Extensive infanticide in enclosed European wild boars (Sus scrofa)

Infanticidal behaviour, behaviour with wide welfare implications, is wide-spread among animals of various taxonomic groups, but has not previously been systematically studied in European wild boars, which are commonly kept in enclosures in Sweden and Finland for meat and recreation hunting. We studied the behaviour of wild boars in one enclosure during three reproductive seasons. Non-maternal infanticide was documented in 14 out of 22 litters, causing the deaths of all piglets in all but 1 affected litters. Infanticide was typically performed during or shortly after parturition by a sow which was older (P < 0.05) and tended to be larger (P = 0.068) than the victimised sow, and was not affected by whether or not the involved females were mother–daughter pairs. A questionnaire sent to 112 owners of a total of 116 enclosures in Sweden and Finland resulted in 62 valid responses. Non-maternal infanticide was reported to be the most common cause of piglet pre-weaning mortality, which in total (including all causes) was estimated to be 29.1%. The occurrence of infanticide was unrelated to size of enclosure (less or more than 20 ha) and to variations in supplementary feeding routines (less or more than once a week) (P > 0.05), which may suggest that the behaviour could be a part of the normal behavioural repertoire in European wild boars. The observed levels of infanticide constitute a major welfare problem in captive wild boars.