Collar attachment and logger deployment

Some of the trapped badgers were equipped with a GPS collar. The decision as to whether a certain individual was chosen to have a collar was dependent on whether they tested DPP test-negative in the field (in 2015–2017), whether they were adults weighing more than 8 kg, and whether they had a head diameter 1 cm larger than their neck diameter (to ensure the collar could not easily slip off when they were released)⁵⁸. In the event, when badgers were captured for the purposes of deploying DD loggers, all individuals were heavier than 8 kg. Therefore, it was not the case that certain individuals were excluded from having a DD tag (e.g., those with poorer body condition). We attempted to equip one male and one female with a collar containing a DD from each social group. Collars had a DD logger affixed using two crossed cable ties (30 cm long, 4.8 mm wide) and Tesa® tape (No. 4651; tesa AG, Hamburg, Germany)⁵⁶. DD loggers were encapsulated within 3D printed styrene plastic cases, each with a 3.6 V battery (1/2 AA 3.6 V 1200 mAh Lithium Thionyl Chloride, Saft, Levallois-Perret, France), which was secured to the collar that contained the GPS (Tellus Light, Followit, Sweden) (total weight c. 270 g). Daily Diary loggers were attached to the subject such that the X-axis corresponded to the ‘surge’ motion (front-back acceleration), the Z-axis with ‘sway’ (left–right acceleration) and the Y-axis with ‘heave’ (up-down acceleration)⁴⁶. Device magnetometers were calibrated by rotating them through 360° to correct for magnetic hard and soft iron distortion⁵⁹. The GPS units recorded position fixes until the battery power was spent (up to 273 days post-trapping) and were programmed to record a locational fix once per hour between 21:00 and 04:00^47,52, which corresponded to the period when badgers were likely to be most active⁴⁵. Collars transmitted between one and eight fixes per night, dependent on GPS signal availability (for example, fixes were unlikely to be transmitted when badgers were underground⁶⁰). Collars were positioned so that the accelerometer casing was on the side of the neck, the GPS battery on the bottom and the GPS receiver on the top.