Pre- and post-hibernation problems in Mediterranean tortoises

Abstract

Mediterranean tortoises have suffered significant health problems in captivity in the UK for many decades, largely through widespread misinformation and ignorance about their husbandry and nutritional needs. Certainly, the widely accepted practice of keeping them outdoors year-round in what is a totally unsuitable climate contributes massively. The pre- and post-hibernation periods are times of high morbidity and mortality in tortoises. It is important for veterinary professionals not only to recognise how to prevent such problems by advising on appropriate care, but also to treat such issues successfully in the clinic environment. The following article discusses the major failures in captive care that contribute to peri-hibernation problems in tortoises, as well as outlining their diagnosis and treatment.

Guide to hibernating Mediterranean and Horsfield's tortoises

“…Tortoises should also be weighed in grams on accurate digital scales on day one of hibernation, and then weekly for the whole duration of hibernation. If the tortoise loses over 5 per cent of its starting bodyweight then it is recommended to bring the tortoise out of hibernation (McCormack 2016). On average, a healthy adult tortoise will lose 1 per cent of its prehibernation weight each month; for example, a 1000 g tortoise can safely lose 10 g a month during hibernation.…”

Risk factors influencing brumation success in captive tortoises in the United Kingdom

“…13 It is generally accepted that in a captive environment, juveniles should be allowed a short period of brumation 3 and this has been suggested to be carried out in preference to overwintering, to control growth rates. 11 Brumation preparation did affect outcome and a statistically significant association was found between a controlled pre-brumation temperature reduction and survival. In the wild, tortoises will be exposed to a slow decline of temperature, shorter day length and a decrease in food availability which is associated with a decrease in metabolism and activity which prepares the animal for brumation.…”

“…Evidence base for the age at which tortoises should be brumated is lacking; however, in the wild, hatchlings and juveniles will undergo brumation from their first year as ambient temperatures decrease 13 . It is generally accepted that in a captive environment, juveniles should be allowed a short period of brumation 3 and this has been suggested to be carried out in preference to overwintering, to control growth rates 11 …”

“…Using an insulated box method has similar problems, as tortoises may be exposed to temperatures below freezing, leading to tissue damage, or to temperatures which are too high, leading to the tortoise rousing and utilising reserves. 11 In recent years, the use of a fridge or a chiller has become a recommended brumation method due to the ability to closely control temperature and monitor the tortoise. 3 The aim of this study was to evaluate brumation methods being used for pet tortoises in the United Kingdom and to identify potential risk factors for mortality and post-brumation morbidity.…”

“…In the UK climate, this can lead to excessively long brumation periods, with a risk of flooding, freezing or predator attack. Using an insulated box method has similar problems, as tortoises may be exposed to temperatures below freezing, leading to tissue damage, or to temperatures which are too high, leading to the tortoise rousing and utilising reserves 11 . In recent years, the use of a fridge or a chiller has become a recommended brumation method due to the ability to closely control temperature and monitor the tortoise 3 …”