Maternal behaviour, infanticide and welfare in enclosed European wild boars (Sus scrofa)
European wild boars (Sus scrofa) are kept in Swedish enclosures for hunting and meat production purposes. The sows are known to undergo behavioural changes in connection with farrowing and their natural behaviours may be compromised by the limited area of the enclosure. The general aim of this thesis was to provide detailed quantitative data on wild boar sows when farrowing in captivity and to report whether possible needs can be compromised by the limitations of an enclosure. Specifically, it was aimed to provide a quantitative and functional account of the occurrence of infanticide, and its possible relations to welfare of confined wild boars.
A field study was carried out in a hunting enclosure, where 1200 hours of behavioural recordings and data from 22 farrowings were collected. The farrowing period could be divided into three phases: pre-farrowing, isolation and sociality phases (in relation to farrowing: day -14 to -1, day 1 to 8, day 9 to 14 respectively). The activity decreased during isolation and increased in the sociality phase. The average distance to other individuals increased during isolation and decreased in the sociality phase. Habitat use changed towards more protective habitats after farrowing (Paper I).
Non-maternal infanticide was documented in 14 out of 22 litters. Infanticide, typically performed by an older and larger sow than the mother, caused the deaths of all neonates in all but one affected litters. We found no effect of relatedness. A questionnaire sent to 112 owners of enclosures in Sweden and Finland resulted in 62 responses. Although the owners were often not able to provide exact figures on reproduction and mortality, nonmaternal infanticide was reported to be the most common cause of piglet mortality. The occurrence of infanticide was unrelated to size of enclosure and to variations in husbandry routines. All together results may suggest that non-maternal infanticide is part of the normal behavioural repertoire in wild boars (Paper II).
The studies of this thesis reveals the farrowing period as the most dynamic and perhaps most challenging for wild boar sows in enclosures. There are serious welfare concerns in the husbandry of wild boars in Swedish enclosures. The most obvious welfare problem is non-maternal infanticide, where both sows and piglets are assumed to suffer, and where the outcome from the action must be considered unacceptable. If wild boar husbandry shall be equated with other animal husbandry in our society, it needs to be regulated to overcome many of the presented potential welfare problems in this thesis.
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