Bats: a success under threat

With around 1200 species recorded worldwide, approximately one quarter of all known mammals are bats – only the rodents are more speciose. Bats occur almost everywhere on land, and are present on all continents with the exception of Antarctica.

Bats belong to the order Chiroptera, meaning ‘hand-wing’, which is split into the sub-orders Megachiroptera - the Old World fruit bats - and Microchiroptera. All seventeen resident British species are Microchiropterans. Two - the Greater horseshoe Rhinolophus ferrumequinum and the Lesser horseshoe R. hipposideros - belong to the family Rhinolophidae, and the remainder belong to Vespertilionidae; which is the largest mammalian family after Muridae (the Old World rats and mice). Yet, despite their evolutionary success, an estimated 15 percent of all bat species worldwide are now threatened with extinction by habitat loss, persecution and disease; and in the UK, all native species require protection from both national and international legislation.

Northern extremes

Being a small insectivorous mammal, living in a temperate climate has its drawbacks. Firstly, food supply is seasonal; secondly, being so small, much body heat is lost to the surrounding cooler air. Our bats overcome this by entering periods of torpor and hibernation in order to conserve energy. However, this strategy has its limits and there still exists a gradual loss in species diversity with increasing latitude. For example, in Devon, in the south-west of the country, sixteen species have been recorded (1); whilst up here in Durham, eleven species have been recorded – one of which remains unverified, and only eight of which are known to breed (2). Nevertheless, this figure may come as a surprise to many, especially those who are not even aware that bats are around us – sometimes quite literally!

Detecting bats

Bats are notoriously difficult to follow and to study, owing to their diminutive stature, nocturnal lifestyle and accomplished flying skills. Even here in the UK, with our rich history in the natural sciences, bats remain an enigma, and there is still very much to learn of their behaviour and ecology. However, there is an element of their anatomy and physiology that, in recent years, we have been able to exploit in order to begin scratching at the surface – this is the process of echolocation.

All Microchiropteran bats possess the ability to orientate by echolocation; which they achieve by emitting sounds through their mouths or noses and detecting the returning echo from solid objects. The average amplitude, duration and frequency of calls differ between species; so, in theory, we should be able to unmask a bat’s identity by measuring these parameters – if only it were always that simple! There is much overlap in the call parameters of closely-related species, and to add to the confusion, an individual will vary its call according to its foraging strategy and the habitat it is using. As a result, equipment and software has become increasingly sophisticated (and expensive) in order to assist a growing army of demanding bat hunters. However, detecting and identifying bats needn’t break the bank, and much can be achieved using a (relatively) inexpensive frequency division bat detector, an MP3 recorder and freely-available sound analysis software.

The bats around our campus

The bat year begins with the end of hibernation, usually in March or April. On at least one evening in each month since March, I have taken a stroll around the perimeter of Great High Wood, stopping briefly at strategic points along the way, such as ponds, pasture and edge habitat. I listen to my detector over headphones and make notes of when and where I hear a bat. In the background, my MP3 recorder dutifully records everything that the detector picks up. Once indoors, the sound file can be downloaded to a computer and analysed using the sound analysis software. This is invaluable for verifying identifications made in the field, as well as for making sense of unidentified calls, and sometimes, for finding calls that were missed completely!

It is difficult to put an exact number on the total species I have recorded around campus – it could be as much as nine or as few as five. This is mainly because the echolocation calls of bats of the genus Myotis are very difficult to tease apart - even when viewed on a sonogram; and far more experienced ‘batters’ than I will often record them only as ‘Myotis sp.’. Below is a round-up of the species recorded, whether positively or potentially identified, along with both 'visual' and acoustic examples of their calls.

Myotis species

It is possible that I have recorded up to four Myotis species; but in reality, it is more likely to be two or three. The Whiskered Bat (Myotis mystacinus) and Natterer’s Bat (M. nattereri) are likely suspects, and, although strongly associated with water-bodies, Daubenton’s Bat (M. daubentonii) will also utilise the woodland. Brandt’s Bat (M. brandtii) is the fourth Myotis species recorded in County Durham, but is much rarer.

The sonogram and soundfile below are of the same echolocating Myotis individual, and are an example of how difficult it can be to separate the species of this genus by their calls alone; as certain parameters best fit one species, whilst others best fit another. What’s more, this recording was made in an open situation with no trees or other obstacles around, and the bat may have emitted a lower frequency range than it would have done in a cluttered environment. This is because it would not have needed to gain as much information about its immediate surroundings. It would take a braver (or more experienced) chiroptologist than myself to confidently identify this call to species-level!

Noctule (Nyctalus noctula)

With a wingspan comparable to that of a blackbird (Turdus merula), the noctule is Britain’s largest bat. However, its body-size is far smaller, and even the largest of individuals weigh less than half that of the bird. The noctule is a fast and efficient flyer, utilising open spaces to hawk for its insect prey. It is the earliest species to take wing in the evening, and can be seen (or heard) even before the sun has met the horizon. I recorded this species in the pasture around Houghall Farm just to the south of Great High Wood.

There is a second species in Britain that belongs to the genus Nyctalus – this is Leisler’s Bat (N. leisleri). A large Leisler’s individual is about the size of a small noctule. It emits the same ‘chip-chop’ echolocation call as the noctule, but, on average, it is a higher frequency. Back in mid-May, I made two separate recordings of calls with parameters that fit Leisler’s Bat very well – one in Houghall Farm pastures, and another in the grasslands around the Mountjoy Centre.  However, since then, I have been reliably informed that this species is very scarce in County Durham, and that the calls were more likely to be those of Noctule. Nevertheless, I am going to remain ‘on the fence’ about this one, and record it simply as Nyctalus sp.

The sonogram and the sound file below are both snippets taken from the Mountjoy grasslands recording, and include a Common Pipistrelle (Pipistrellus pipistrellus) followed closely by the Nyctalus.

Pipistrelles (Pipistrellus spp.)

I have recorded two pipistrelle species in and around Great High Wood – the Common Pipistrelle (Pipistrellus pipistrellus) and the Soprano Pipistrelle (P. pygmaeus). Aside from being our two commonest and most widespread species, these are also our two smallest; and, astonishingly, some individuals may weigh less than a two pence coin – or roughly the same as a Goldcrest (Regulus regulus; for those whose currency is birds). The two species are very similar and were identified as separate as recently as the 1990s; but with a little practice, they can be readily identified in the field by their echolocation calls – the peak frequency of the Common Pipistrelle being around 47kHz, and the Soprano around 55kHz (although there is some overlap around 50kHz).

The sonogram below shows an echolocating Soprano Pipistrelle (Pipistrellus pygmaeus), and demonstrates the classic ‘hockey stick’ shape of the pipistrelle’s call. There is a fair bit going on in the accompanying sound file; initially you may hear the feeding buzz – a ‘raspberry-like’ sound as the bat homes in on its prey. It is then joined by a second bat – also a Soprano Pipistrelle – and short scratchy or raspy sounds can be heard in the second half of the recording. These are social or contact calls made by the individuals communicating with each other, and are not used for echolocation.

Brown Long-eared Bat (Plecotus auritus)

After the Common and Soprano Pipistrelles, the Brown Long-eared Bat is probably Britain’s next most abundant species. However, it has a very quiet echolocation call, often described as a 'light purring' or 'like the clicks of a Geiger counter', and a bat must be no more than a few metres away in order to be picked up by the detector. Consequently, despite its common status, I have recorded this species relatively infrequently.

The Brown Long-eared bat’s short, broad wings are suited to slow, manoeuvrable flight, and it sometimes hovers using its enormous ears to listen for its moving prey before picking it from the surface of vegetation. The species’ main prey is moths, with which it is locked in a coevolutionary ‘arms-race’. Many moths have evolved the ability to hear an approaching bat’s ultrasound, which allows them time to take evasive action. However, aside from having a very quiet echolocation call, the bat’s huge ears and relatively large eyes (compared to those of other bats) are adaptations to hunt using sight and sound; thus, avoiding detection.

I have recorded this species at the Mountjoy Pond, Houghall Pond and along the edge of Great High Wood itself. There is also a known roost within Hollingside House in Hollingside Lane - which they share with Common and Soprano Pipistrelles and an as yet unidentified Myotis species. I was privileged to witness some of these species emerge from the building when I joined Durham Bat Group for a dusk survey in July.

The recording below was made at Houghall Pond to the south of Great High Wood; where, although it must have passed just above my head, the bat remained unseen.

Today I’m going to briefly chat about things to consider when buying camcorders for your research. I hope this provides a good start point for anyone wanting to film animals for research. As said in my previous entry, I am assuming that you are not going to use be able to afford very expensive cameras and you are looking to use the sort of equipment found at normal electronic stores.

The main thing to consider when choosing a camcorder is what you are hoping to film, and therefore what you’d want and need your camera to do. Say you want to film elephants from a few metres away- you probably don’t need a fantastic camera, although I’m sure it would help. If you wanted to film those elephants from miles away you may need something a bit better to let you pick out objects at a distance. In my case I needed to identify pollinators and which flowers they visit on lots of fireweed plants in the wild from one or two metres away. This meant I’d need affordable cameras (so I can have a few filming at any one time) with a good enough quality image to identify the species of fast moving bees and clearly show when they are visiting each flower. For this I got a bunch of cameras, but most were a Canon Legira HFR306 or HFR36.

The confusing thing about modern camcorders is that it can be difficult to work out what specifications are needed. Nobody wants to pay for something they don’t need, especially if you are on a limited research budget. Many manufactures make models that differ in only a few characteristics and it’s hard to tell which is good enough. Obviously if the difference between one camcorder model is one has wi-fi and night vision and the other doesn’t it’s easy to say if you need those things. However, as most camera specs are garbled nonsense to a lot of people, I'll do my best to explain what the main specifications mean and what effect they have.

Video quality

The first thing to consider is what video quality the camera can film in. Most cameras say something on the box that looks like ‘[seemingly random number]x[another seemingly random number] HD’ and lots of words like ‘FULL HD’ and ‘REAL HD’- these refer to the video quality the camera can do. Basically ignore FULL and REAL and look at the numbers, which refer to the width and height of the picture in pixels. Many camcorders can go as high as 1920x1080 (Full HD), which is generally pretty good (at time of writing) but you can get higher. Often these numbers are followed by letter either ‘p’ or ‘i’, which refer to how often the camera updates the video image (sometimes called scanning). ‘I’, or ‘interlaced scanning’, means the image is updated in alternating screens. ‘P’, or ‘progressive scanning’, means the image is updated every screen; this is generally better if you are filming fast moving objects and picking finer detail, whereas ‘i’ is fine for slower moving objects but might cause blurriness if used to film something very fast moving (like bee flight). It’s worth noting that most cameras can film in formats that are lower quality then the ones advertised on the box.

Zoom

Most cameras list the number of times it can zoom ‘optically’, with the lens, or ‘digitally’, by zooming into the recorded image. Normally once you enter digital zoom you get a loss in picture quality, though this usually isn’t that bad. If you can’t find how much optical zoom a camera can do, it’s written on the camera at the rim of the lens. 'Optical’ and ‘digital’ stabilisation of video images refers to how the camera compensates for shaking and keeps the image still; this is more important if filming in a windy place or by hand rather than from a tripod. Again ‘optical’ is mechanical stabilisation of the image and ‘digital’ is done by cropping the image a little and compensating for your movement; optical stabilisation is again better.

Battery

Most cameras come with a small battery relative to those available. If you are going to be filming all day you’ll need a few batteries, so it’s worth checking the cost of spare batteries before you buy a camera. All manufactures make bigger versions of the default battery but there are also second party ones. Often good second party batteries are cheaper and work as well as the manufacturer's, but they sometimes lack Dolby chips, which allow the camera to know how much battery it has. Lacking a Dolby chip can be a pain for two reasons: 1) when you turn on the camera or start recording the camera may claim it can’t talk to the battery and ask if you want to continue (this may stop recording) and 2) you don’t know when the battery is going to die. Issue 1 isn’t a problem if you're not concerned about getting the camera working at the drop of a hat. I set up the cameras on tripods and had them record for hour intervals so it wasn’t an issue that they needed confirmations before they began filming. However, if you are sitting and waiting for an animal to do some momentary action that you need on film this delay could be a problem. Issue 2 is a bit more annoying but if you test how long the camera lasts when filming on the battery and keep track of how long it’s been filming (allowing some room for error) you'll probably be ok.

Words like ‘better’ and ‘worse’ are, of course, relative terms and the less good option may still be good enough depending on what you are doing. For example progressive scanning is better for filming fast moving objects but, depending on what you want to see, interlaced scanning may still be good enough. Similarly you may find that while filming in a high quality format gets a better image you may find lower quality footage is still good enough to make out what you need to see to do your research. On that note I advise where possible doing test runs to check what formats and specs are ok. This could be done on a model similar to those you want to buy (perhaps borrow from a friend or colleague).

I hope that the above has helped you work out what you may need and understand what these different specs mean. As I already said, what you need depends on what you are doing. You’ll have to decide what is good enough. However, I will say that I was able to quite adequately film and identify bees from tripods set up a meter away from fireweed plants filming in a 1920x1080p format, as long as there wasn't a lot of disturbance from the wind. Unless you’re filming something very small from very far away such a format should probably do quite well.

By Michael Harrap

Michael is an MRes student who studies pollinator foraging behaviours within vertically arranged inflorescences.

If you are a scientist and not already on twitter, I urge you to join! You might be reluctant to join (another) social media website, but the benefits of twitter are too good to miss out on... 

What is twitter?
Twitter is an online social media website, which allows users to send and read short messages (of 140 characters) called “tweets”.  

Six reasons why you should be on twitter:

1.       Communication

Twitter is a great tool for academics to communicate about their research to other academics and to the public, to announce and share publications, and to write and debate about relevant research issues (in an unrestricted manner). Furthermore, scientists are using social media to circulate information about potential opportunities in their lab, upcoming events, or to post updates from meetings and conferences. Along with forging links between scientists, interactions on twitter can improve communication between scientists and the general public.

If you are shy or hesitant, twitter is a great forum to ask a question, voice your opinion, or to start up conversations with leaders (or anyone) in the field, a common problem for early stage researchers! Unlike a conference setting, twitter allows you to sit back and read a conversation between other scientists (without awkwardly standing there), and gives you plenty of time to think about a comment or response (if you feel like giving one).

2.       Networking and exchanging ideas

Twitter is a tool for engaging and communicating with a massive global network of peers and researchers across the world. Twitter allows scientists at any stage of their career path to connect with other scientists, removing the barrier of status. You are able to connect with people who have similar (or very different yet fascinating) interests. Twitter, unlike other social media websites, allows for real time conversations to happen, so you can get direct input and feedback from other academics and the general public. It is a great equaliser and allows for easy communication with people whom you might not ever interact with otherwise.

Are you attending a conference? Twitter can connect you with people who share similar interests to you before you even get there. If you cannot make the conference, following a conference hashtag (e.g. #ESA2014) can keep you informed with what’s happening, who presented, what people thought, what was particularly interesting etc.

3.       Dissemination

Twitter allows you to get your message out there, and the potential platform is immense: compare an audience at a conference with the potential online audience of twitter. For instance, 1731 tweets by 176 people during the 2011 International Congress for Conservation Biology reached 110,000 Twitter users. Not bad! More info here.

Scientists want other people to read about their research right? Studies have shown that tweets linking to peer reviewed PDFs are retweeted 19% of the time, exponentially increasing dissemination. 

Click here for tips on how to use twitter and blogging to disseminate your research.

4.       Inspiration, innovation, exploration

Twitter can be used to keep up to date with the most recent published articles (you can follow journals directly) and is a great resource for scientific inspiration (e.g IFLScience). It is exciting to read other people being enthusiastic about their work, debating with others and communicating with experts in other fields about research that’s happening as we speak. I follow a lot of field biologists and natural historians (e.g. @SeymourDaily) who will often post photos from the field (@Primate and predator) which keeps me excited about nature.

Are you a biologist with a secret passion for astronomy? Twitter allows you to follow whoever you like. You can follow astronomers, NASA, explore hashtags relating to astronomy… giving you access to current and exciting research you might never have learnt about otherwise.

5.       Opportunities

Twitter allows you to enhance your online visibility, it can be very useful to have an online presence these days, especially as an early stage researcher. Who knows, maybe this “getting noticed” could help in the highly competitive job market.

Following a lab group or researcher that you are interested in working with can be a good way to stay up to date on their research, and learn about opportunities in their lab as they come up, all improving your likelihood of getting job. Following that, there are various useful twitter feeds, such as conservation careers (@conservcareers) that post job opportunities on a daily basis.

6.       Helpful resources for grad students

There are loads of specialised groups that are aimed at grad students helping other grad students (#phdchat). For example: tweets by the thesis whisperer team (@thesiswhisperer) offer advice and useful tips on writing and other PhD related stuff. If you are having problems with statistics, there are lots of specialist groups such as R-package related hashtags #rstats, or you could also follow @Rbloggers and statistics for biologists @statsforbios to name a few.