What happens to wildlife over the winter?
What happens to wildlife over winter?
The colder weather has finally made an appearance, and wildlife at our natural burial grounds will be ready for winter. Some animals like the pink-footed geese that visit Cothiemuir Hill join us as they migrate to the UK. Other species like the swallow migrate away from the colder weather to places like South Africa.
You will find animals that are active throughout the winter months like our rabbits and deer. We often see these out and about in the winter woodland at Delliefure. There are also those that prepare to overwinter, sleep or slow down during the darker days and declining temperatures. This includes mammals that live in the woodland at Hundy Mundy and Henley On Thames. It includes Amphibians that we cannot see sleeping on the bottom of the pond at Aylesbury, Pembrokeshire and Bath. There are Reptiles like slow worms and grass snakes who like to shelter in wood piles. Then there are the really little creatures like insects that also need to overwinter. These find shelter in foliage like the blankets of Ivy found in our wooded areas at Dorset, Usk and Cardiff
A place to shelter and sleep
When winter arrives the changing cold weather triggers processes like hibernation, brumation, torpor, diapause and dormancy. These are all ways animals have adapted to see out colder months, or months when they need to conserve energy. But they are slightly different processes and they affect different animals and wildlife. It’s also good to know where you may find wildlife sleeping because we don’t want to wake them up too early.
Sometimes in the spring we get a spell of warm weather like an unseasonably warm weekend and decide to have an early spring clean. If temperatures do not remain above 10 degrees on a regular basis after our spring clean it can harm the animals we have disturbed. If we remove their shelter too early and the frost and winter weather creep back in they are no longer able to shelter from the cold. So this is something to consider when tidying the garden. It’s important to know about the sleeping habits of our wildlife and how we can support them if we want them to survive. There are things we can do even in the spring and summer months which will create shelter for wildlife in the winter.
What is hibernation, brumation, torpor and diapause?
But what is the difference between hibernation, brumation, torpor and diapause? Which animals use them and how can we support our wildlife better over the winter? These are some of the questions we are going to explore. If we understand how these amazing creatures live and survive it gives us the ability to work with nature. For us, it means we can ensure the animals living at our natural burial grounds are left to sleep safely. Sometimes it’s as simple as waiting a few weeks to allow the warm weather to stabilise.
What is Hibernation?
Some of our mammals like Deer, Rabbits, Moles and Grey Squirrels stay active over the winter months. They may change their feeding patterns slightly. We find that rabbits become less active and stay closer to the burrow but are out and about. However, a few of our mammals (warm-blooded animals) go into hibernation. Hibernation is a state of extreme inactivity when an animal’s metabolism slows down lowering its temperature, heart rate and breathing so they are barely active. By doing this they preserve their energy so they don’t have to forage for food in the winter months. They can stay tucked away throughout the whole of winter inactive, however, they have to find a safe, warm space to do this. There are only 3 species of our native animals that enter what is considered ‘true hibernation’. These are our hedgehogs, dormice and native bats.
Hedgehogs are one of the animals that we sometimes find foraging for food at our natural burial grounds. In the winter they will retreat to our wooded or sheltered areas where they can build a safe nest to hibernate. These are often in areas like leaves, log piles or undergrowth. At Pembrokeshire Natural Burial Ground you will find a hedgehog box made from recycled materials in Jesse’s bug hotel too. If you bring your dogs to a natural burial ground just be wary if they start to disturb areas like these. They may have found a hedgehog in hibernation.
You can find hedgehogs tucked away in log piles, compost heaps or piles of leafy cuttings at home. Finding a space for these is one of the ways you can help animals like hedgehogs. The fungi that you may find on dead wood in log piles are also a great winter food source for waking wildlife. You may have a permanent space you can place log piles and cuttings, but you can also allocate an area you leave vegetation until spring. It’s also why it’s really important to compost or recycle dead wood and vegetation rather than burning it. Not only does this lock away carbon stored in dead wood, reducing carbon released and allowing nutrients to return to the earth. It also means sleeping animals can be gently relocated to a safe space.
Hedgehogs will hibernate through the winter until about March or April. Occasionally they may wake up for a quick snack if the weather warms, but they will go back to sleep until warmer weather has permanently arrived.
Bats are one of the animals we are lucky to see flying around Cothiemuir Hill Natural Burial Ground. During the winter they go into hibernation and a state called torpor. Torpor is where they lower their body temperature and metabolism to see through cold periods of weather. If there is a cold spell they can enter a torpid state for a few hours or a few days to save energy. In the winter they are barely active so this becomes a true form of hibernation. In the UK they are usually out and about until November. However this year (2022), we had very mild December weather so you may have seen them later in the year.
When the weather starts to cool they will disappear, usually for 4 or 5 months and head to their roost. This is somewhere dark and cool with a constant temperature where they are safe from predators. It’s why caves are the perfect natural environment. You will find them in barns, abandoned buildings, and even old mine shafts. A large number of bats also hibernate in trees so this is something to consider when felling and cutting trees. Especially if there is a hole or space where a bat can crawl in and curl up.
Bats usually reappear around April when the weather gets warmer. They may wake on warmer late winter and early spring evenings and enter a torpid state when the weather cools again. But we really start to see them again in spring. This is when temperatures have risen and their food source (moths and insects) are active. If you want to find out more about their yearly cycle there is a great page with ‘a year in the life of a bat’ from the bat conservation trust.
The Dormouse is one animal that you may find in the deciduous woodland at Usk Castle Chase Natural Burial Meadow. They love places with hedgerows and woodland trees that produce nuts and berries. Dormice are quite difficult to spot as they only come out at night and are very small. They spend a lot of time hibernating or in some form of sleep.
In the winter they find somewhere to hibernate. This can be for half a year or more. During hibernation they will curl up in a log or in a pile of leaves tucked away at the base of a tree. They tend to wake from this form of hibernation around May.
Dormice can also go into a torpid state to conserve energy. This is something they may do over the warmer months if they find food is scarce or temperatures drop. When they are active in the warm summer months they will sleep during the day and venture out at night. All in all, they love to curl up and sleep.
What is Torpor?
We may think of warm-blooded mammals like badgers going into hibernation but they actually go into a slightly different state called torpor. We have mentioned torpor above as some animals hibernate and can go into a torpid state. But torpor is different to hibernation. The animal will lower its metabolism to go into a state of reduced activity where its metabolism, heart rate, temperature and breathing lowers, but it does not go into a full state of hibernation. It’s a short-term form of hibernation where it will wake after a few hours or a day. Torpor is also a state an animal goes into to conserve energy which may be due to a cold snap or when food sources are low rather than a seasonal change. This means it’s something an animal may do in warmer months when circumstances dictate it.
Badgers like the ones we have at some of our natural burial grounds will enter a torpid state during very cold periods. They reduce their activity over the winter to help conserve energy. Part of this means staying in the sett more, which is why we see them less. They will go into periods of torpor. This helps to conserve much more energy than ‘normal sleep’ which allows them to prolong their fat reserves.
Other animals also follow this pattern too. This includes some squirrels and birds. In fact, hummingbirds use torpor as a way to store fuel before their migration so they use torpor for slightly different reasons.
We may not see animals over the winter months because they are less active, but they are not always in full hibernation. However, it’s important that during the winter months, we respect the spaces they choose to retreat to. This is part of what helps them survive. You can see one of our beautiful badgers caught on the wildlife camera at Pembrokeshire Natural Burials in this video. This badger was very active in the summer, but with the recent cold weather, it should be snuggled safely in its sett.
What is Brumation?
Brumation is the state of inactivity that reptiles and amphibians go into over the winter months. It’s their form of hibernation and has some similarities. Like hibernation animals going into brumation will find shelter. Their metabolism slows, temperature drops and their ability to conserve energy increases. Yet this state is different to hibernation as animals will wake on warmer days to go in search of water and food. Only cold-blooded animals brumate and it is something that is triggered by shorter days and lower temperatures. Brumation can last for long periods, it depends if rising temperatures wake an animal. Those that wake can then re-enter brumation when temperatures lower again.
Where do reptiles go over winter?
Some of the reptiles that you may find brumating in the woodland at our natural burial grounds are the grass snake, slow worm and common lizard. Often they are so well hidden you won’t see them, even when they are active.
In the cold weather, reptiles find safe spaces to brumate. This includes underneath trees roots, rocks, log piles and fallen trees. Some snakes will also use an empty rabbit warren. You may find them brumating in the compost heap and under log piles or vegetation in your garden. This is why these places are so important as they help to support areas where native habitats, with tree roots or fallen trees, no longer exist.
Where do amphibians go over winter?
As temperatures drop and we head into the colder months, amphibians like frogs, toads and newts start to disappear. This is because, like reptiles, they go into brumation. At our natural burial grounds in Aylesbury, Bath and Pembrokeshire you may find some amphibians brumating in mud or leaf litter on the bottom of the pond. This is a risky strategy because if a pond freezes over it can lead to a lack of oxygen. This may be why many amphibians including choose to ‘hibernate’ on land. In native habitats, they will dig into loose soil or under rocks. You may also find them at home in compost heaps and grow bags. Anywhere that stays warm and will not freeze in the cold weather. As with reptiles, lowering temperatures dictate when amphibians start their brumation. If temperatures warm they may wake up but will re-enter brumation when temperatures lower again.
Frogs are really amazing because not only can they brumate, but they also have the ability to survive part of their body freezing. If you come across a frozen frog don’t immediately think it is dead. This is because their liver creates its own form of internal antifreeze. A high level of glucose stops their internal organs from freezing. As long as the frog keeps a certain percentage of its body in an antifreeze state the rest of its body can thaw. This allows frogs to survive freezing conditions.
What is diapause?
Diapause is when an arthropod (this includes our insects), suspends development because of environmental conditions. This can happen at any time during the insect’s life cycle and any time throughout the year. Cold weather is one of the conditions that can trigger diapause. This can be for survival reasons or to align with seasons like reproductive cycles.
Moths & Butterflies (Lepidoptera)
The different ways that butterflies and moths can survive our winter conditions are amazing. They have adapted to do this in a few different ways. Some, like the painted butterfly, will migrate. Others like the peacock butterfly go into a state of diapause. Some adults do not survive the winter and rely on their overwintering caterpillars and pupa to continue the next generation. These will find areas to lie low like leaf litter or soil where they burrow into slightly warmer areas. Here caterpillars or pupa will enter diapause until warmer weather arrives.
Sometimes you may find a butterfly that has decided to find a space to see out the winter in your home. But our heating can bring them out of diapause too early as they rely on temperatures to tell them when it’s safe to emerge. If this happens the best thing you can do is place them in a slightly cooler place where they won’t be disturbed so they can re-enter this state. Somewhere they can find a place to crawl into and sleep until they are naturally woken.
Over the winter we no longer see our beloved bees. They have found some amazing ways to adapt to the cold weather and these can differ between species.
Honey bees huddle up in the hive for warmth using movement as a way to retain heat in the hive. When it comes to bumblebees only the queen will survive the winter. The rest of the colony dies, but the queen will enter a state of diapause. After building up her fat reserves with nectar she will find somewhere safe under the soil to remain through the winter months. You may even find these in your plant pots. If you do, gently recover the queen until she is woken by warmer weather. After winter she will recolonise with eggs she has laid.
Solitary bees leave the overwintering to the next generation laying eggs that will grow into mature bees, but these will wait out the winter in their cocoon also in a state of diapause. In the spring they emerge and start this process again.
The best way to help our bees over winter is to leave them be. Don’t spring clean the garden too early, and grow early spring flowering plants for those that may be woken early by a warm weather window. The more nectar they can get when they emerge, the better their chance of survival.
We don’t see beetles over the winter like our ladybirds. This is because, like some of our other insects, they enter a state of diapause to survive the cold weather. They will find somewhere safe, whether this is under rocks, in a log pile or in a soil bank and dig into the soil where it is warmer. Here they will suspend their development until warmer weather returns.
This is why you may find insects like beetles in leaf piles, your veggie patch or compost heap. It’s why it’s important we don’t spring clean too early. If they do not have native habitats nearby like our woodland at Hundy Mundy Woodland Burial Ground and Henley On Thames Woodland Burial Ground they still need somewhere to survive the cold weather. They are a really important part of our ecosystem. Ladybirds are also one of our natural pest controllers, so supporting these insects means we are protecting the flowers and vegetables in our gardens in a natural way.
What is Dormancy?
While it may not apply to animals, there is another process we see in the winter where plants and trees go into a state of dormancy. These are living organisms that feel the cold and while some trees are able to survive the winter as evergreens, deciduous trees and plants go dormant. During the dormant season, trees stop growing and lose their leave. This returns nutrients to the ground and also provides much-needed leaf litter and dead wood for the animals that we have discussed above so they have an important role to play in winter processes.
These trees may still be developing their root system below ground, but above ground they are inactive. When more suitable environmental conditions arrive their sap starts to rise through the tree to give new life to their branches.