One of the best known facts about hedgehogs is that they hibernate. But when does hibernation happen, why do hedgehogs hibernate and are they actually asleep?
Hedgehogs are one of only a handful of mammals that are true hibernators, and their hibernation usually takes place in the UK from late November until mid-March or early April. The length of a hedgehog’s hibernation can vary dependent on climate and temperature.
When a hedgehog hibernates is dependent on weather conditions, when the temperature drops, and if the temperature remains low. When this happens the hedgehog will retreat back to their nests, which can be underneath hedgerows, piles of logs, within old rabbit burrows, under sheds or in a human made hedgehog house. Rather than hibernating continuously throughout winter, they tend to wake up fairly frequently. However, it is unlikely they will leave their nest. This waking up could be caused by external noise or disturbance, or unexpectedly hot weather. If it gets really cold, they will build a new nest rather than add insulation to an existing one.
Are hedgehogs asleep when they hibernate?
Hedgehogs, or mammals in general, being asleep during hibernation is a misconception. Rather than being asleep, they enter a state know as ‘Torpor’. This means they become immobile with their bodies cooling down from 35c to just 10c, and brain activities slow along with their breathing. A hedgehog’s heart rate will decrease from around 190 beats per minute to just 20 per minute when they are hibernating. This makes any activity impossible
Doing this saves a lot of energy during a time when food sources are scarce. In warmer climates, such as New Zealand, hedgehogs don’t always have to hibernate due to food being available year round. Hibernating is a great way to preserve energy and survive cold winters, it not without risk however.
Is hibernation dangerous?
The act of hibernation itself isn’t dangerous, however it does come with inherent risks. The biggest being that the hedgehog is immobile and vulnerable to predators whilst hibernating. This is why they require a protective nest to rest in whilst winter blows through. The cold weather however can bring further dangers, with the main one being that the air temperature falls too low. If their nest isn’t warm enough, and the outside temperature is below freezing, then ice crystals can form in a hedgehogs blood. When the temperature drops like this, their body functions will become active again, and wake the hedgehog up to help keep itself warm, and to find a warmer spot.
What to feed hedgehogs before hibernation
Before settling down to hibernate, hedgehogs need to build up a reserve of bodily fat. They are fairly happy eating most things, including insects, slugs, mice, fruit and more. This means that the average garden should provide them with most things they need. If you have a garden or outdoor space, you can help complement this diet by putting out cat or dog food, or hedgehog specific wet and dry foods. If you use cat or dog food, make sure it doesn’t contain fish. Also, do not put out milk as hedgehogs are lactose intolerant and so this will make them ill. Providing a bowl of water will most certainly be welcomed however.
As mentioned in a previous blog, don’t feed mealworms to hedgehogs as this can cause health issues.
Alongside food, you can also help hedgehog build nests by providing suitable habitats and homes for them to reside in. You can also keep a part of your garden with dense undergrowth and piles of leaves which hedgehogs will be able to use for nest materials.
When do hedgehogs leave hibernation?
Hedgehogs leave hibernation in spring, once the weather has warmed up. This tends to be from mid-March into April. Hedgehogs that have just emerged from hibernation can be easily identified as they look underweight, and you may see them in lighter hours. During this time, putting food out for hedgehogs will be hugely beneficial to them as they look to recover from the months of hibernation they have just endured. Males tend to emerge first, with females joining them 2 weeks to a month later.
Typically, a hedgehog will lose around 25% of body weight throughout hibernation. So on waking, they will need to eat and drink quite urgently. If the weather then changes once they have woken, this can have a detrimental effect, and is why spring time is one of the business for hedgehog sanctuary’s.
Humans can help during this by providing water and food in hedgehog safe feeding stations and keeping an eye on their garden visitors. Most hedgehogs will be a little wobbly a few days after coming out from hibernation, but this should pass after a few days. If they continue to look a little worse for wear, then they may be unwell and require help. Hedgehogs out in the daylight, asleep on your lawn or looking drunk can be a sign of trouble, and you should phone your local hedgehog rescue ASAP.