatures of above 30oC. Food can be offered after the first bath has been given and most tortoises will start eating on the day they are woken from hibernation.
Tortoises should have urinated and started to eat within a week of coming out of hibernation and if your tortoise has not done this, it is important to seek veterinary advice as soon as possible.
Remember that the experienced vets at Vet on the Net can assist you with any questions or concerns you may have about hibernating your tortoise. We can also arrange for faecal samples to be submitted to a specialist laboratory as part of the recommended pre-hibernation check-up and help to guide you on treatments that may be required.
Dr Louise Abuzet BVM&S CertAVP(ECC) CertAVP (ZooMed) BSc(HONS) MRCVS
RCVS Advanced Practitioner in Emergency and Critical Care
17th of December 2020