Maternal infanticide and periparturient behaviour in farmed silver foxes Vulpes vulpes

Abstract

This study aimed at describing and searching for causes of infanticide by farmed silver-fox vixens. Reproduction and periparturient behaviour were studied in 21 litters of primiparous and 18 litters of multiparous vixens by video-recording inside the breeding box. Of 54 dead cubs, 41 had been bitten and probably killed. The probability that a cub with a primiparous mother would be killed was 37%. Seventeen vixens were categorized as infanticidal. Primiparous vixens killed cubs shortly after birth, whereas multiparous ones showed normal maternal behaviour during parturition and killed later. Cubs were not killed more often during working hours. A longitudinal study including nine cub-killers showed that they usually repeated such behaviour in subsequent years. Half of the infanticidal vixens bit off the tails of their offspring prior to killing them. Dead cubs were treated as prey, often buried under wool tangles and later eaten, whatever the cause of death. A quantitative analysis of behaviour was made by instantaneous sampling of 19 vixens (12 infanticidal). Cub-killing vixens and vixens which reproduced normally, in general, showed quite similar time-budgets of behaviour. Cub-killers also groomed cubs as frequently as non-killers, but stood more often when grooming, and showed more self-grooming and less resting inside the box during the first day post-partum. Environmental disturbances or social pathology were considered unlikely to be significant causes of cub-killing on the farm. Although several similarities were found with infanticide in other farm animals, infanticidal vixens did not show severe behavioural abnormalities.