2.2.3 Camera trap surveys
A pilot study was conducted from May to July 2017 to fine-tune the camera trap data collection method. Twenty four static camera traps were deployed based on field rangers’ perception of areas where bushpigs could be found. During the pilot study, the duration of each camera trap placement was variable because NGR has a history of extensive theft of cameras by poachers. Camera traps were removed immediately after signs of human activity were observed near a camera. After the pilot study, 48 camera trap stations were randomly positioned within the four main vegetation types (Fig 1). Camera trap surveys were conducted from February to December 2018. At each camera trap station, a single camera was tied to a tree or stump at bushpig height (30-50 cm above the ground) or higher (150-200 cm) with a downward pointing inclination, depending on the vegetation. Surrounding vegetation that would promote triggering by wind in front of the camera was cleared. Despite the nocturnal behaviour of the target species, camera traps were set to record photographs 24 hours a day. Trophy Cam ® (Bushnell Outdoor Products, USA) cameras had continuous triggering of a one-second interval between consecutive images while ScoutGuard ® cameras were set to record 10 s video footage each time a movement was detected within the distance range (15 m). The date and time were shown on each photograph/video. The objective was 60 consecutive days periods of observation but the period was sometimes shortened in the case of poacher activity around the camera traps. All images were downloaded from the cameras after which the date and duration of each observation of suids were entered into MS Excel, each record reflecting an event per specific camera trap station (an event is an observation of at least one suid within a single 30-min time interval). The following were recorded a) camera trap station ID b) GPS coordinates of the camera, c) habitat in which the camera trap was installed d) bushpig count (the total number of animals seen for all the pictures taken during one event on a camera trap station) e) duration of each event f) time duration since the previous event. Wild suid rate is the number of wild suid individuals (bushpig or warthog) photographed per camera day. Likewise, events are the number of events per camera day. Due to the small sample size of suid observations in the sand and bushveld habitats, these two vegetation types were merged into a single category. Log transformation of raw data was performed to obtain a normal-like statistical distribution of abundance values. A 1-way ANOVA was performed for detecting differences in wild suid rate between habitats.