The Bat Detective World Tour – join us soon!

Bat Detective has now been running for over three years, and all the input from our community of citizen scientists has been invaluable in helping us to develop machine learning algorithms for detecting bat calls in audio recordings – so thank you! As we explained in our recent post about our current research, adding more annotated data – and from a wider variety of recorded sound environments – will further improve the accuracy and reliability of our bat detector software. This will bring us closer to our goal of creating smart automated tools for monitoring global bat populations, which we hope will in turn help us to learn more about how human activities are affecting the earth’s ecosystems.

So we’re about to take Bat Detective on a World Tour, and we’re asking for your help in searching for bat calls in recordings from across the globe.

Since 2005 the amazing groups of volunteers and researchers on the iBats monitoring programme have been recording audio bat surveys in places ranging from the UK to Japan, North America to sub-Saharan Africa — each with their own distinct environmental soundscapes and unique selection of bat species. So far, however, the audio snapshots we’ve uploaded to Bat Detective have only been those from Eastern Europe. This means we still have lots of new data from all over the world in need of exploring and annotating, all of which will build into improving our automated bat detectors.

All countries where iBats surveys have been carried out to date (data:

All countries where iBats surveys have been carried out to date (data:

So throughout the World Tour we’ll be travelling from country to country, regularly uploading new sets of audio data from a selection of places where iBats volunteers have surveyed. We’ll begin in the UK, where the Bat Detective team are based, before jetting across the globe to search for bats in countries in Africa, North America, Australia and Asia. And as we go we’ll be adding posts to this blog, reporting on where and when the surveys were recorded, and highlighting some of the local bat species (and other curious sonic inhabitants) you can expect to encounter in each location.

Keep an eye on the Bat Detective blog for dates, news and updates as we progress through the tour. And until our travels start in a few weeks’ time, you can still help us track down bats in our current Eastern European data – visit the Bat Detective site to get searching. Thank you for your contributions over the last three years, and we hope you’ll enjoy helping us to search for bats worldwide!

Bat Detective research update – and stay tuned!

This week it’s our birthday! It’s been exactly three years since we first launched the Bat Detective project on 1st October 2012. Since then we’ve had an amazing response from our community of citizen scientist bat detectives, with over 94,000 unique audio snapshots explored by nearly 4,000 volunteers, and more than 11,000 bat calls discovered.

All the hard work you’ve put in so far has been invaluable. Using the data from Bat Detective, we’ve been developing computer algorithms that can automatically search for and detect bat calls in audio recordings with a very good success rate. To do this we’ve taken advantage of recent rapid improvements in machine learning technology for recognising complex patterns within data — such as the distinctive shapes of bat calls.

We’ve had great results so far, thanks to all the audio data the bat detective community has searched through, and all the calls you’ve identified. The majority of those have been searching calls (over 7,000), but you’ve also labelled over 2,000 each of the more rarely recorded social and feeding calls. We’ve used this annotated data to train our machine learning algorithms, by showing them thousands of examples of what bat calls look and sound like. This enables them to better tell apart the sounds we’re interested in from other background sound, such as insect calls and mechanical noise.

We’re now at the stage where we can use these algorithms to detect bat calls throughout the millions of recordings collected through the iBats monitoring project. What this means is that we’re a key step closer to developing automated software for accurately detecting and species-identifying bat calls from recorded audio — a vital move towards a global monitoring programme for bat populations. To read more in-depth summaries of the work our team members have been doing towards that goal, see our recent blog post for Methods In Ecology & Evolution.

This graph shows how well our algorithms are currently performing at finding known bat calls within a large set of audio data that we’ve already annotated. The closer the curve reaches to the top right of the graph, the better the results we’re getting — this means we’re maximising the proportion of the bat calls detected within the audio (increasing the recall) while minimising the number of non-bat sounds that are incorrectly classified as bat calls (improving the precision). When we use four times as much data from Bat Detective to train the algorithms (shown as a green line), we get a large improvement in performance compared to when we use much smaller amounts of data (shown as the blue and purple lines).


So the more data we can use to train our algorithms, the more accurate and reliable they will be. This will allow them to more successfully detect even calls recorded in challenging acoustic conditions, when there’s lots of background noise or the bats are far away from the detector — those trickier cases where they’re failing now. That’s why the ongoing help from the bat detective community is so valuable for our research. So later this month we’ll be announcing some new developments in the Bat Detective project, where you can help us search for bat calls in recordings from all around the globe — stay tuned for more information very soon!

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.




FAQs & Feedback

By Kate E. Jones and Kim Mroz

The Bat Detective project has passed its one-month anniversary! Since the launch, everyone who’s gotten involved has been fantastic. We’ve also had quite a lot of press coverage including that on the BBC News website; interviews on BBC Radio 4’s Material World Programme, Irish Radio, BBC World News; and a podcast for The Guardian.

Since our launch (up until Halloween), we’ve had 671 of you register with the site to explore the data our iBats volunteers recorded from Bulgaria. In total you helped us look at 18,729 snapshots and you provided 73,421 classifications – amazing! You found 12,653 bat calls in our Bulgarian data and also 22,275 insect calls and 23,003 machine sounds. We expected that a lot of the bat calls found would those ‘searching’ calls made when a bat is navigating around, and that is indeed the case (8,821 calls or 70% of the total). However the rest of them were classified as feeding calls (1,591) and a really impressive 2,239 calls were social. This is really exciting as comparatively little is known about social calls and this is first time that they have been recorded over such a large area.

We have been really amazed by how much support you have given us and many of you have done thousands of classifications each, for example one person provided over 9,000 classifications! On Halloween we released the Romanian data which of course includes those recordings made in Transylvania (home of Bram Stoker’s Dracula)! Despite what you may have heard about the legend of Dracula, you will not hear any vampire bats (bats that feed on blood) in the recordings. In fact there are only 3 species of ‘vampire’ bats out of over 1200 bat species in total with only one species known to associated with humans and they all live in South America. However, some exciting species that you might hear in the recordings include the Schreiber’s bent-wing bat (Miniopterus schreibersii), which is one of most threatened species in Europe and the European free-tailed bat (Tadarida teniotis) which might possibly be one of the smelliest!

A huge thank you for those of you that agreed to become moderators on the Bat Detective talk and helped field all the questions! There is a constant demand for more information, and you have given us lots of useful feedback about the site. We’ve noticed particular questions about the recordings (and the bats within them) keep cropping up and we have answered some of the most commonly asked questions below, which we would be happy to hear your thoughts about! That’s it for now, watch out for the Transylvanian report coming in a few weeks!


  1. How can we hear the high frequencies?
    Rob covered in his blog how the volunteers used ultrasound microphones to record the sounds beyond our hearing. These are then played back at a much slower speed to be recorded to the hard-drive, which is what we’re classifying here on… So 0.3 seconds of sound beyond our feeble hearing becomes 3 seconds of audible calls!
  2. Why can I hear frogs, birds and tigers, but no button to tag them?
    The recordings were all made across Europe shortly after sunset, and have been time-expanded (see FAQ #1). This means that it’s very unlikely you’re actually hearing tigers or birds, and if you were then they wouldn’t sound like you’d expect! Instead, we have chirpy bats and roaring insects, whose calls have been lowered in pitch and lengthened in time. So if you hear a noise that sounds familiar, you have to think about whether it would sound as familiar if it was 10 times higher and quicker!
  3. More examples? I’m not seeing many bats!
    The examples we’ve included in the field guide are particularly loud, clean sounds to help with your classifications. However, there isn’t enough room to include all variations of bat, insect and machine sounds! It could be that you’re over-looking the different, slightly obscured or quiet calls … you might like to check out the collections that users have made for more (possibly noisier) examples of interesting sounds!
  4. Is this a bat or an insect?
    Clicky Insect

    Fig. 1: Bat or Insect? … Insect!

    There are certain insects sounds (see Fig. 1) that masquerade as bat feeding calls (scroll down in the link) in the spectrograms, and there’s a general rule to help with these. Does the sound have a clicky or a chirpy quality? If it’s a clicky sound, then this is almost certainly an insect!

  5. If you’re only interested in bats, should I bother with labelling insects and machine sounds?
    Yes, please! We’re hoping to branch out into insects too; it would be a shame to waste all of this fantastic data. On the other hand, flagging machine noise can help tremendously with data quality control.
  6. What happens if I realise I’ve made mistakes? No back button?!
    It’s okay! Don’t worry! We obviously appreciate the care you’re taking with the tagging, but if you happen to miss something or you later disagree with your own tag then in the long-run it shouldn’t matter. Hopefully other users will spot these things too and everyone’s opinion will balance out to good classifications!
  7. What should I do with harmonics?
    Most naturally-made sound will contain more than one harmonic. Bat calls and insect sounds are no different!

    Fig. 2: Harmonics contain information too!

    Sometimes these harmonics are very quiet, and may not even reach the microphone at all (see Tim’s blog) but if there is a nice distinct harmonic (e.g., Fig. 2) then there’s no harm in marking it. Feel free to make a separate frequency range to let us know about harmonics.
  8. What are these odd un-cut recordings?
    Rob’s blog discusses how the processing of an evening’s recordings is meant to work, but sometimes our automated methods break down. Instead of only getting lovely 3 second snippets, there are also a few crazy recordings floating around … you can see some examples here! Don’t worry about these; just ask for another sound (sorry!).
  9. Audio doesn’t work … help?
    The site currently relies on Flash to play the audio recordings. If you’re having problems while using a major browser (e.g., Firefox, IE, Chrome) you may need to update your browser or Flash install to use the latest version. If you’re still having problems, then please let us know on the Help boards.
  10. I’m not sure about something, what should I do?
    Ask us! If you have a general topic in mind, you can start a discussion on the Science, Chat or Help boards or see if someone else beat you to it. If a particular sound has you stumped then Talk about it! The science team, moderators and other users may be just as stumped as you, but (hopefully) they might just have an answer!


We’re very appreciative of all of the feedback you’ve provided, which mostly concerns the mechanics of the Bat Detective site. We’re now at the stage of having a think on what changes we can make to allow you all to help us more easily.

  • Improve the tutorial and guide terminology … and the tutorial itself!
    The tutorial is at the top of our list of improvements. Hopefully a dedicated page containing a tutorial video, call guide and site-guide will make it easier for new and old users alike to find answers to their questions, and feel more confident while helping Bat Detective. Watch this space!
  • Add frequency scales on talk images.
    This is also something that we’re very keen to add ourselves. Discussing recordings in Talk will certainly be a lot easier with some reference to frequencies!
  • Confirmation button after selecting ‘Next Sound’.
    Several users have noted how other Zooniverse projects (e.g., MoonZoo) have some form of confirmation request when the ‘Next Sound’ button is hit while classifying. This would prevent slightly over-enthusiastic clicking leading to missed recordings, and is definitely something that’s possible.
  • ‘Did you spot this?’ sounds.
    So you can check how well you’re spotting the bats and insects, it has been suggested that every now and then we could give you an already classified sound to look at, and then point out the calls to see if we agree. Another great idea that we can filch (thanks Planet Hunters)!

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!


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