Sussex Chelonian Society hope in this page to answer some of the questions most commonly asked about hibernation Mediterranean Tortoises - please feel free to seek further advice if you are not happy with it. Address at the end of the page.
Hibernation is the state in which certain anmials (some mammals, reptiles and ampibians) pass the winter in a dormant state with their metabolism greatly slowed down. In other words they slow down to the point where they stop all activity but are still living. "Hiberna" is the Latin for winter. There is a condition that is almost the opposite - like in an excessively hot summer - where animals, including tortoises - bury themselves and shut down their systems to conserve energy to survive - this is known as "aestivation" after "Aestivus" meaning summer.
Certain animals are totally independant on external conditions to maintain optimum health. Reptiles have no internal heating mechanism like mammals do - they are cold blooded therefore rely no getting their energy from the sun. If the sun is overhead most of the that's fine! - but the earth is tilted and in winter then Northern Hemisphere gets a shorter length and colder temperaturesat night.
Tortoises are not natural inhabitants of the Britsh Isles - most of the pet trade imported tortoises from the Mediterranean which is much further South than we are - therefore their normal winter day length and temperature drop is different. It follows that if we choose to keep tortoises in this country they will have to undergo a longer period of inactivity than they would in the wild. We owe it to them to do it properly and make sure they are fit to undergo this long period. It has to be said with the "greehouse effect" our weather seems to be changing and our winters are not as reliable as they used to be in terms of length or severity.
It, therefore, means that you have to take your cues from their behaviour and not just do what you always did (hibernate them on the same date in late October and expect them to emerge on the same date in early March). Tortoises do a lot better by hibernating than by being kept up during the winter - the adrenaline boost they get on waking up gets them going more than if they had been kept awake for several months. It is certainly good for hatchlings whose shells develop more smoothly.
The triggers for hibernation are a combination of the light intensity, daylight length and temperature dropping. In the wild tortoises seem to hibernate from between two to twelve weeks depending on where they are. It had been normal for tortoises in this country to hibernate for five months - slightly less in the South, more in the North. Indian summers in the autumn and early mild springs of late mean that althought the light intensity and daylight length has been dropping as expected in the autumn, the temperature has not necessarily done so. Recent Febuarys have been very warm.
You will notice that as autumn approaches, your tortoise starts getting up later in the morning, and goes to ned earlier in the afternoon. During the summer, mine usually are stirring by 7.30am, bask for an hour to absorb then eat and hide out of the sun till lunchtime, they nibble and hide again, but are active around 4.30-5.30pm before finding their preferred place to sleep overnight. Obviously on grey days they do not bother so much, but their behaviour definately starts to change as winter approaches. Go with the flow unless your animal is underweight or sick. Keep an eye but do not worry if it does not eat so much - it is totally normal! Your animal is programed to hibernate on an empty stomach so it will stop eating about four weeks before it thinks it is ready. There will come a point when you realise that your tortoise is almost dormant, and that is the time to prepare for hibernation.
Your tortoise might choose to hibernate itself by burying itself in the garden. After all, this is perfectly natural and is what happens in the wild. You will either know where it is - or you will not !! Several members tortoises do this year after year without ill effects, and some of mine do it this sometimes before I have had a chance to round them all up. If you are concerned, you can always mark the place and cover it with extra insulating material (straw or old carpet) Keep an eye in case predators try to dig it up, but this is not a common problem. Watch out for muddy pairs of eyes staring at you in the spring.
If you plan your tortoises hibernation you need to find a cold place that is frost free. You should also make sure that predators cannot get at the box. The ideal temperature is 4°C and is certainly not more than 8°C or 9°C - otherwise the tortoise is merely dosing and continuing to draw on its reserves, not hibernating. A brick built shed, outhouse or garage is ideal. Wooden sheds can let in the frost. Indoors could be fatal as it is usually too warm. It might be worth trying your loft if it is well insulated from the rising heat from below - test it with a thermometer for a few days first. Some people use an old fridge as the salad drawer at the bottom is usually the temperature you require.
Indoor hibernation is best achieved by having two boxes for each tortoise, one bigger than the other. The smaller box should be larger than the animal with a bit of room for it to settle in. Line this box with shredded paper, newspaper torn into strips or polystryrene packing chips. Do not use hay, straw or leaves as these carry fungal spores which can produce respitory or eye problems. Punch some air holes into the sides and top; place your tortoise in the box and cover it with more packing material. Put the lid on and prepare to put this box inside the bigger box (prefrably of wood), which you should also line with similar packing material. The end result should be a tortoise with cavity wall insulation!! The outer box should also have small ventilation holes, and you can add to the protection by placing an old rug or blanket over it. It is a good idea to stand the box on peices of wood to raise it slightly off the ground and allow air to circulate. You should hibernate hatchlings in exacly the same way - I hibernate that year's hatchlings (1" long) for six weeks and anything bigger than that I treat as adults.
Tortoises must be fit before hibernation - weigh and measure it using the Jackson ration (add link). Your animal should be wormed every other summer using Systemex (from your vet) as the worms remain in the gut thus depleting the tortoise even further. You can keep an eye on your tortoise during hibernation by weighing it - the loss is normally about 1% of body weight per month - anything more than 5% in a month is serious and you should wake your tortoise immediately. Tortoises that do not settle and become restless ven though it is cold, should also be brought back indoors and kept up with bright lights and warmth. To keep them up you are going to have to counteract their natural tendendancy to hibernate by having bright lights over them for 16 hours a day and heat to get them active enough to eat.
Tortoises dehydrate during hibernation and their bodily fluids thicken. It is vital that you soack your animal in warm water and allow it to drink. Check it all over carefully and bathe each eye seperately making sure they have not been frost damaged or have infections. Ensure that the mouth opens freely and watch keenly to see there is evidence that it's bladder and bowels are working!! (This sometimes takes a few days) It is not uncommon for female tortoises to jettison over-wintered eggs at this time - I have never known these to hatch. It usually takes up to 3-5 days for the tortoise to start eating - if it doesn't, try turning up the temperature.. Dandelion leaves are still the best food to offer but try a variety of foods if it is still reluctant to eat. Put them outside if the sun shines and bring them in at night until the normal temperature overnight is over 10°C. Put both sexes together straight away as the spring is the time for mating! The females have just had a few months thinking thank goodness for the rest - the males have been dreaming about it and can't believe it was really true!