Blue foxes' motivation to gain access to solid floors and the effect of the floor material on their behaviour

Farmed blue foxes are willing to work to gain access to a sand floor from a wire mesh floor. It is not clear whether the foxes work for the sand floor because of its solidity or because it enables them to perform certain behaviours, e.g. exploration and digging. Here, we measured blue foxes' motivation to gain access from a wire mesh floor to a floor with 15-30cm deep sand, a floor with 3-4cm deep sand, a solid concrete floor, and another wire mesh floor. In addition, we analysed the foxes' behaviour on these floor materials. Seven male blue foxes were trained and tested in self-constructed operant apparatuses. In an apparatus, the fox could move a bottomless test cage from a wire mesh floor to a neighbouring, alternative floor material for a 4-min visit by pressing a lever in the test cage for a fixed number of times (Fixed Ratio, FR). The foxes worked for each floor material for 12 days. In each daily test session, the foxes were exposed to work on one of the four workloads (FR 6, 12, 24, 48), for 3h. The behaviour of the foxes was analysed during the 4-min visits on each floor material. The results showed that there was no difference between the floor materials, either in the demand elasticity of the fragment of the demand curve (ranging from -0.46 to -0.33), or in the intensity of the demand. However, the foxes' behaviour varied between the floor materials. More digging, play, rooting (exploration with the muzzle), and vole jumping were observed on the floor materials with sand, than on the concrete floor and the wire mesh floor. Both the presence and the depth of the sand layer stimulated these behaviours. It is concluded that juvenile blue foxes do not value solid floor materials more than a wire mesh floor. However, the sand floor stimulates more digging, play, vole jumping, and exploration than the concrete floor or wire mesh floor. Furthermore, the depth of sand may be an important factor in eliciting these behaviours. Access to a floor material with sand may improve the welfare of farmed blue foxes by providing the possibility to perform species-specific behaviours.