Saturday, 21 January 2012

Navigate that bat!

This is an exciting time for bat survey technology: after a number of years of stagnation the equioment available for surveying bats is taking some serious leaps forward. A number of new pieces of equipment have appeared on the market over the past 18 months and several more will be available soon. But sometimes it's not the equipment that matters so much as how you use it.

I have been using Anabats extensively for a number of years, both for passive monitoring (automatic recording of bats in flight) and for transect surveys(walking or driving a survey route, recording bat activity). The Anabat's ability to be connected to a GPS unit to record grid reference data alongside recorded bat passes is especially useful in understanding bat activity as you can plot the location of each bat pass accurately on a map. However, this tends to take a bit of post-survey work (unless you use a personal computer with your Anabat/GPS combination...but madness lies that way if you're not an uber-geek).

The flexibility and potential of Anabats for generating extensive high quality data has led them to move out of the realm of the professional bat ecologist and into the hands of voluntary bat groups around the UK. They're not cheap at around £1400 each, but many enterprising bat groups have obtained funding and are using their Anabats to great effect, generating lots of new biological records of bats.

A Bat-Nav in place on an Anabat SD1. In practice I found that the magnet wasn't sufficiently powerful to hold it in place (photo copyright Wildwood Ecology)

Recently I came across a new gadget, designed to be used in conjunction with an Anabat. In essence Wildwood Ecology's Bat-Nav acts as a GPS plugged into your Anabat and feeds it grid references as you walk or drive around. It comes with a simple but effective computer Widget, which uses Excel to extract your bat records and GPS file and generate a KML file. This file allows you to see your bat records plotted on Google Earth with a miniumum of fuss.

The Bat-Nav is designed to be used with an Anabat SD2 and draws its power supply from the USB socket on the machine. As I only had an older SD1 available for testing Wildwood kindly rigged up a wire to connect to the positive side of the battery pack, which worked ok. Since then Wildwood have launched a model designed to be used with an SD1.

To test the Bat-Nav in practice I used it to do a car-based survey around my home village one night in September. Wildwood suggest the unit can be attached by it's own magnet to the Anabat's own steel casing. I found the magnet too weak for that, but it stuck to the car door very well.

I recorded plenty of bats during a 2 hour drive. When I got home I used AnalookW to identify and label each bat call and created a count labels file in the usual way (if you've never used AnalookW, it is a delightfully easy to use piece of software for identifying bat calls which, with a few clicks allows you to create a simple spreadsheet). I then opened the data in the BatNav KML generator (see above) and after half a dozen clicks I had a KML file. All I had to do was click on the file for it to open in Google Earth (you probably have to have Google Earth already installed) and here is the result.

The transect route is shown as a yellow line, with each bat pass labelled (I chose to label P5 for Soprano Pipistrelle, P4 for Common Pipistrelle, Psp for unidentified Pipistrelle and Msp for Myotis). For anyone with access to GIS software (and the training to use it) this kind of thing is easily prepared, though it takes a little time. If you don't have acces to GIS or want a quick and simple way of looking at your bat data geospacially, this fits the bill. You can also manipulate the data three-dimensionally in Google earth and even look at it in Google Streetview, as you can see below.

Would I buy one? I think I would, though it's not without drawbacks. The area I chose for my test survey is in open farmland and the terrain is clear to see from the air. A woodland transect would be far less clear, with the tree canopy tending to hide paths and some roads and structures. Sadly Google Earth does not (so far as I know) allow you to convert between the satellite view and a decent map view (for that you need, which allows you to use Ordnance Survey maps as well as satellite images. Unfortunately it's part of Microsoft's evil empire, but these are the breaks).

Another niggle is that the magnet is disappointingly feeble, making it less usable for walked transects, but some sticky-backed velcro would probably sort that out.

Of course £150 is rather a lot of cash to shell out, especially if you already have a GPS receiver you could use. A friend of mine said it just took him a couple of hours, playing with Excel and Google Earth, to work out how to produce his own KML files. But he's a bit of a geek (sorry Tom). Perhaps Wildwood should consider selling the KML generator widget separately from the magnetic GPS - they may find some customers who are already happily using a normal GPS with their Anabat, but would like the hassle-free conversion to KML.

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Send me your thoughts/comments - email David Dodds