Surveying for bats is notoriously difficult. Especially roost emergence surveys, as seeing bats emerging from buildings or trees after dark is almost impossible unless the lighting is 'just right' and emerging bats may be seen in silhouette. Using a torch, even one with a red filter over it may affect the emergence of bats from a roost. If the roost is under the eaves there may never be enough light to see exactly where bats emerge from and to be able to count them properly - did the bat come from the eaves or did it fly over the roof? Even using night vision goggles means that the observer has to maintain absolute concentration and focus for up to two hours - blink and you'll miss it.
The problems of studying bats emerging from, or returning to roosts, after dark are:
Being unable to see where the bats emerge from or return to.
Maintaining vigilance to record all animals that emerge or re-enter.
Being unable to accurately record numbers as you could miss some as you write down what you have just seen.
The BATCAM system provide accurate data and verifyable evidence of emergence and numbers. The equipment can be set up to cover suspected areas with entry points or pointed at known locations. Once the static monitoring points are set up it allows the recorders the ability of walk around the site to check if different exit points are being used and record these, or move/ add equipment to cover these locations.
An economical system can be put together that will make recordings at a site to document all emergences or re-entries. Add to this the ability to record ultrasounds and a full monitoring station can be set up. Typically emergence surveys are done for 2 hours. At dusk it is from sunset plus 2 hours and at dawn it is from 2 hours before sunrise until sunrise.
Using several of these setups negates the need for using multiple surveyors at expense to the client. The relatively little extra time taken to analyse the video and audio footage is soon recouped as more stations of observation are added to the survey (typically 4-6 observers may need to be used for building complexes). Using multiple obervers still does not remove some of the missed bats and the uncertainties.
The result is positive records of emergences and re-entries, time indexed and with audio that can be used to confirm the identification of the species. These are analysed using video editing software where the ultrasound recording can be synchronised with the video footage to hear the echolocation sound and see the event. This is useful if the bat is detected on the recorder as it can shortcut some of the time spent skipping through the video footage. Look for the ultrasound spikes and you may see and emergence (or it could just be a bat flying behind the camera that is picked up by the recorder). Conversely quiet bats may not be loud enough to show spikes on the audio timeline, which is why the viedeo needs to be watched in its entirity to make sure all bats are 'seen'. Heard may be a bonus.
The setup shown here uses a BATBOX Baton and a digital music recorder and records continuously for the duration of the survey. Overlaying this onto the video is one way of indexing emergences. Alternatively (as suggested by Stephanie Cooling at the 2016 National BCT bat conference) a different type of detector can be used that creates a small file each time the device is triggered by a call. These files are time stamped and can be cross-matched to the visual events on the video timeline.
Below is the typical setup with the IR camcorder on the left. The digital recorder is next, to the right, and the ultrasound bat detector to the right, linked via the red lead. To the right are two powerful IR torches. Both the camcorder and the torches are zoomable and can be set either to take an overview of a scene, for example where there is a need to explore if bats are emerging from a roofline or part of a tree or can be zoomed in onto a known emergence point.
The whole set is mounted onto a tripod and can be aimed at the scene to be monitored and the torches are independently positionable to illuminate the scene adequately. However, the tripod mount point can be replaced with a pistol grip and the whole bar then becomes a freehand setup that can be used to walk around the site and record anything in the process.
This is the system we have developed that works for us, but we welcome inputs from others on their experiences. Please contact us if you would like to be involved in developing IR systems. The current summary of the system can be dowloaded from HERE.
DRYAD ECOLOGY can source the equipment and provide training in its use. We can also do surveys for you using this equipment and analyse the data. If you prefer, we can also analyse your data at econimical rates. Please contact us for more information.