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British bats: A beginner's guide

It’s almost time to start looking out for bats. The hibernation season is coming to a close, and they’re hungry and ready to feed.

Bats make up a huge portion of our resident mammal species, and are vital to our ecosystems. Yet many people have never seen a bat. They remain widespread, but their populations and habitat are dropping and they need help.

There are 17 species of bats living here in the UK. That’s almost a quarter of our resident mammals! Yet they’re one of our least noticed because not only are they nocturnal but they hibernate through the cold winter months. Here’s some of what they’ll be getting up to in the coming months, and some tips on how to spot them.

Quiet months

Hibernation slows down their metabolism but they still need energy to stay alive. Around this time of year, the fat reserves they need for this run out, and they need to find food. They begin to venture out of their winter roosts, using echolocation to catch their dinner.

Barbastelle bat
The barbastelle bat is
one of the UK's rarest bats
(Photo: C Robiller)

What they’re up to

The main focus for bats right now is fattening up. All British bat species are insectivorous – meaning they only eat insects.

Echolocation is a great hunting tool for bats as it can help them not only ‘see’ where the insects are but how fast they’re moving and in which direction. To do it, bats emit high-pitched vocalisations which reflect off objects around them and echo into the bats’ specialised ears. This helps the bats to fly straight to their food, scooping it up in their wings and feeding themselves.

Once they’ve put on a bit of weight, they’re in good condition to give birth. The females congregate in maternity roosts for this very reason. They feed their young on milk until they’re strong enough to fly themselves at around three weeks old. During this time, the males stay well away. They tend to roost by themselves, or sometimes in small colonies of just a few bats.

The two sexes mix again for breeding season between September and November. Males will put on extravagant flying displays to impress the females – gaining them a harem of up to ten mates! Bats undergo a process known as delayed implantation. The females’ eggs will get fertilised immediately but the embryo only starts to develop when hibernation ends four months later.

How to spot bats

Around 75% of all bat sightings are of pipistrelles. We have three species of pipistrelle: the common, the soprano and the Nathusius’. As the name suggests, the common pipistrelle is the most frequently seen. Each bat can eat up to 3,000 insects a night – giving you plenty of time to catch a glimpse.

  • Dusk is the perfect time to see them - They’re usually spotted around 20 minutes after sunset, during spring and summer, as the sky is still light enough to see their silhouettes
  • Look up - They may be some of our lower-flying bats but this still involves heights of up to 10 metres. Although you may be lucky to spot a low-flyer as close as 2 metres from the ground!
  • Stick to field boundaries - At dusk, insects tend to gather above trees and hedgerows that surround gardens and fields which draws the bats to these spots too. If you’re nearer to spaces lit with streetlights, you’ll also have a good chance to spot them
Pipistrelle bat
Have you spotted a
pipistrelle bat near you?
(Photo: Wikimedia Commons)

Don’t forget we have plenty of other species of bats to see, so keep your eyes open. You’ll be able to spot bats up to twice the size of pipistrelles depending on where and when you look. Our other most common species include the Daubenton’s and the noctule. The Daubenton’s bat emerges one hour after sunset and you’re most likely to see them flying low over still bodies of water. The noctule is a much higher flier, with characteristic steep dives to catch larger bugs.

Threats

Our bat populations are still pretty healthy but we have started seeing worrying declines. They may be widespread across the UK (depending on species) but habitat loss and disturbance is changing things.

All bats are easily disturbed when roosting and if this happens they will usually abandon their young. Agricultural practices and housing developments are also stripping away their natural habitat of trees and hedgerows. Without these, the bats will struggle to find adequate roosting sites and hunting grounds will see a drop in insect numbers.

Habitat fragmentation also breaks up usable habitat, separating populations. If colonies can no longer mix, there will be a drop in genetic diversity which will make the population more vulnerable to disease.

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How you can help

In an ideal world, we wouldn’t lose any of the vegetation crucial to bat success. If you own trees and hedgerows on your land, be sure to keep them around. But many of these are beyond individual control.

It always helps to set up bat boxes. There is a range of different types available to buy, or you can even make your own. These will offer a roosting site to smaller colonies and solitary males. As bats are so easily disturbed, it helps to make sure these are in quieter areas with trees nearby for cover.

You can also help by encouraging your local insect population. Planting wildflowers will attract them to your garden. Dandelions, bluebells and foxgloves are some of the best plants to attract an array of tasty bugs. Herb gardens can also work wonders, and provide you with fresh seasonings for your own meals!

Our bats are often overlooked, but lead interesting lives. Whilst widespread in the country, they suffer population decline and need a helping hand. Why not try one of the ideas above? Or get creative and come up with more ideas – the possibilities are endless!

This week there’s also an exciting opportunity to become a Bat Detective! This year’s British Science Week is all about bats, and they have a great project for you to get involved with. A huge bank of recorded bat calls can help you to work out which bats you’ve found near you.

You can also follow the conversation this week on Twitter with the #BSW16 hashtag