Group housing of adult silver fox (Vulpes vulpes) vixens in autumn: Agonistic behaviour during the first days subsequent to mixing

Due to farmed foxes’ (Vulpes vulpes) social flexibility and possible motivation for intraspecific contact, group housing may act as an alternative housing procedure. Because initial social contact between silver foxes usually involves agonistic displays as a part of foxes’ social dominance assessments and owing to their territorial motivation, the incidence of serious aggression may put foxes’ welfare at risk. The aim of this study was to investigate the consequences of housing adult silver fox vixens in triplets of various age compositions on their agonistic behaviour, body weight gain and bite injury level following the first hours and days after mixing in triplets. Ninety 1.5 and 2.5-year old vixens were housed in triplets consisting of four different age compositions (N = 3 × 6 × 4 = 72) and in one singly housed control group (N = 18) in September. Group 112 consisted of two 1.5-year olds and one 2.5-year old; Group 221 of two 2.5-year olds and one 1.5-year old; Group 111 of 1.5-year olds and Group 222 of 2.5-year olds. The triplets were housed in standard wire mesh cages connected with openings and with access to top nest boxes. The foxes’ behaviour was recorded continuously the three first hours after mixing, 1 h day 2 (26th hour) and 1 h day 3 (50th hour) after mixing. One and two weeks following mixing, the number and severity of bite injuries were assessed. There was no overall difference between groups in observed agonistic behaviours. In all experimental groups aggression was most frequent the first hour (chasing = 7.7 ± 1.2; physical aggressive signals = 2.3 ± 0.32; fights = 2.0 ± 0.23). Overall, number of aggressive interactions was reduced with time (P < 0.001). Scabs and/or bite injuries were recorded in 58.3% of the animals the first week and in 42% the second week. Social grooming and play was only observed at very few occasions. About 35% of the animals, except for controls, lost weight the first week. Vixens with injuries gained less weight compared to unharmed animals (P = 0.03). A negative correlation between weight asymmetry and number of fights was found (r = −0.57, P < 0.01). Although a clear effect of age composition was not found the triplets consisting of 2-year olds might have experienced less negative consequences of group housing because of absence of serious wounds. Due to the frequency and intensity of aggression and the fact that several vixens lost weight during the first week it is most likely that adult silver fox vixens experience the initial phase of social housing as stressful.