Bats and Infrared Cameras

Night vision or infrared lighting and Canon XA30 camcorder

After making the decision to invest in infrared camcorders two years ago they have come into their own this year with changes to how site surveys have been carried out especially with social distancing. Infrared camcorders such as the Canon XA30 and Sony AX100 and AX700 with the assistance of artificial infrared lighting can record in complete darkness and with the AX700 you can record HD at 120 frames per second which for bats is extremely useful as they emerge at speed from the roost point and a split second to look at your notes or detector and bang you missed the bat emerge whereas the camera doesnt blink and can record in complete darkness as if in daylight. The lights are powered by 12V DC portable battery usually used for charging mobile phones or as backup to power a router.

These camcorders have been used to do roost counts on emegence surveys and on swarming surveys at dawn, the ability to see through the darkness means that bats dont get missed and each individual bat can be counted in and counted out, the BCT guidance from 2016 doesnt really detail the use of camcorders and is critical of the limited field of view but this simply isnt the case with a 28mm lens which is wider than our own field of view; where you have species such as brown long eared bats which are often silent when emerging from a roost or when light sampling inside a barn, the use of infrared filming can be used to identify bats without disturbing them as the infrared lights do not impact on bats unlike conventional torches or those fitted with red filters. Hopefully the guidance gets updated to reflect the use of these camcorders in the same way thermal imaging was looked at.

The camcorders are also useful to locate the exact roost point for example by recording bats emerging from tiles high up on a roof which at night is often extremely difficult especially if not backlit and having a pictorial record ofthe bats emerging or re-entering a roost provides certainty of accuracy of surveys without needless repeat surveys because the exact roost point hasnt been detected on site surveys.

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