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Next stop on the World Tour: We’re in Ghana!

Welcome to the second stop on the Bat Detective World Tour! We’ve spent the past few weeks uploading audio data from surveys in the UK, where the Bat Detective team and the Bat Conservation Trust are based. During that time our team of citizen scientists have completed over 7500 classifications, so thank you for your work during the first leg of the world tour. You can learn more about how your input is helping us to improve our automated bat detector softwares at this recent blog post.

Now, just as the UK weather is getting colder, we’ve jetted off to warmer climes. We’ve just arrived in Ghana in tropical West Africa, a country with rich biodiversity and a range of amazing bat species, and an important agricultural producer of crops such as cocoa, sugar cane, rubber, palm oil and bananas. Bats are pollinators for some of these crops, including some mango, cocoa and banana species – one of the many important ‘ecosystem services‘ that they provide for humans.

Starting today, 30th November, over the coming weeks we’re asking our bat detectives to listen through audio recordings of bat surveys around Ghana’s capital city of Accra (shown on the map below), conducted in 2010 by iBats volunteers. Click here to visit the Bat Detective site now to start listening and classifying. As you might expect for a tropical country with high wildlife species diversity and associated acoustic variety within the environment, many of the sounds you’ll encounter in these data are markedly different from the European audio data we’ve previously hosted on Bat Detective. They include different insect species, as well as a variety of bat species with their own fascinating, complex calls.

Accra, where the Ghana world tour audio data were collected

One particular bat species is one of Accra’s most famous urban residents – the straw-coloured fruit bat (Eidolon helvum). Massive gatherings of up to a million individuals of this large species are known for roosting in trees near the centre of the city, before spectacularly taking off at dusk and travelling outward en masse to forage. However, you won’t hear them in our Bat Detective recordings, as they’re part of the fruit bat family Pteropodidae, which do not use true ultrasonic echolocation to communicate and search for food. However, there are a wealth of echolocating bat species in this region of Africa that you might encounter while searching our Ghana data, from the widespread Angolan free-tailed bat and Noack’s roundleaf bat, to the distinctive yellow-winged bat (pictured below) a member of the false vampire bat family.

Although the Ghana recordings are often quite acoustically different to our previous European data, the same general rules for recognising different sounds still apply. Bat calls sound like a chirp, squeak or whistle, and usually show up on the spectrogram as defined pulses of sound, sometimes with additional harmonics at higher frequencies. The following two images are examples of bat calls from the Ghana data.



And the spectrogram below contains two distinct sets of bat calls from two individuals: one series of almost vertical calls at slightly lower frequency; and a separate, very bright horizontal call with two harmonics stacked at higher frequencies.


If you’re lucky you might also come across a ‘feeding buzz’ – a distinctive sequence of call pulses that gradually become closer and closer together as the bat approaches its prey, as shown in the clip below.


Insects often make rhythmic calls which can sound like a serrated rattling, buzzing or hooting. Visually they often look like repeated figures across the spectrogram at lower frequency than bat calls, such as in the following two clips. They can also often sound like car alarms or like distinct pulses within a messy spectrogram.



You might also encounter both insect calls and bat calls in the same clip, such as in the example below, where a bat call is shown in the blue outline, and the insect calls in green. You can usually tell the two apart by listening carefully for the bat’s distinctive chirping or whistling tone.


More detailed information and examples of different sound types are provided in the key at the bottom of the Bat Detective ‘classify’ page.

But if you’re still unsure about whether a sound is a bat or not – or even if you’ve just discovered a particularly strange or interesting clip that you want to draw attention to – just use the Talk function to discuss the call with others in the Bat Detective community and our researchers.

We hope you’ll enjoy searching for bat calls in our Ghana data over the coming few weeks. We’ll be staying in Africa for the next stop on the tour too, so keep an eye on this blog and our Twitter and Facebook pages for future news announcements.

Yellow-winged bat (photo by sandralee, displayed under Creative Commons licensing)

Yellow-winged bat (photo by sandralee, displayed under Creative Commons licensing)

Bat Detective World Tour begins! Welcome to the UK

The Bat Detective World Tour starts today! Over the next few months we’ll be regularly uploading new sets of data to Bat Detective from different countries across the globe – from Europe to Africa, the Americas and Asia – each with its own selection of bat species alongside other acoustic inhabitants. Today we begin our global bat search in the United Kingdom, home of the Bat Detective team and the Bat Conservation Trust (BCT). We’ve just uploaded a brand new set of audio recordings from the UK for our citizen scientists to explore, so to get involved, head across to the Bat Detective site right now.

These recordings are from surveys carried out across Great Britain between 2005 and 2010 – you can see their locations on the map below. The sounds you can expect to hear in these recordings are similar to the earlier Bat Detective data from Eastern Europe, including many of the same bat species, such as pipistrelles, serotines and noctule bats. Found across much of continental Europe, these are also among the UK’s most widespread bats, some of which you’ll probably have seen or heard through a detector if you’ve ever been out for a British bat walk or survey.

They’re also among the main species surveyed in the UK as part of the BCT’s National Bat Monitoring Programme (NBMP), a huge ongoing citizen science project that has been running for over 17 years. Carried out by thousands of volunteers who are trained to recognise different species calls using acoustic bat detectors, it’s a great example of how citizen science can make a real difference to our understanding of the status of wildlife populations.

iBats UK survey locations, which provided data for the UK segment of the Bat Detective World Tour

Survey locations from iBats UK project, which provided audio data for the UK segment of the Bat Detective World Tour.

You can read the most recent results report from the NBMP here. A paper by the NBMP team published in the scientific journal Biological Conservation in early 2015 showed that the long-term data collected by their volunteers could detect changes in bat populations equivalent to a Red Alert (a decline of 50% in 25 years). They also suggested that the current outlook for UK bat populations seems to be relatively positive, with most bat species showing either stable or slightly increasing population trends between 1997 and 2012 – promising initial news after the declines suffered by many species during the 20th century. These results should continue to assist in future monitoring of UK bat populations, and are evidence that citizen monitoring programmes can and do provide scientifically useful data for informing conservation. To find out more about the NBMP and how you can get involved, click here to head to their website.

Our goal with Bat Detective and iBats is to use similar citizen science-led approaches to develop new tools for monitoring bats on a global scale, while taking advantage of new advances in technology. As we’ve explained in previous blog posts, the data collected by iBats volunteers and labelled by Bat Detective users is helping us to develop automated software for reliably detecting and species-identifying surveyed bats. This will allow the analysis of massive amounts of survey data to be standardised across all volunteers and countries, thus increasing the usefulness of the data for drawing scientific conclusions. To read more about why collecting this data is important, read our earlier blog posts, here and here.

As well as some of our better-known bat species, while you’re exploring the UK Bat Detective data, you might also encounter a rather more uncommon visitor – the migratory Nathusius’ pipistrelle (Pipistrellus nathusii), which was named BatLife Europe’s bat of the year in 2014. Much is still unknown about the presence of this tiny traveller in the UK, since it’s rarely encountered here, although some individuals are known to be resident all year round. But researchers are finding increasing evidence to suggest that this species frequently crosses the North Sea between the UK and mainland Europe. In 2013 one individual that had originally been identity ringed near Bristol was found in the Netherlands, a direct distance of nearly 600 kilometres – a colossal trip for an animal that’s only about the size of a human thumb!

BCT are currently running a Nathusius’ pipistrelle project in the UK. Learning more about this amazing species will be important for reducing the potential human hazards it might encounter on its migrations, for example by placing wind turbines away from its main travel routes. So while searching the UK Bat Detective data you might be lucky and hear one too – for information on how to identify Nathusius’ pipistrelle from their calls, visit the BCT site.

Good luck and happy searching during this first leg of the Bat Detective World Tour! If you’re unsure about whether the sounds you’re hearing are bats or not – or just want to highlight something interesting you’ve found – visit the Talk section of the website to discuss your findings with the Bat Detective community.

Nathusius' pipstrelle

Nathusius’ pipistrelle (photo via Wikipedia).

Bat Appreciation Day

Today is Bat Appreciation Day!

To celebrate we have written a blog post for Methods in Ecology and Evolution. We mention the great work that has already been performed by the Bat Detectives and give a round-up of the latest methodological advances in bat monitoring and what we hope to see in the next few years.

The post can be found here:

The Funnel-eared bat (Natalus stramineus) – © Veronica Zamora-Gutierrez

The Funnel-eared bat (Natalus stramineus) – © Veronica Zamora-Gutierrez

Progress to Date and New Data

The bat detective project has been running for over a year and a half and we have had a fantastic response from our community of detectives. In this blog post we are going to give a short summary of all the hard work that has been performed by the community to date.

As of this month we have had over 310,000 classifications on the site. Close to  2,400 registered users have viewed and listen to over 70,000 unique audio snapshots. Of the 70,000, 8,350 were labelled as containing bat calls and 35,000 as having insects. Our top two most prolific detectives have viewed over 40,000 snapshots each!

With over half a million recordings in total, there is still a long way to go. In a future blog post we will talk about our current research into building computer algorithms which will help us find bat calls automatically. These algorithms rely on being shown many examples of what a bat call sounds like so they can try and learn what makes them different from all the other sounds we capture. That is why the continued help from the community is so invaluable.

We have just uploaded some new data to the site. So best of luck!

bat Detective

Do you enjoy being a part of Bat Detective?

UCLIC Would you be willing to talk about your experience as part of a Skype or phone interview? At the UCL Interaction Centre, Dr Charlene Jennett and Zoya Ajani are hoping to understand more about the experiences of Bat Detective volunteers – how did you find out about the project and what motivates you to take part? By understanding your experience at Bat Detective, Charlene and Zoya are hoping to gain valuable insights into ways to improve online citizen science projects in the future.

CyberlabThis work is being conducted as part of the Citizen Cyberlab project, a three-year EU project that aims to study and enhance the opportunities for learning and creativity available to participants in online citizen science projects.

CharleneZoyaInterviews are between 30 mins to 1 hour, and participants will be rewarded with an Amazon gift voucher. If you think you would like to be interviewed, please email Charlene for more information.

Hang out with the Bat Detective team


Hopefully the link above should take you to the Youtube page for the first ever Bat Detective hangout, which will start just after 7pm GMT. Once we’re done, that should magically transform into a link so you can catch up with the Bat Detective team again and again and again.




How many bats are there?

By Tim Lucas

Knowing whether bat populations are growing or shrinking tells us about the health of the bat population (see Dr Kate Barlow’s blog). It also gives us information about the health of the ecosystem in general, as discussed by Dr Robin Freeman. However, these are relative measures; are there more bats this year than last year? Sometimes we want to know an actual number. Are there a thousand bats? Ten thousand? A million?

For example, if we are trying to conserve a rare bat species we need to estimate the actual number of bats. At very low population sizes inbreeding starts to become a significant problem for conservation. Ten percent fewer bats than last year could mean a decrease from 100,000 bats to  90,000 bats or it could mean a decrease from 1,000 to 900 bats. While both situations are worrying, only in the later case do we need to start considering genetic inbreeding.

So how do we estimate the size of a bat population from our acoustic surveys? This is not a simple problem. If I go out with my bat detector and count 200 bats, what does this mean? Maybe I actually detected every single bat making the population size only 200. Maybe I detected one percent of all bats making the population size 20,000.

In essence the problem is to work out how many bats you expect to detect per hour of surveying. This depends on a number of factors.  The flight speed of a species is important. You are more likely to come into contact with bats that fly quickly. If you sit by a motorway you will see more cars than if you sat by a country lane even if the total number of cars is the same on each road.

Secondly the actual area of land that you are surveying is clearly important and this depends on the distance within which you can detect a bat. Louder bats can be detected from further away, just as larger animals can be seen from further away. This means you are surveying a larger area if you are looking for loud species than if you were looking for quiet species.

The frequency of the bat call also matters as high frequency sounds travel less far than low frequency sounds.


As an example, the spectrogram shown has a loud ‘hockey stick’ call at about 25kHz but also a quieter harmonic above it, at about 60 kHz. Even without considering through use of seo services that the harmonic is quieter (it is less bright on the spectrogram) it will travel about half the distance of the lower frequency call. The maths to work out these distances is long and boring so I hope you don’t mind me not showing my working!

So, if we can make a good guess of how large an area we are actually surveying we can work out what proportion of the bat population we saw. Did we survey 1% of land in Europe, or 0.001% and so did we see 1% of the bat population, or 0.001%. Using this information and information about how fast bats fly we can try to work out how many bats there are in total and use this information to  conserve them as best we can.

The importance of bat base-lines

By Dr. Elizabeth Boakes

If you were to look in a mammal field guide you might think we already know where different bat species can be found. However, our knowledge of species distributions is often behind times. Information on changes in a species’ range is usually of higher quality in species with small ranges, simply because these species are easier to monitor. There is therefore a real risk that declines in more widespread species may be overlooked, particularly if these declines occur in the middle rather than the edge, of a species’ range. Indeed, a species range size, as measured by its borders, may remain constant for a long period of time even if local extinctions are occurring throughout its centre, a process known as fragmentation. The species final collapse toward extinction may be so rapid that sufficient conservation intervention cannot be made in time to save the species (see figure).

Range declines can appear stable over time, making possible declines towards the centre of the range.

Widespread species also tend to be overlooked by scientists who, with limited time and funds, necessarily have to focus attention on species already known to be threatened. In the last 30 years this has led to a real dearth of data on more common species. This is extremely worrying since it means that without these ‘biodiversity base-lines’, ecologists will struggle to map declines in previously widespread species and hence may not be able to find their underlying causes. If we do not knowwy a species is declining it makes it far harder, if not impossible, to reverse that decline.

With the help of volunteers, monitoring widespread species across their range becomes much more tractable and means that a better understanding of species ranges over time can be constructed which will prove invaluable in the future should that species start to decline. Volunteer records are as essential to conservation management as museum collections and I like to think of volunteers as curators of nature. In our rapidly changing world it is hard to predict what species will become threatened next but if we are armed with a repository of distribution data we can hope to notice and respond to these changes as quickly as possible. The Bat Detective project, and your key contributions to unlocking the data wtihin it, are therefore a fantastic conservation resource, not just for today but for decades of future bat custodians.

Indicator species and trends

Bats are often referred to as ‘indicator species’ this signifies that a species is considered indicative of some underlying environmental characteristic. As Kate discussed last week, not only do Bats provide us with essential services (such as pest control and pollination), they also indicate how the nocturnal ecosystems they inhabit are faring. A healthy ecosystem should be able to support bats and changes in bat abundance and distribution may indicate underlying changes to that ecosystem (thus ‘indicator’). Bats are also known to be particular sensitive to such changes and thus may make a more effective indicator than other species.

Figure 1 – Estimates for the abundance of pipistrelle species 1978 – 1992. Source Bat Conservation Trust, via JNCC (

The Joint Nature Conservation Committee has adopted six widespread bat species as an indicator of mammals in the wider countryside (see ‘Indicators in your pocket’: Since 1978, records indicate that populations have declined dramatically, but more recent conservation efforts and monitoring programs have helped to produce more positive recent trends. However, in the context of the longer term declines, much more needs to be done to help bat species maintain these gains, and hopefully increase further.

How does this relate to the Bat Detective project? Well, much of these data are from well-established UK monitoring programs, and we have a less clear picture of how bats are faring across Europe and worldwide. The identification of bat calls that you’re providing through will allow us to then identify the species that make these calls and then develop a much clearer picture of the distribution and abundance of these species throughout Europe (and eventually the world!).

Figure 2 – Trends in widespread bat populations, 1999 to 2011. Source Bat Conservation Trust, via JNCC (


So keep up the amazing work! Your wonderful efforts will help us to identify species that are at risk and areas that need better conservation and management!

Why do we need to monitor bats?

Dr Kate Barlow, Head of Monitoring, Bat Conservation Trust

For one we need our bats! Bats are an important part of our ecosystems not least because they provide us with all sorts of useful services around the world, including pest control and pollination. And if we know we need bats surely it is a good idea to see how they are doing?

Brown long-eared bat

Brown long-eared bat/ Bat Conservation Trust

Over the last century bat populations suffered severe declines, both in the UK and across Europe. A combination of different pressures on bats including agricultural intensification, increasing building and development, direct persecution and use of pesticides including timber treatments which severely affected some bats resulted in significant losses of bats over a number of decades. Today all bats and their roosts are protected by law both in the UK and across Europe. To ensure that protection is effective, to find out how well we are doing at preventing further declines in bat populations, and to attempt to improve habitats for bats so that numbers can recover, we need to know how well our bat populations are doing, and this is where monitoring comes in. The Bat Conservation Trust runs a National Bat Monitoring Programme which relies on an army of dedicated bat volunteers spread across the UK who go out in force every year carrying out our bat surveys and sending us data on bats in their areas. We can then put all of this information together to see how well bat populations are faring at the UK level and use the results to ensure conservation work is focused where it is needed. But if that wasn’t reason enough to monitor bat populations, there is more….

What surprises a lot people is the diversity of bat species around the world, from fruit bats in Australia to tiny pipistrelles in the UK. In fact bats account for about a fifth of the world’s mammal species, that’s well over a 1000 different species of bats! In the UK we have 17 different breeding species of bat. They all are active at night, flying around our cities and countryside searching for and catching their insect prey. Each species has different needs, some roost in buildings others in trees, different bats spend their time foraging in different habitats and eat different insects. The common pipistrelle, one of our smallest and most widespread bats, can be seen busily flitting about around dusk in many gardens and parks across the country, feed on tiny flies, hoovering up thousands of midges and mosquitoes every night. Some of our bigger bats like the noctule need a bigger meal to keep them going and will eat larger insects like beetles, and some bat species have very particular needs and will only be found in the best areas of old woodlands where their favourite moth food can also be found. Different bats, in different habitats eating lots of different insects means that bats can tell us a lot about habitats and ecosystems. And as bats are found across the world and sensitive to change we can try to use bats to track global change. In short if we know how bats are doing we know more about the state of our planet.

Bat detecting

Bat detecting/ Bat Conservation Trust.

Bat monitoring can be done in a number of different ways and keen bat workers can be found carrying out bat surveys at all times of year – standing outside buildings on summer evenings carefully counting bats as they head out from their roosts to feed; clambering around winter bat sites peering into cracks and crevices to search for hibernating bats; or wandering around the countryside armed with bat detectors looking for bats in different habitats. All these different monitoring methods produce a lot of data, and the data needs to be entered, stored, processed and analysed. The Bat Detective website will help us to analyse bat data and develop more efficient methods to process the vast amount of data our monitoring produces.

So going back to my question on why it is important to monitor bats, I could simply say because it keeps me in work! Or because I love bats. But there are so many better reasons for us to know how our fascinating and furry friends of the night are faring, from assessing the health of habitats to monitoring global change, there is still so much to learn from bats.