Data cleaning and statistical analysis
We downloaded the footage from the thermal imagers to an external hard
drive and reviewed the footage from this drive using VLC media player
3.0.8. We recorded observations in a custom-built Microsoft Excel
(Microsoft Corporation 2018) workbook which utilised the drone’s
tracklog to georeference observation locations. This file was then
exported as a KML file and viewed in Google Earth Pro (Google Earth Pro
2019) to aid in comparison between thermal imager and visual inspection
detections.
Where transect imagery overlapped, double observations of warren
entrances were removed. If a warren complex was identified on one
transect, and additional warren entrances were identified on the
immediate next transect in the same location, then a determination was
made on whether these entrances belonged to the same warren or
constituted a new warren. This ensured warren counts were not
over-estimated.
Warrens were classified by the amount of vegetation present that was
likely to obscure entrances. Warrens with no vegetation present were
classified as “open”, warrens obscured by vegetation (e.g. entrances
were beneath shrubs) were classified as “vegetated” and warrens that
had entrances in the open and obscured by vegetation were classified as
“mixed”. These classifications also applied to the entrances
associated with that warren for analysis (i.e. individual entrances in
“mixed” warrens were not further classified into “open” or
“vegetated” categories for analysis).