Wild boar behaviour during live-trap capture in a corral-style trap: implications for animal welfare

Abstract

Background Wildlife traps are used in many countries without evaluation of their effect on animal welfare. Trap-capture of wild animals should minimise negative effects on animal welfare, irrespective of whether the animals are trapped for hunting, research, or management purposes. Live-trap capture of wild boar (Sus scrofa) followed by killing inside the trap by gunshot is a recently introduced but disputed hunting method in Sweden. Approval of trap constructions is based on gross necropsy findings of 20 trapped and shot wild boars. For improved animal welfare evaluation, our aim was to study wild boar behaviour during live-trapping in a 16 m2 square corral-style trap. Behavioural assessments were conducted after filming 12 capture events of in total 38 wild boars (five adults, 20 subadults, 13 piglets). Selected behavioural traits were compared with pathological changes (trap-related lesions) found at necropsy of the 20 subadults, to determine if these variables were useful proxies of capture-induced stress in wild boar. Results The wild boars spent less time resting in the evening than in the night and morning. Using Friedman’s ANOVA, there was an overall difference in the time spent foraging. However, we only found a difference between the evening and morning in the Wilcoxon matched pairs test after the Sequential Bonferroni correction, where the wild boars spent more time foraging in the evening than in the morning. Single captured individuals showed more escape behaviours and reacted more strongly to external stimuli than individuals captured in a group. It was more common for animals to charge against the mesh walls of the trap upon human approach compared to upon initial capture when the trap door closed. Trap-related pathological findings due to trauma were documented in 13 of the 20 subadults that were necropsied. Behavioural alterations indicative of capture-induced stress (e.g. charging into the trap walls) were documented in trapped wild boars with no or minor physical injuries (e.g. skin abrasions, subcutaneous haemorrhage). Conclusions Behavioural assessment provided valuable information for determination of capture-induced stress in wild boar when evaluating live-trapping in a corral-style trap, whereas pathological evaluation through necropsy did not fully reflect the animal welfare aspects of live-trapping. We emphasize the inclusion of species-specific behavioural data assessment for evaluation of capture-related stress during live-trapping and for testing of new trap constructions before approval.

Observation of rescue behaviour in wild boar (Sus scrofa)

“…The first requirement states that the victim is distressed and endangered by physical injury or death. Entrapped wild boars exhibited clear behavioural signs of distress, running in the cage and charging into the walls, possibly trying to escape, which resembles the signs of distress observed during trapping in other studies 43,44 . Wild boar are commonly trapped for management or research purposes.…”

“…In the latter case, they are handled to collect data or to be marked and released 43,45 . In either case, an increasing number of studies confirm that entrapment is extremely stressful for the animals involved, which can suffer from behavioural or physiological distress, immediate physical injuries or pathologies (e.g., capture myopathy or hyperthermia) sometimes resulting in death [43][44][45] . Without a video record, we are not able to say if any distress vocalizations (e.g.…”

Successful treatment of gastrocnemius muscle rupture in a long-tailed goral rescued from a live trap: a case report

“…The goral, in this case, was an individual who unfortunately suffered an accident due to the negative effect caused by the outbreak of ASF in Korea. Currently, wildlife live traps are used worldwide without any assessment of animal welfare [ 7 ]. However, few scientific studies have reported behavioral or physiological harm to wildlife other than target animals caught in various types of traps [ 6 ].…”

“…However, as in this case, wild boars and other wild animals are highly likely to be captured. In addition, live traps can have some negative effects on the health and welfare of wild animals, including trauma, fear, pain, and stress response [ 7 8 9 10 ].…”

A comparison of fragmenting lead-based and lead-free bullets for aerial shooting of wild pigs

“…This species is commonly targeted for culling where they are invasive, covering a wide global distribution [ 22 ]. In their native range, including mainland Europe, wild pigs are managed as a hunting resource [ 23 , 24 ]. Hence, whether for recreational, commercial or professional reasons, many wild pigs are shot worldwide every year.…”