Do growing pigs build sleeping nests? : a behavioural study in domestic pigs and European wild boar

Sammanfattning: The domesticated pig, Sus scrofa domesticus, has long been used for meat produc-tion. Its wild relative, the wild boar, Sus scrofa scrofa, gives an important possibil-ity to study some aspects of the domestication process. Thereby increasing our knowledge of important behaviours that may still exist in our domestic pigs. The aim of this master thesis was to perform an observational field study in which the main focus was to study if growing slaughter pigs perform behaviours that could be seen as the building of sleeping nests. A comparative study with European wild boar (Sus scrofa scrofa) kept in a large, outdoor enclosure was performed to see if they build sleeping nests, and what behaviours they perform in relation to lying down. A total of 158 domestic pigs in two age categories on a Swedish, KRAV-organic pig farm were included in the study, as well as four European wild boar. 84 domestic pigs aged 13 weeks were studied in their hut when kept on their sum-mer pasture, and 74 domestic pigs aged 5 – 6 months were studied when kept in-doors in large pens with deep straw bedding. The four European wild boars were approximately 1 year old and studied in their 4 ha large forest enclosure. The animals were studied by camera recordings between June and September 2019. All animals were included to increase the likelihood of observing behav-iours in relation to lying down and resting or sleeping. Behaviours considered relevant from a nest-building perspective were those that in some way manipulat-ed the ground. In this study, these were rooting, pawing, plowing, arranging mate-rial and lastly, kneeling and rooting. The results indicate that a majority of both domestic pigs and European wild boar perform at least one behaviour that manipulates the ground before lying down. No differences were found in mean number of relevant behaviours per-formed between the groups, nor were there any differences between most of the different relevant behaviours between the groups. Only plowing differed between the groups. Rooting was the most common behaviour performed in all three ani-mal categories. Further studies are needed to properly evaluate the possible nest-building in growing domestic pigs as well as European wild boar.