HIBERNATION Natalia Rodrìguez Ana Reboledo Curso Inglés Veterinaria

It is important to limit, monitor, shorten, or even in some situations avoid hibernation. A short and safe hibernation may be completed without problems, but a well planned “overwintering” where the animal does not hibernate may decrease the number of diseases that are a direct result of hibernation. Tortoises alter their natural behaviour at the end of the summer in response to falling diurnal temperatures and decreasing daylength. Tortoises stop eating and became less active. It is at this time that a well-managed tortoise should be in optimum condition with ample body fat reserves to face hibernation period. Hibernating mediterranean tortoises in northern latitudes will be exposed to metabolic stress beyond those they would naturally encounter in the wild. Do not assume these animals are able to look after themselves without careful management.

Complications include ear abscessation due to infection ascending the eustachian tube from necrotic food in the bucal cavity. Tortoise should be encouraged to drink prior to hibernation. Some authors suggest that the tortoise may well use the fluid stored within its bladder as its fluid reservoir Tortoise that are ill/debilitated, under treatment for a specific illness or are underweight with inadequate fat reserves should not be hibernated Getting ready to Hibernate Reptiles are ectothermos so they face a real challenge living in temperate climates in winter.

Injection site abscesses, irritation and overdose are possible complications. It is far more important for the veterinary surgeon to perform a full clinical examination in order to help the client decide whether or not hibernate the tortoise. It has long been somewhat of a tradition for clients to bring their tortoise to veterinary surgeons for a pre-hibernation vitamin injection. Such animals are likely to die during hibernation or awake significantly worse than when they commenced their hibernation.

SUMMARY CONSIDERATIONS BEFORE hibernatION

check the tortoise’s health early in the autumn (before the equinox) check the tortoise’s weight routinely but especially at the start of hibernation. Ensure the tortoise has no eaten within four weeks of hibernation. Confirm that the tortoise has been provided with the opportunity to drink before hibernation. Ensure hibernation facilities offer protection from extreme temperature changes, are well-ventilated, are away from car fumes, are checked regularly though out the hibernation for suitable temperature ranges and are secure from dangers such as rodent attack.

Ideal conditions during hibernation Temperature Hibernation is significantly temperature dependent The optimal maintenance temperature throughout hibernation is about 5 °C. Temperatures below 2°C are potentially dangerous, and at temperatures above about 11°C tortoises tend to become active.

Apparently some UK tortoise owners are now using carefully monitored fridges for hibernation. A daily check ensures an air change and temperatures can be accurately maintained.

Duration of hibernation Weather Latitude Fat reserves Species Size and age Health status

The autumn equinox is considered to be the time at wich animals commit themselves to hibernation. If a tortoise requires over- wintering then it is best to provide artificial heat and light from this time onwards so that the metabolism does not wind down towards hibernation status. A hibernation period should not exceed 20 weeks. A more natural latitude it may be as short as 4-6 weeks .

OVERWINTERING TORTOISES Tortoises can be overwintered, this is the prevention of hibernation by provision of a suitable environment for the tortoise to remain awake throughout the Winter. The optimal temperature range of overwintered Mediterranean tortoises is 18-25ºC during daytime, falling to 14-16ºC during the night. Many over wintered tortoises suffer from dry eyes and skin if inadequate levels of humidity are provided. Most tortoises require very bright illumination in order to stimulate feeding. “Tru-lite” tubes are desirable as they may allow continued activation of vitamin D3. Food should not be situated directly under heat sources (to prevent drying).

POST-HIBERNATION PHYSIOLOGICAL CHANGES The low metabolic rate during hibernation and the maintenance of a prolonged period of inactivity results in many physiological changes upon awakening.

A tortoise that has recently hibernated will have Low fat reserves A low white blood cell count A poor level of hydration Accumulated high levels of metabolic toxins (e.g. urea/urates) An increased level of protein catabolism to provide energy A low blood glucose level and little glycogen reserves Low levels of vitamins, especially those fat soluble

The following conditions can often be observed in the post-hibernation period Eye, nerve and brain damage as a result of exposure to excessively low temperatures Mouth infections (necrotic stomatitis) Upper respiratory infections ( runny nose syndrome) Shell damage from rodent attack Chronic debility (e.g. vitamin A deficiency) Jaundice Post-hibernation anorexia (PHA)

A POST-HIBERNATION CLINICAL EXAMINATION Compare weight measurements to pre-hibernation values. Compare weight measurements to species averages. Use regular weight measurements to assess progress throughout the season.

Blood urea levels are their highest in the immediate post-hibernation period. Blood urea levels approaching 200 mmol/litre are consistently fatal in the post-hibernation period. The implication was that urate levels are also high and precipitation of urate within the renal tubules resulted in kidney failure as did the nephrotoxic effect of metabolites.

NUTRITION Most healthy animals eat within one week of emergence from hibernation. Blood glucose levels have a significant effect on appetite. A peak blood glucose level is produced in healthy animals within the first few days of rising. Failure to eat within a reasonable time of rising from hibernation is termed post-hibernation anorexia (PHA).

GloSsary Overwintering: Invernaciòn Awake: Despertar Shell: caparazón Jaundice: Ictericia

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