During a flight, both the shooter and thermal operator sat on the floor and were tethered to the helicopter using approved aviation quick-release harnesses (Fig. 2). The tether was as short as possible, yet long enough to allow the crew member to lean over to see the ground beneath the helicopter. We set the thermal imager to output ‘white-hot’ greyscale imagery, which was the operators preferred output.
The aircraft (AS350 B3 Écureuil [Squirrel] helicopter; Aérospatiale, France) was positioned at approximately 50–100 m above ground level and flew at 15–25 knots ground speed. The helicopter searched the area using a pseudo-systematic search pattern: the area was flown in parallel transects allowing for thorough coverage and the helicopter deviated from the search pattern to pursue target animals. When a potential target was detected, the thermal operator verbally alerted the shooter and pilot, providing information on the suspected species and its general direction/location. The thermal operator also identified the target’s location to the shooter and pilot by switching on a 12 V, 1 W, 520 nm focusable laser pointer (Oxlasers, Shanghai, China) (Fig. 3). The shooter carried handheld thermal binoculars and used these to confirm the location and species of the detection. Where detections were obscured by vegetation (i.e., something warm was detected but identification could not be determined), the pilot would reposition the helicopter, generating rotor wash to flush the animal so it could be identified. During these programs the shooter used a Springfield M1A .308—calibre self-loading rifle with 135 grain hollow-point ammunition for pigs, and 150-grain soft-point ammunition for deer. Incapacitation of animals had to be confirmed by both the shooter and the thermal operator and was based on cessation of movement and wound placement.