Do bats hibernate in winter? And more bat facts

You’re not likely to see many bats through the winter season. This isn’t just down to their nocturnal nature, it's also because they hibernate during the colder months. 

Read on to discover how they do it and learn more interesting facts about six of the UK's bat species.

When do bats begin to hibernate?

Bats enter hibernation in November and may not be fully active again until mid-May. While in this state of torpor, bats lower their body temperature and their metabolic rate slows.

This means they use less energy and can survive on the fat they have stored up, rather than expending vast amounts of energy in the cold weather searching for sparse food.

If you spot a bat before the weather gets warmer, it’s probably been rudely disturbed and is looking for a snack before getting back to sleep.

Where do bats hibernate?

As autumn turns to winter, bats are on the lookout for a comfy roost – a nook or cranny they can hibernate in over winter. You might think all bats hang out in caves but around three quarters of UK bats have evolved to roost in trees. 

They are not able to bore holes or build nests, so instead they make use of whatever gaps they can find. They particularly like to roost in mature and veteran trees that are hollow from natural decay or have had cavities bored into them by other animals such as woodpeckers.

In areas which lack available tree habitat, bats often favour human structures. You might find them wedged into holes in old brick walls or in the roof of your house. Old barns and abandoned buildings are favoured spots to roost in.

Caves and old mine shafts can also provide good conditions for bats to winter in, as long as they have a constant temperature and are free from damp and frost.

To keep warm, bats will crawl into very small rock crevices, squeezing themselves into odd positions, including lying on their backs or sides, or even upside down!

Fascinating facts about six UK bats

Bats represent almost a quarter of all UK mammals, with 18 species in total, 17 of which breed on the British mainland. Remarkably, some species can live for more than 30 years. Here are six UK bat species who will be looking to keep snug over winter.

Common pipistrelle (Pipistrellus pipistrellus)

The UK’s most common bat species, common pipistrelles are crevice-dwelling bats that can be found roosting behind areas of loose bark or within splits or rot holes. They’re well adapted to both rural and urban habitats, often appearing in gardens.

You can identify common pipistrelles by their erratic, twisting flight.

• Length: up to 5cm

• Wingspan: up to 23cm

• Weight: up to 8g

Brown long-eared bats (Plecotus auritus)

Brown long-eared bats will look for roosts that are lower to the ground and more cluttered with vegetation, unlike other species. They favour deciduous woodland, picking insects off the leaves and bark as they flit through the trees.  

You can identify brown long-eared bats by their very large ears and slow, hovering flight, which makes them look a bit like a large butterfly.

• Length: 3.7–5.2cm 

• Wingspan: 20–30cm

• Weight: 6–12g 

Noctule bat (Nyctalus noctula)

The UK’s largest bat makes its home in the trees all year round. Noctule bats favour those with rot and woodpecker holes, with males defending the best roosts to help attract females during mating season.

You can identify noctule bats by their strong, fast flight and golden-brown fur. If you see a bat flying in a straight line, high overhead, it’s probably a noctule bat looking for prey in the canopy.

• Length: 3.7–4.8cm 

• Wingspan: 32–40cm 

• Weight: 18–40g 

Barbastelle bat (Barbastella barbastellus)

Barbastelle bats are commonly found within any splits of a tree or behind loose areas of bark. They typically roost in trees year round, normally in ancient deciduous woods with a substantial understorey.

Barbastelle bats are fast, agile flyers and live in a variety of habitats, looking for food in open spaces, under the canopy and swooping over water. A rare species, the barbastelle is mainly restricted to southern and central England and Wales.

• Length: 4–5.5cm 

• Wingspan: 26–29cm 

• Weight: 6–13g

Bechstein’s bat (Myotis bechsteinii)

Bechstein's bat is a very rare species that prefers to roost in old woodpecker holes. Records indicate that oak and ash are their favoured trees, particularly in wet woodland habitats with small streams and dense vegetation.

The UK population of Bechstein's bat has plummeted in line with the loss of ancient woodland, with the species now only found in parts of southern England and southeastern Wales.

• Length: 4.3–5.3cm 

• Wingspan: 25–30cm 

• Weight: 7–13g 

Natterer’s bat (Myotis nattereri)

Natterer’s bats like to roost in broadleaved woodland, hedgerows and tree lines alongside agricultural land. Their large, broad wings give them great manoeuvrability at low speed, meaning they can catch insects sitting on leaves or even pluck spiders straight from their webs.

The species is widespread in the UK, though less common in Scotland and Northern Ireland. It's sometimes known as the red-armed bat due to its pinkish limbs.

• Length: 4–5cm

• Wingspan: 24.5–30cm

• Weight: 7–12g

How you can help UK bats

One of the best ways to help our magnificent bat species this winter is to not disturb them. Nobody likes being woken up in the middle of a good sleep!

Another great way to help bats is to install a bat box. Though bat boxes can’t replace the natural cavities that trees provide, they could be a welcome home for bats through winter.

Bat boxes can be placed wherever you live. They’re great for any sized garden or on a balcony or roof.

Top tips for a successful bat box

If you're wondering where to place your bat box, remember:

• bat boxes should be draught proof and insulated to prevent damp

• they are best placed above ground, 4–5m high, in a sheltered spot that receives sun during the day

• you can use several boxes facing different directions to provide a range of roosting options.

Once a bat box is up, it’s illegal to open it without a licence, so let them roost in peace. It's also illegal to disturb bats that have snuck into your loft or roof.

If you find a sick or ailing bat, you should not approach or handle the animal. Please call the Bat Conservation Trust’s bat helpline – a real life bat signal.