Stress Assessment of Wild Boar (Sus scrofa) in Corral-Style Traps Using Serum Cortisol Levels

Abstract

Capture of wild boar in corral-style traps with subsequent culling is increasingly used for population management. The method is debated due to animal welfare concerns making welfare studies in traps necessary. While previous studies focused on behaviour and injuries, this study dealt with the physiological aspect. Cortisol levels in wild boar caught in corral-style traps (50–90 qm2, n = 138) were compared with those killed during single (n = 37) and driven hunts (n = 90). Collected sera were purified by solid phase extraction (SPE) and analysed via radioimmunoassay. Cortisol levels in blood samples were stable under cooled (4–7 °C) conditions for a storage time of up to 87 h before centrifugation. Cortisol levels were significantly higher in wild boar killed in corral-style traps than during driven hunts and single hunts. Wild boar caught in groups of five or more showed lower cortisol levels than single animals or in smaller groups. Therefore, time span inside the trap and of culling should be reduced to a minimum, and capturing groups of animals should be preferred to reduce stress. For animal welfare assessment of wild boar live-trapping, additional data from behavioural analyses and pathological examinations must be integrated.

Refining animal welfare of wild boar (Sus scrofa) corral-style traps through behavioral and pathological investigations

“…Since escape behavior can lead to injuries, trapping entire sounders is preferable from an animal welfare perspective. These results are in line with previous studies in which the capture of single individuals is associated with higher cortisol levels and increased escape behaviors than wild boar captured in a larger group [14,24].…”

“…Individually trapped wild boar exhibited more escape behavior and more escape attempts in the presence of humans than at the beginning of trap closure [ 14 ]. Westhoff et al [ 24 ] confirmed this using cortisol levels, showing that wild boars captured in groups had lower cortisol levels than those captured individually. In addition, cortisol levels were higher in wild boar corral-style traps compared to other hunting methods [ 24 ].…”

“…Westhoff et al [ 24 ] confirmed this using cortisol levels, showing that wild boars captured in groups had lower cortisol levels than those captured individually. In addition, cortisol levels were higher in wild boar corral-style traps compared to other hunting methods [ 24 ]. According to Westhoff et al [ 24 ], reliance on cortisol analysis alone is insufficient to assess the welfare of wild boars in corral-type traps.…”

“…Physiological alterations such as increased levels of stress hormone or their metabolites, elevated body temperature and blood pressure or changes in hematological variables has been used for animal welfare evaluation in trapping [ 13 , 20 , 23 , 24 ]. The capture of free-ranging wildlife can cause a stress response [ 25 ].…”

“…Excessive escape behavior in particular leads to injury and thus indicates capture-related stress. Therefore, combining pathological examinations with behavioral analyses and physiological parameters is crucial for an animal welfare assessment [ 18 , 24 , 30 ].…”