Hibernation in Testudo sp.

The following guidelines and information is for many of the Mediterranean species of tortoise. This may include most of the Testudo sp. with exceptions like Furculachelys naebulensis previously Testudo naebulensis and Agrionemys horsfieldi, previously Testudo horsfieldi. Specific hibernation criteria and advice should be followed for a given species. Please ask one of our recommended reptile veterinary surgeons for species advice and prehibernation checks.

Preparation and the cooling period

Hibernation is recommended in those species that would naturally hibernate in the wild, therefore correct species identification is important and clearly the first step. Hibernation or cooloing temperature range is 3.8-15ºC depending on species and geographical distribution. Reptiles found in moderate mountain climates would generally be within the lower end of the range, whereas those found in subtropical climates often will need access to a heat source. Tropical species do not hibernate but they will encounter lower night temperatures, rarely below 21ºC. These species are preferably kept at daytime temperatures similar to summer1.

Tropical species kept and bred in captivity do not require a temperature decrease as this could result in serious immunity issues such as respiratory disease amongst others. Photo period is an important consideration which will be discussed in the lighting section. Most reptiles kept and bred in captivity in the United Kingdoim are prepared for hibernation around the autumn equinox 2.

Clinical examination prior to hibernation is highly recommended to assess the tortoises health status. This may include a physical exam, a faecal parasite test and a blood test. Diagnostic imaging (radiology or ultrasonography) may be advised in some cases.

Once the tortoise is considered healthy for hibernation a fasting period of 3-4 weeks is started in order to empty the gastrointestinal tract to prevent fermentation of contents. 

Daily baths are advised which may last 15-30min for hydration purposes to assure that the bladder is full as this will act as a water reserve. Tortoises are able to reabsorb water from the bladder when required.

Tortoises maintained indoors normally would be maintained at room temperatures by switching off the heat source and decreasing the photo period gradually. Room temperatures can be checked, ideally selecting a room that is cooler especially if central heating is used.

In countries where a tortoise is maintained outside would normally start to slow down once environmental temperatures fall below 15ºC which coincides with a decreasing photo period. The number of hours spent outside are increased during a 3 week period to allow for a gradual decrease2

Hibernation accommodation

The use of fridges are the safest way to hibernate your tortoise assuming air is changed regularly and temperatures are stable and regularly monitored. A different fridge to that used for food for human consumption is recommended due to the potential zoonotic risk2. Temperature should be around 5ºC (2-9ºC)and humidity guaranteed. Exposure to sub-zero temperatures must never occur and maximum daytime and minimum nighttime temperatures should be monitored closely as fluctuations may occur.  Many exotic animal and tortoise referral hospitals use this system and have done so for many years with minimal problems.

Hibernation outside in the UK is not recommended due to the following risk factors: flooding, frost damage, trauma from rodents, inability to monitor closely. Each year tortoises are presented to us with frost damage which may include blindness, loss of the sense of smell and food recognition, neurological signs including circling. If hibernated outside they are unlikely to awaken until March-April which makes hibernation time too long.

Regular weight checks are important and they should never loose more than 8-10% bodyweight during hibernation. If weight loss is detected this may be due to fluid loss due to low humidity, urination or temperatures being too high, a common sign for the latter is increased activity which may only be a head raising and observing when the fridge is opened. If a tortoise is woken up they should not be returned to hibernation 2.

Prolonged hibernation which in some cases may reach 6 months, leaves insufficient recovery and grazing time to prepare for the next hibernation period. These tortoises are debilitated and physiologically challenged by such husbandry. One must also remember that most of the Mediterranean species are resistant species and many will survive year after year but many more will perish. The natural habitats of Mediterranean species will encounter long periods of high temperatures followed by short periods of cooler temperatures, whereas by challenging them with the opposite is not natural and many will become very ill or die. Post-hibernation problems are common and may include anorexia, stomatitis, and kidney disease - these are the pathologies that we most frequently encounter every year and often these animals require critical care hospitalisation with placement of feeding tubes and medications.

The recommended maximum length of hibernation if 3 months for a healthy adult tortoise and these would usually be put in to the fridge around November after a cool-down period before awakening in January or February. Alternatively they may be kept at higher temperatures until we decide to "create" their winter around January or February time - therefore hibernation would run untill April/May. This is often a good idea because once they awaken we can make the most of sunny days and allow them to forage for weeds like dandelions.

What age should they be hibernated?

Avoiding hibernation entirely is unnatural and often causes problems like accelerated growth and early maturity. When we look in to the natural behavior of many of the Mediterranean species in their natural environment - if we consider a young Spur-thighed Tortoise in the South of Spain, these will be hiding away from predators under low shrubs, often with slightly higher relative humidity in these microhabitats and consume a diet with very high fiber content in an overall dry environment. This often differs to the husbandry in captivity. If they are not hibernated and fed daily on a mixed diet it is obvious to see that we are changing their natural foraging behavior and habitat. Young tortoises that are over-wintered tend to have increased natural growth rates and sizes when compared to those hibernated in captivity or the wild specimens; carapaces tend to be smoother too. We would therefore encourage controlled husbandry changes during the entire "cooling" period (pre-hibernation and hibernation periods), which includes food restrictions with adequate decreased temperatures and even a short hibernation in a fridge for 1-3 weeks.

There are different opinions regarding the starting age for hibernation as there is some degree of risk involved, although very low if key-points are followed. Some european specialists in zoological medicine would say start hibernation in year 1, although it seems that more are of the opinion to start in years 3-4.

The key point is not to encourage optimal temperatures and diet all year round as this will cause increased growth rates often coupled with ill health.

Waking up period

Considering the maximum hibernation time of 3 months in healthy adult specimens, once this time has been reached they should be woken up slowly so that their metabolism and organ function starts to increase steadily. Tortoises should be checked for obvious problems which include swellings, mouthrot (stomatitis) or nasal discharge.

Healthy animals that are awakening from hibernation should be bathed twice daily to enable drink.ing and voiding of urine and possibly faeces.

Temperatures should be slowly increased - these can be increased in two stages: first maintained in a tortoise table between 22-25ºC with natural and ultraviolet light. Temperature during this period is important due to the fact that we could be dealing with an immunesuppressed animal, especially if hibernation was longer than it should have been. A basking spot ie a mercury vapour lamp can be connected where basking temperatures may exceed 30ºC. 

Different foods like melon or cucumber may be offered to start with and gradually switch to their normal diet. A healthy tortoise that has just come out of hibernation should certainly eat within the first week - See post-hibernation anorexiaThose tortoises that do have post-hibernation anorexia due to negative energy inbalances often require the placement of an oesophagostomy tube to enable daily feeding. Thses can stay in place for long periods of time and normally these tortoises will start eating with the tube still placed.

Tortoises following hibernation often will have lower white blood counts (immunity cells) making them more vulnerable to infections. Urea may also be elevated due to the acumulation of toxins during hibernation. Often a blood sample collection is necessary to check organ function and haematology so that we can act promptly as time may be limited 2.

Species commonly kept in captivity:

  Testudo graeca

  Testudo hermanni

  Testudo marginata

  Agrionemys horsfieldi
-No feeding 3-4 weeks
-Hibernate in a box within a box
-High humidity and good ventilation.
-Consider shorter hibernation period
-5ºC (2-9ºC)
-Temperature should never drop below 0ºC
-Monitor high and low temperatures
  Furculachelys naebulensis
-Should not hibernate (Highfield 1996)
  Trachemys sp.
-Although considered hardy species, should not be hibernated in captivity
  Terrapene carolina triunguis
-Can hibernate 2-3 months
-Prepare in cooler room as per Testudo sp. but with leaves, soil and moss to maintain humidity.
-Dependant on climate may be kept outdoors (Not UK)
-7-16ºC (Boyer 1992b)
-Should never drop below 0ºC
-Check max and min temps
  Terrapene ornata
-As per T.carolina triunguis
-Those more southern species do not hibernate
-As per Terrapene carolina triunguis
  Kinixys belliana
-Temperature drops in winter may stimulate sexual behaviour
-(Chin 1996) reduce photoperiod from 13 to 11 hours per day and reduce temperature from 23-32ºC to 18-20ºC  for 8-10 weeks. No feeding and no basking during this time.
  Geochelone carbonaria

  Geochelone pardalis

  Geochelone sulcata

  Geochelone denticulata

  Cuora amboinensis
-Do not hibernate
  Gopherus agassizii
-Similar to Testudo sp.
-Similar to Testudo sp.


1.- Mader Dr (2006) General Husbandry and Management. In: Reptile Medicine and Surgery, ed. Dr Mader, pp. 29-30. WB Saunders Philadelphia.

Mader D (2006) Reptile Medicine and Surgery, WB Saunders, Philadelphia.

2.- McArthur SD, Wilkinson RJ and Meyer J (2004) Medicine and Surgery of Tortoises and Turtles. Blackwell Publishing, Oxford.

3.- Girling SJ and Raiti P (2004) BSAVA Manual of Reptiles Second Edition. BSAVA, Gloucester.