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.
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.
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.
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.