The new generation of unattended bat detectors

It's been a little while since I wrote a blog post, which has irritated me as I have a host of subjects I want to write about, but so little time to do it. However, the inevitable bat worker calendar effect has happened and I am looking out of the window at deep snow and reflecting on the fact that my "to do" list is the shortest it has been for about a year. This wonderful situation won't last long so I'd better get blogging!

Back in 2011 I wrote about the rivalry between Titley Electronics and Wildlife Acoustics, whose Anabat SD1/2 and Songmeter SM2BAT were at that time the only realistic options for unattended monitoring of bat calls. Both machines had strengths and weaknesses, both were (and still are) very widely used by ecologists and bat researchers.

In the past year both companies have launched new unattended bat detectors. In both cases they seem to have listened to customers in an effort to improve on their previous models. It is interesting that the result of their market research has been very different. Wildlife Acoustics moved up-market with a signficantly more expensive machine, the SM3BAT and Titley went for a smaller and cheaper machine, the Anabat Express. I am fortunate enough to have had my hands on both machines for the past year and have had an opportunity to put them through their paces.

Wildlife Acoustics' Songmeter SM2BAT and the slightly improved SM2BAT+ have achieved much popularity in the UK and elsewhere in recent years. Their price tag of around a thousand pounds made them cheaper than the Anabat SD2, though still expensive for non-commercial users. Their ability to record from two microphones at once was attractive, especially for those wanting to record at height and at ground level simultaneously and the fact that they recorded to SD cards, rather than the dated CF cards used by Anabats was also attractive. However they were complex to use, requiring careful setting up and were easy for the inexperienced user to get wrong.

Perhaps Songmeter's most attractive feature compared to the Anabat was that they came in a waterproof case, whereas Anabats needed an additional weatherproof box - Pelicases for the well-heeled, sandwich boxes for others! The  Songmeter's big selling point was that it arrived oven-ready, without the need to fabricate a waterproofing solution. However they suffered from condensation at times and the internal memory card holders were vulnerable to damage when inserting the massive D cells the machines use. Exposing the internal workings of the machine to change batteries or memory cards in inclement weather was hardly ideal, though the SM2BAT+ model had it's internals sprayed with a water-repelling coating to improve this.

Anabat SD1 and SD2 models need additional waterproofing for unattended use. This sandwich box is the low-tech approach!

An SM2BAT mounted at the base of a mast, with one microphone attached and another at the top of the mast, connected by a cable.

Unlike Songmeters, Anabats (this is an SD1) can also be used for transect work.

The Anabat SD2 (and the previous SD1 model) by comparison, though about 35% more expensive was more robustly built (waterproofing aside) and much easier to use, reducing the risk of expensive repeat surveys. They also use standard AA cells, rather than the larger D cells used by Songmeters (though both can also be connected to external 12v batteries for longer term use). They also have the advantage of being excellent for hand-held transect surveys, whereas the Songmeter can only be used passively.

So given all these pro's and cons I was intrigued to see what the two new machines are like and how the two manufacturers have responded to the feedback of their customers.

The Songmeter SM3BAT was the first of the new machines to reach me. One of the criticisms of its predecessors was that they were a bit "plasticky" and some parts were easy to damage. My first impression of the SM3BAT was that it had been cast in a furnace, rather than built! It's taller than the old machine and the case appears to be capable of withstanding having cattle tap-dance on it (a more common issue with this type of equipment than you might think), though I wouldn't recommend experimenting with that. It's also heavy at 2.5Kg without batteries. The solid metal casing includes holes for securing the machine, either by bolting it to a wall or by attaching it to something solid with a bicycle-lock style cable.

The SM3BAT in use. The microphone is at the end of the cable on the right, allowing the machine to be put out of sight if necessary.

The controls and screen are now on the outside of the machine, with robust plastic to protect them. Battery compartments and memory card compartments are accessed by removing waterproof plugs on the side, so that there is no longer any reason (or indeed any ability) to access the interior of the case. Thus several criticisms of the SM2BAT are removed - the new machine feels solid and robust, it gives confidence that it can cope with whatever is flung at it.

In use the SM3BAT is similar to the SM2BAT. It can record in ZCA (Analook) format, or in WAC or WAV formats. As before there are four memory card slots to allow you to provide the machine with plenty of space for the latter two memory-hungry modes. Wildlife Acoustics are proud of the fact that it is compatible with the latest generation of 256GB SD cards, providing potentially a Terrabyte of memory. A big criticism of the SM2BAT was the memory-hungry nature of Wildlife Acoustics' preferred WAC format. With advances in computer technology the ability to store and process large amounts of data has become steadily easier since then, though that burden should still not be underestimated if you plan to use these modes.

The SM3BAT comes with an upgraded microphone, which like the SM2BAT one is omnidirectional (a key difference to the Anabat SD1/2 microphones, which are unidirectional). However it is significantly bigger and can no longer be plugged directly into the side of the casing. Wildlife Acoustics advise it is more sensitive than their previous microphone.

Titley Electronics' new machine is the Anabat Express. They have chosen to produce something much more compact and with less visual impact than their competitors machine. The Express is a similar size to the old Anabat SD1/2 but is now in a camouflaged waterproof case. The case, though made of plastic is strongly made and similar to those used for camera traps. It now has an omnidirectional microphone, which is stored safely in a slot within the case and then screwed into the exterior for use. Unlike the SM3BAT the Express has a built-in GPS, which it uses to calculate sunset times (the Songmeters need to be programmed with their location to calculate this). This is a big step forward for Anabat. Titley's previous models could only be programmed to start and end recordings at fixed times, with no allowance for day-by-day changes in sunset and dawn times. Songmeters have the useful facility to start and finish at a set time in relation to sunset or dawn. Now the Express can do this, with the added bonus that it doesn't need to have latitude and longitude pre-programmed, as with Songmeters.

The diminutive Anabat Express, with a £2 coin for comparison.

The interior of the Anabat Express, including built-in instructions.

In use the Express is virtually idiot-proof (believe me, I'm an excellent measure of this). When we're out in the field, setting up equipment and it's cold or wet and we've been working all day even the best ecologist or bat-worker is liable to do something daft - we're only human after all! The Express even has step-by-step instructions pasted to the inside of the lid. All you have to do is connect the microphone to the outside, switch it on and wait for the GPS to get a signal. Then you cycle through three options for recording time (continuous, sunset to dawn or pre-programmed), close the case and you're ready for action. A cord attached to the case ends in a magnet, which can be used to check the machine is functioning correctly. A friendly blue light winks to confirm all is well when the magnet is placed in the right position on the case.

The Express uses standard SD cards, with no prior set-up, so formatting CF cards is a thing of the past. Of course, unlike the Anabat SD1/SD2 this machine isn't suitable for transect or other hand-held work - it's only effective as an unattended detector. It only records in ZCA format, so if you prefer to use audio recordings for analysis this is something to think about. Personally I prefer ZCA for most purposes. I'm not thrilled about the fact that you have to open it up to operate it - that was one of my criticisms of the Songmeter SM2BAT. However, the interior of this machine is far more robust than the SM2BAT and, like the SM2BAT+ the interior has been sprayed with a water-repelling coating.

So Titley have chosen to go for a low-profile, simple-to-use machine, whereas Wildlife Acoustics have gone for a big, solid, bomb-proof detector. Which would I buy? As ever it's a case of horses for courses. The SM3BAT suffers from high visibility but balances it by being massively robust. It would be hard to install it in a situation where theft or vandalism is a concern. Not only is it big and obvious it looks expensive. Your average thieving ned couldn't help but wonder what it will fetch on eBay. Although it can be securely attached to something, that wouldn't protect the controls or the battery and SD card compartments from interference. At over 2.5Kg before you put batteries in, you wouldn't want to carry a rucksack of these machines around a site for temporary installation. However you might choose it as the ideal machine for long-term installation on a met mast, or somewhere where unauthorised interference can be prevented.

The Anabat Express on the other hand doesn't suffer from these security issues. It's small and camouflaged and therefore suitable for installation with low visual impact, perhaps in places with regular visitors. It comes in a protective zip-up case and you could happily carry a dozen of them with you all day. So for short-term, high risk installation it couldn't be better and I like many others already have several of them for that purpose. If you do want to install one in a higher-risk situation Titley sell a steel case and steel python cable, allowing you to attach it securely to something solid. The Express is also very easy to set up in the field, so the risk of mistakes is low. Unlike the older Anabats you don't need to worry about where the microphone is pointing and it lends itself to attachment to a tree trunk or similar.

An Anabat Express in use with Titley's optional security system

There are a couple of other issues to consider in comparing the two machines. One is power consumption, Wildlife Acoustics claim that the SM3BAT is less power-hungry than the SM2 models were and claim up to 20 nights on a set of four Alkaline D cells. It can also be used with an external 12 volt battery or power supply. The Express can last for up to 30 nights if you use Lithium AA batteries (high capacity Lithium batteries are not an option for D cells, so far as I know). you cannot connect an external 12v battery to the Express, so it's not a machine for long-term use, though 30 nights is a long monitoring period!

The other thing to consider is price. Wildlife Acoustics have abandoned their £1000 price point with the SM3BAT, which sells for over £1400. This compares with £660 for the Anabat Express. In other words you can have two Expresses for the cost of an SM3BAT and still have money left over. I supsect this is the clincher. Both are good machines, both appear to work extremely well and I have had no problems with reliability of either machine. But two machines for the price of one is hard to ignore, especially when the Express is also less likely to be stolen or vandalised and easier to deploy in numbers across a site. For bat groups and those working on a budget the decision seems like a no-brainer. But if you want a long-term installation or if you want something with a well-engineered and professional appearance perhaps the SM3BAT has something to offer.

It's particularly interesting that Wildlife Acoustics have now launched a smaller, lower-cost, ZCA mode only model called the SMZC. From the little I have seen it seems extraordinarily like an attempt to emulate the Anabat Express, though it still has the look of something made in a foundry and weighs 1Kg (the Express weighs 385g). It also lacks the GPS functionality of the Express, but is priced about 10% cheaper, so it may turn out to have something to offer.

Please note that all prices quoted include VAT and appear to be correct at the time of writing. All weights exclude batteries. 

See our website: David Dodds Associates Ltd

Anabats and Songmeters

I have written before about my good opinion of the Anabat SD1 (now replaced by the SD2, with some minor upgrades), a machine which offered huge advances in passive monitoring of bats (i.e. leaving a machine on site to continuously record bat calls), in use with a GPS receiver for walked and car transects (where a route is followed, recording bat calls and their locations) and for use as a training aid when connected to a PDA personal computer, to display live sonograms of bat calls. Prior to the arrival of the Anabat the only way of doing these surveys was with a Frequency Division bat detector, recording WAV (or poorer MP3) audio files: a massively time-consuming and data intensive process, so the Anabat was a big step forward.

Like all good things, the Anabat had some downsides: reliability has never been as good as it might be, technical support is patchy and confusing and the price (around £1400) is prohibitive for many users. So the arrival of the rival Songmeter SM2 on the UK market last year generated a lot of interest. At around £800 it is clearly cheaper and many bat workers and ecologists were excited to try out the latest generation of bat detector. Personally, I was quite cynical and, having had the chance to use several Songmeters this year, my reservations may have been justified. Let me clear though: I am not saying that the SM2 is not a good piece of equipment: it has a lot going for it. What I am saying is that, just like the Anabat, it has strengths and weaknesses and to claim as some have, that it is a technical advance on the Anabat is simply nonsense!

The two importers of the Songmeter, Alana Ecology and Envisage Wildcare have marketed the Songmeter powerfully in the U.K. and it's arrival on the market suggested that it was a new and exciting development. In fact the Songmeter had been on the market in the U.S., alongside the Anabat for quite some time. Anabat had been successfully sold in the U.K. by both companies for several years and both provided excellent technical support. In early 2010 Titley Electronics (who make the Anabat) suddenly withdrew the product from them and set up a European sales office in the U.K. Deprived of a key part of their product ranges, both companies looked around for a replacement product and settled on the Songmeter. So it's arrival here was a result of commercial necessity, rather than technical development and the flurry of interest in it is primarily a result of marketing hype. So I was interested to get my hands on some Songmeters this year and find out how they match up to the hype.

An Anabat SD1. The later SD2 version has a USB socket on the right-hand side, rather than a serial port. The velcro on the left was stuck on to allow a GPS receiver to be attached for transect work.

A key advantage of the Anabat is the fact that it converts bat call audio to a digital format, so that each bat pass generates a tiny file of around 2-5KB. Thus a 2GB memory card can last weeks or even months, without needing to be replaced. The SM2 records WAV high quality audio, compressed to form WAC files. Theoretically, this allows the creation of better quality sonograms for analysis. Unfortunately, the compression results in very large files, compared to Anabat. My experience of using SM2 has been of long hours spent downloading, copying and converting many tens of Gigabytes of data. The Songscope software supplied by Wildlife Acoustics (the makers of Songmeter) is expensive and unpopular, so that most people use Analook (the Anabat software) to analyse Songmeter data. Wildlife Acoustics supply a free program (WAC2WAV) which converts WAC files to ZCA format, so they can be analysed using Analook. However, running WAC2WAV on large amounts of data (and most passive monitoring produces large amounts of data) is slow and tiresome.

Using Anabats for passive monitoring has always created the problem of waterproofing, leading to many imaginative ways of keeping Anabats dry and free from condensation when used in the field. Unfortunately, long-term use in our wet Scottish climate has always been a problem, with inevitable condensation build-up leading to failure if the machines aren't occasionally taken somwhere warm, to dry out for a few days. The SM2 case is waterproof in itself and needs no further protection. It also addresses the Anabat problems by including "Humisorb" pouches inside the units and having a valve to equalise air pressure inside with that outside. That sounds ideal and would be...if it worked. At present several of the SM2s I am using have proved unequal to the challenge of a cold, wet upland site, with quantities of condensation present inside the machines. In fairness, none has yet stopped working and the manufacturers have proved keen to find a solution. Only time will tell if they are successful.

There is a clear cost benefit in buying an SM2, rather than an Anabat, but there are also hidden costs. A 2GB CF card for an Anabat costs around £15, but a set of four 32GB SD cards for an SM2 could set you back several hundred pounds (how many you need will depend on how often you download data). SM2s have internal capacity for a set of outdated D size batteries. The machines reportedly do not respond well to the lower voltage produced by rechargeable batteries. Happily the machine, like the Anabat, will work with an external Sealed Lead Acid Battery. Unlike the Anabat, you will have to pay around £100 for an external voltage regualator. Oh, and if you want the software designed to be used with the Songmeter, that will be another £500.

Probably my biggest beef with Songmeter is its lack of flexibility. It is a passive monitoring machine. Full stop. Anabat has a range of potential uses, as I described above. The SM2 does have some interesting potential though. For example, it comes with an in-built temperature recording unit. It also has the ability to work with two separate microphones concurrently. Potentially, this allows some interesting studies to be carried out, using extension microphone cables. For example, recording the direction of bat movement along a linear feature such as a hedgerow or comparative studies of bat activity at ground level and at height.

A Songmeter SM2 in position, attached to a post. This unit is being operated with two microphones simultaneously.

Another intersting feature of the Songmeter is it's omnidirectional microphones, which pick up bats in all directions. This is potentially a useful feature in a passive monitoring machine. When a detector is used in the hand we tend to point it at bats we hear, getting the clearest possible calls. When a detector is used passively the directionality of the microphone works against us, so an omnidirectional microphone seems a good idea. However, it has drawbacks too. A microphone which picks up bat calls in all directions also picks up background noise from all directions too, reducing the gap between noise and bat calls. This could easily reduce the clarity of a recording and increase the number of non-bat ultrasound recordings.

My biggest beef with the Anabat has always been it's limited ability to keep accurate time. Over a period of weeks they are fine, but over protracted periods of use the internal clocks tend to lose or gain time. So far the SM2s I have been using have been reliable in that respect. They also have a useful ability to be set to start and stop recording at specified periods before sunset/after dawn, rather than specified start/finish times, as with the Anabat. This saves having to reprogram them through the year, to reflect changing dawn and sunset times.

One colleague I spoke to this year was hopeful that using SM2s intead of Anabats might reduce the number of equipment failures. Sadly that hasn't been my experience. It's easy to think that, when you buy a machine with a high price tag you are getting high quality electronics, but electronic development doesn't really work that way. The major cost in producing any electronic equipment is the initial development cost. If you are developing a new iPod, confidently expecting to sell millions of units, you can afford to invest millions of pounds in perfecting the design. If you are developing a bat detector, with an expected sale of a few thousand units then the development budget is inevitably much smaller. In this respect both machines are in the same boat and they appear to have an equal propensity to fail.

So what would I spend my cash on? Well, the SM2 is an interesting piece of equipment, with some useful features. It had the potential to knock the Anabat for six on waterproofing and reliability, but so far it has proved no better on either score. It lacks the Anabat's flexibility and it's memory-hungry format is time-consuming to manage. So, unless I was involved in a project which could benefit from the specific extra capabilities of the Songmeter I would spend my hard-earned cash on an Anabat.

Wildlife Acoustics (maker of the Songmeter) www.wildlifeacoustics.com

Titley Electronics (maker of the Anabat)

www.titley-scientific.com

Wildcare & Alana (the UK Songmeter importers) http://www.wildcareshop.com
http://www.alanaecology.com


My website: www.plecotus.co.uk