Precious Slumber

As the nights draw in and temperatures drop, many of us long to sleep through winter and only wake up when spring arrives. Local wildlife expert Wendy Carter of Worcestershire Wildlife Trust offers a guide to some of the creatures who do just that.

Winter can be harsh for our wildlife – freezing temperatures, piercing winds and snow on the ground make it difficult to locate food. Seeds will have dispersed. Berries, ripe and juicy in autumn, will have been gobbled up or rendered inedible by frost. Many insects will have buried themselves in the ground or lie beyond reach in crevices, often as eggs or pupae. It all adds up to a situation in which finding the nutrients essential for survival becomes a real challenge.


There’s also another basic problem. Keeping warm in low temperatures takes a huge amount of energy, burning calories fast, especially for creatures with a large surface area and short, thin fur. Whilst a few small animals like shrews adopt extreme strategies such as shrinking their internal organs (and even their brains) in order to make it through the season, others have no choice but to hibernate.


So what is hibernation?

A handful of UK animals including hedgehogs, dormice and bats – even frogs, lizards, snakes, newts and bumblebees – hibernate. It’s a complex physiological state that makes normal activity impossible. Creatures might look like they are sleeping but hibernation is much more than this - a truly deep slumber in which they are able to conserve energy by lowering body temperature and reducing breathing, metabolic and heart rates. Oxygen consumption is reduced and blood flow to main organs restricted.


The process is triggered by the shortening of the days and hormonal changes and it can last for days, weeks or even several months. Its primary purpose is simple: to use less energy and facilitate survival for many weeks without food.



Depending on the weather and their general health, hedgehogs hibernate from October/November until March/April. They must feed intensively and get into peak condition before hibernating if they are to have enough reserves to last the winter. The gardener’s best friend, they’ll hoover up slugs at an amazing rate so are well worth encouraging onto your patch.


One way you can do this is to provide suitable nesting sites including log piles and wild areas or even a purpose-built hedgehog home. Fallen leaves and prunings make ideal nesting material so make sure you don’t clear all of them away. Hedgehogs particularly love apple and cherry leaves whilst sticks of hawthorn and honeysuckle make good structural supports.


Even for healthy individuals, hibernation is no small feat. A hedgehog’s heart rate, when awake, can be anywhere between 200 and 280 beats per minute but during hibernation it drops to just five beats per minute. If the ambient temperature rises or drops, the hedgehog’s body will automatically lift or lower its metabolic rate to compensate – much more energy efficient than being awake and struggling to source food in hostile conditions.


Research has shown that hedgehogs change nesting sites at least once during hibernation so they can sometimes be seen out and about during winter. However, it’s unusual to see a hedgehog staggering about in the colder months or during daylight so if you do see one and it looks unwell, it might need a helping hand.


If you come across an underweight hedgehog, the first step is to provide supplementary food and fresh water. Hedgehogs will relish any combination of meatbased wet dog or cat food, specialist hedgehog food or cat biscuits. Place it in a shallow dish and put in a sheltered area of your garden around sunset. The British Hedgehog Preservation Society can offer further advice and help you find a rescue centre near you if needed. Please visit



With their long honey coloured tails, massive eyes and rounded ears, dormice are perhaps one of our most beloved – if least seen – animals. They are also our longest hibernating mammal, sometimes sleeping for up to three quarters of the year. Depending on the weather, they can fall asleep as early as October and not wake up until early May, which makes for an awful lot of snoozing! Even their name reflects their penchant for slumber, derived from the French dormir (meaning to sleep) or dormeuse (a sleeper).


Dormice live in woodlands and during spring and summer spend almost all of their time off the ground between the scrubby understorey in which they build their homes and high in the tree canopy. Their summer nests are built of grasses, stripped honeysuckle bark and fresh hazel leaves but by autumn, these homes will lie abandoned. After filling their bellies with protein-rich hazelnuts, dormice will head off to find a warmer site beneath logs, in a tussock of grass, at the base of a tree or even underground where the temperature is more constant. They snuggle themselves tightly into a ball of woven grass or bark covered with leaves or moss and sleep and sleep...


The secret to dozing for such a long period is high body fat and a slow metabolism. When the cold weather sets in, a healthy dormouse will be at least twice the weight it was in summer – 35 or 40g rather than 17g or so. Their body temperature falls to that of the woodland and their heart rate and breathing slows down to around a tenth of the normal rate so they use barely any energy at all. Nature is remarkable but there is a flaw; it means they are vulnerable if found by a predator because it can take quite some time to wake from such a deep sleep.


Dormice are a protected species and you need a licence to survey for their presence but if you want to look for signs of these elusive creatures, head to a woodland west of the Severn and look amongst the leaf litter for nuts that have had small bites taken from them. Dormice prefer to eat hazelnuts whilst they are still soft and green and having nibbled the shell to reach the kernel, they will drop it to the ground. If you happen to find a hazelnut with a perfectly round hole gnawed out of it, we’d love to hear from you - please send us the nutshell or take a couple of photos of it.



Common lizards are thinly scattered throughout Worcestershire and are scarce in our south eastern corner but by this time of year you’re unlikely to come across one no matter where you live. As reptiles, lizards are coldblooded (or ectothermic) meaning they are unable to create their own internal heat. Being reliant on the sun and their immediate environment for warmth means that during winter they have no choice but to hide away.


By November, all lizards will have found somewhere safe to snooze – often in the hollows of tree trunks or in cavities between and under rocks. Groups of lizards have been found hibernating together - presumably for warmth - and they will stay asleep until March or April, depending on the temperature.


Technically, the hibernation of cold-blooded animals is called brumation but it’s essentially a dormant state, loosely similar to the hibernation of mammals. Like other species, lizards prepare for brumation by stocking up on food, mainly worms, slugs and invertebrates. Once asleep, they too take advantage of milder patches of weather to temporarily shake off sleep and forage for food before hibernating once more. If only we could do the same...


Queen bumblebees

The common association of bumblebees, sunny days and brightly coloured flowers doesn’t entirely apply to the queen bumblebee, who spends much of her life underground, producing and caring for eggs, never again seeing the light of day once she has constructed her nest.


Some bumblebee queens will hibernate for up to nine months, almost three quarters of their life. It’s hardly surprising that winter is problematic for these nectarsupping, pollen-collecting insects, but hibernation does much more than protect them from the risk of starvation; it’s also a mechanism that guards against predation and disease.


New queens emerge in late summer just as the colony they are born into is in decline, mate with males and become fertilised. In autumn, the males and workers die, leaving the new queens as the only members of the colony who can survive the winter. They only do so by entering a state of true hibernation, waking in the spring when temperatures rise, ready to start brand new colonies.


Before hibernating, new queens will guzzle on pollen and nectar. This binge-drinking enables them to build reserves of energy that are stored in the body as fat, vital to helping them survive the winter. You can help them with this process by planting your garden with a succession of nectar-rich flowers that will bloom for many months of the year. Try mahonia, snowdrops, crocuses, winterflowering clematis and heather for late colour and nectar.


Queen bumblebees often choose to overwinter at the base of walls, in old mouse holes, plant pots or compost bins, under loose bark or amongst tree roots. However, their favourite site of all is near the top of a north-facing bank of earth in well-drained soil because it ensures they will not be exposed to winter sun, which could cause premature emergence – a potential disaster if temperatures plummet again and there is no food available.


During hibernation, bumblebees use a technique similar to the autometabolic control seen in mammals. If the temperature falls below a certain point, there is a danger that the fluids inside the queen’s cells could freeze, expand and cause her body to burst. Instead, glycerol production kicks in, automatically producing a substance that essentially acts as an anti-freeze, preventing ice crystals from forming in her cells. Even, or perhaps especially in winter, when so much of the natural world appears to be dormant, nature is amazing in so many ways.


Did you know?


Worcestershire Wildlife Trust is celebrating its 50th birthday this year. We’d like you to join in with our celebrations by helping to turn Worcestershire wild.


We’re asking you to Pledge a Patch for wildlife


Do you know someone who does amazing things for wildlife? Why not nominate them to become a Wildlife Hero?


Why not watch our 50th birthday video, featuring some of the 9935 species of wildlife that have been recorded on our nature reserves



For daily updates about wildlife around the county please follow us on twitter @WorcsWT

Tel: 01905 754919




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