Field comparison of three restraint techniques for deploying GPS collars on wild pigs (Sus scrofa)

Context Spatial behaviour research involving GPS tracking is increasingly being used to support the management of wild (including feral) pigs (Sus scrofa) around the globe. Capturing and collaring pigs can have severe impacts on their health and welfare, but the implications of different capture and restraint methods practiced in large-scale studies remain unclear. Aims We compared the effectiveness and animal welfare outcomes of three methods for restraining wild pigs for GPS collar deployment: (1) remote darting with tiletamine-zolazepam and xylazine (TZX), (2) pole syringe injection with tiletamine-zolazepam (TZ), and (3) manual restraint without chemical immobilisation. Methods We retrospectively analysed data from 360 collaring events across three independent collaring programs in Australia. We quantified the durations of procedures, the frequency of adverse events (e.g. hyperthermia, mortality), and post-release movement patterns using a standardised animal welfare assessment framework. Key results Manually restrained pigs experienced the shortest exposure to capture and handling stressors, and showed no increase in adverse outcomes compared to chemically immobilised pigs. Pigs darted with TZX had more variable induction and recovery times than those administered TZ via pole syringe, but the use of reversal agents (yohimbine, atipamezole) reduced overall handling time. Pole syringe immobilisation with TZ produced more consistent inductions but longer recumbency durations. Post-release movement patterns were similar across all methods, with minor behavioural disruptions for about 4 days. Conclusions Manual restraint is a viable option for telemetry studies where experienced handlers are available and extended procedures are not required. When chemical immobilisation is desirable, animal welfare outcomes can be improved by using drug combinations with reversal agents and by applying careful monitoring and intervention. Implications These findings support evidence-based refinement of wild pig capture protocols and highlight the importance of publishing animal welfare outcomes to inform best practice in wildlife research and management.