An approach to stress assessment during hunting: Cortisol levels of wild boar (Sus scrofa) during drive hunts

Abstract

Only little is known about the effect of stress (both short-term and long-term) on wildlife species. To get an idea of stress in wildlife, we investigated the cortisol level of wild boar during drive hunts in Lower Saxony, Germany. Cortisol as one of the main stress hormone in mammals is considered to have negative impacts on the animals well-being if expressed excessively (repeatedly over a longer period). We analysed serum cortisol levels of 115 samples using a radioimmunoassay and compared sampling month, hunting grounds, age classes and sexes, as well as possible correlations between cortisol level and weight and pregnancy status of female wild boar. We found that cortisol levels during these drive hunts exhibit wide variation. The mean cortisol level was 411.16 nmol/L with levels ranging from 30.60 nmol/L (minimum) to 1,457.92 nmol/L (maximum). Comparing age groups and sexes, we found significant differences between the sexes, with females having a higher cortisol levels than males. After grouping age groups and sexes together, we also found significant differences based on the age-sex group. We found no correlation between cortisol levels and weight, but significantly higher cortisol levels in pregnant females compared to non-pregnant females. No differences were found between sampling months and locations, respectively. These results show the impact of drive hunts on stress in wild boar; nevertheless, this impact of drive hunts as performed in most parts of Central Europe seems to be not as high as imagined. Still, we need more information about cortisol levels and stress in (hunted) wildlife species.