Improving Terrestrial Squamate Surveys with Camera-Trap Programming and Hardware Modifications

SIMPLE SUMMARY: Camera-traps are a useful tool in wildlife research and management, as they allow researchers to observe wildlife with minimal intrusion. However, despite their utility, the rapid pace of technological change and the relative novelty of camera-traps in wildlife research mean that many aspects of their use have not been resolved. Put simply, it may be possible to use camera-traps far more effectively than they are currently being used. Here, we examined whether detections of terrestrial snakes and lizards could be improved with camera-traps by using both time-lapse and passive infrared triggers, which are present on most camera-traps, and by adjusting the focal length of the camera to improve image clarity. Additionally, we examined whether increasing the sensitivity of passive infrared sensors is of benefit. We found that using both types of trigger simultaneously improves detections of terrestrial snakes and lizards, and users can modify the focal length to improve image clarity of fauna that occur close to the lens. These minor adjustments in the use of camera-traps result in major improvements for detecting terrestrial snakes and lizards. ABSTRACT: Camera-traps are used widely around the world to census a range of vertebrate fauna, particularly mammals but also other groups including birds, as well as snakes and lizards (squamates). In an attempt to improve the reliability of camera-traps for censusing squamates, we examined whether programming options involving time lapse capture of images increased detections. This was compared to detections by camera-traps set to trigger by the standard passive infrared sensor setting (PIR), and camera-traps set to take images using time lapse in combination with PIR. We also examined the effect of camera trap focal length on the ability to tell different species of small squamate apart. In a series of side-by-side field comparisons, camera-traps programmed to take images at standard intervals, as well as through routine triggering of the PIR, captured more images of squamates than camera-traps using the PIR sensor setting alone or time lapse alone. Similarly, camera traps with their lens focal length set at closer distances improved our ability to discriminate species of small squamates. With these minor alterations to camera-trap programming and hardware, the quantity and quality of squamate detections was markedly better. These gains provide a platform for exploring other aspects of camera-trapping for squamates that might to lead to even greater survey advances, bridging the gap in knowledge of this otherwise poorly known faunal group.