As the nights draw in and the temperature drops, many of us begin to think of hunkering down. Thick jumpers, warm fires and comfort food. For some animals, this change in season will bring about similar thoughts. For them, it means the start of a period known as hibernation. Most people, when talking about hibernation, will think of animals such as hedgehogs and dormice. But some animals that are kept as pets will also have to hibernate and it’s vital to allow them to do so safely. 

What is hibernation?

Hibernation isn’t just curling up and going to sleep. It’s an incredible process during which the animal slows down their rate of metabolism to as little as 5% of normal, lowering their heart rate, breathing rate and body temperature. During the winter, there is less food around. So this state of extreme inactivity allows them to conserve enough energy to survive through until Spring. 

In other countries, larger mammals such as bears and chipmunks will also hibernate. But in the UK only three mammals will do so – hedgehogs, dormice and bats. 

What about squirrels?

We often think of other animals such as squirrels, rabbits and badgers hibernating, but they don’t; instead, they can enter a state known as ‘torpor’ which is somewhere between a deep sleep and hibernation. Torpor is like a short-term hibernation and the animal can wake and re-enter the state regularly, even daily. Whereas with hibernation, even though the animal is able to rouse, especially if the temperature drops to dangerous levels or there is a need to eat or toilet, it occurs much less frequently.  

Does my pet have to hibernate?

Obviously, pets such as cats and dogs don’t need to hibernate. But some more exotic species do need an extra long lie-in as winter descends. However, only one of the more common pets truly needs to hibernate – the tortoise. Other animals that are sometimes kept as pets, like snakes and turtles, may enter a period known as ‘brumation’. This is similar to torpor but occurs in cold-blooded animals. However, this is fairly unlikely as it will only occur if the temperature in their environment drops low enough; which is uncommon in modern homes.

Small mammals like hamsters can also enter hibernation if they get too cold but this can be harmful. So it’s crucial to keep them warm and cosy. Interestingly, although wild European hedgehogs will hibernate, it is dangerous for pygmy hedgehogs kept as pets to do so, as they are too small and don’t carry enough body fat to survive long periods without food. 

How to hibernate a tortoise

The Mediterranean tortoises such as the Spur-Thighed, Hermann’s, Horsfield’s and Marginated will all require hibernation and there are certain steps that must be followed. 

It is vital that before a period of hibernation, the tortoise is as fit and healthy as possible and has a good store of fat reserves

An ill or underweight tortoise should never be hibernated as there is a high chance of death. Owners should start to think about preparing for hibernation as the end of summer approaches. They can do this by weighing and measuring the tortoise and carrying out a basic health check. This could also be done by a vet if you are unsure. 

If the tortoise gets the all clear, then the hibernation induction period can begin. 

The shorter day lengths and colder temperatures of late summer and early autumn mean the tortoise will begin to slow down and lose interest in feeding. These environmental conditions should be replicated if the animal is kept indoors. 

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Once they have had their last meal before hibernation, the tortoise will need to undergo a period of fasting 

This is to allow time for the food to be digested. Though they should still be offered water baths to prevent dehydration. Depending on the size of the tortoise, this fasting period can be between 2 and 4 weeks during which they will gradually become less and less active and when they get to the point at which they don’t emerge from their sleeping quarters, they are safe to be hibernated. 

And yes, the rumours are true, the current advice for the safest place to hibernate a tortoise is in the fridge! 

But obviously there are guidelines for how to do so safely as temperature control is vitally important. Too cold and the tortoise could freeze to death; too warm and they’ll wake up prematurely. 

Hibernation will last from around 2 months for smaller tortoises to 4 months for larger species. 

As the tortoise comes out of hibernation, they will require heat, light, food and water. Post-hibernation anorexia can commonly occur, so if the tortoise hasn’t eaten within a week of waking up, it’s important to get them checked by a vet with knowledge of reptiles. 

A cryogenic frog?

Though highly unlikely to be a pet, there is one species that deserves a special mention when talking about hibernation – the Wood Frog. This little creature lives mainly in the forests of Alaska and takes the idea of hibernation to a whole new level. When the temperature drops below freezing, the frog also freezes – they stop breathing, their heart stops beating and their blood freezes. They are essentially dead. But because they are able to fill their cells with glucose instead of water, this doesn’t freeze and instead preserves the frog in a state of suspended animation until such a point as the temperature increases and the frog returns to normal. 

Although it can sound tempting to curl up and go to sleep for weeks at a time, hibernation is a complex process that, in the wild, requires plenty of preparation, and for hibernating pets, requires plenty of owner knowledge. As always, if in any doubt, speak to your vet for more information.  

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