The effect of a combination of permanent breeding cage and low housing density on the reproductive success of farmed blue foxes.

Social factors are known to affect the reproduction of many canids both in the wild and in farms. For example, reproduction in farmed silver foxes is regulated by social stress; foxes seem to benefit from noncramped housing conditions and permanent breeding cages. However, no comparable studies have been carried out in farmed blue foxes. The aim of our experiment was to create an alternative, improved, economically viable and practical housing solution for blue foxes. Therefore, we compared reproductive performance of blue foxes in permanent breeding cages with low animal densities (L group, N=79) and traditional housing with its changing social environment with high animal density (H group, N=74). The reproductive data from the L and H groups were compared separately for primiparous and multiparous vixens because the reproductive performance in primiparous vixens was substantially lower (P<0.001) than in multiparous vixens. Altogether, 41 and 39% of the primiparous vixens in the H and L group whelped (P>0.05), but only 28 and 34%, respectively, weaned at least one cub (P>0.05), i.e., 72 and 66% of the primiparous vixens did not reproduce in the H and L group, respectively (P>0.05). The total reproductive performance, expressed as cubs at weaning per breeding female, was 1.7+/-3.5 for the H and 1.6+/-2.9 for the L group (P>0.05). In the primiparous vixens, the only statistically significant difference observed between the two housing systems was that the onset of oestrus occurred five days earlier in the H than in the L group (P<0.05). All multiparous vixens in the L group exhibited oestrus compared to 94% in the H group (P>0.05). Furthermore, there was a nonsignificant (ns) trend for fewer barren females (9% versus 17%), more successfully reproducing vixens (83% versus 74%) and a higher number of live-born cubs (10.9+/-4.7 versus 9.4+/-3.9) in the L than in H group in the multiparous vixens (for all P>0.05). This resulted in 1.7 and 1.4 cubs more per breeding and per mated vixen, respectively, at weaning in the L group (7.3+/-5.0) compared to the H group (5.6+/-4.2), but also this difference was nonsignificant. Although our present results lack statistical significance, they are promising enough to encourage field experiments with sufficiently large number of animals to prove or disprove these preliminary findings that lower housing density and permanent breeding cage, together or separately, may enhance reproduction particularly in multiparous blue fox vixens.

Trade-off between floor level and floor material in farmed silver foxes.

Farmed silver foxes (Vulpes vulpes) were allowed to balance their known preference for an elevated floor against their presumed preference for a sand floor. In Experiment 1, foxes had to choose between two identical cages, connected with an opening. One cage had a wire floor and the other had a sand floor, but the cages either were on the same (low or elevated) or on different levels (one cage 40 cm higher than the other). In Experiment 2, the cage pairs were connected with a 1.2 m long wire-mesh tunnel, one cage was always on a higher level (50 cm) than the other. In Experiment 1, foxes always preferred the sand floor during their active time. They also preferred the sand floor for resting, if it was on the same level as wire floor, but did not show any genuine preference if the floors were on different levels. In Experiment 2, foxes never preferred the lower floor. They preferred the elevated sand floor for activity and the elevated wire floor for lying. When two floors were identical they preferred the elevated one. Their rest consisted of 11-22 bouts, a major part of these being spent in the preferred cage. They also preferred a previous lying site to a new one, often exclusively and independently of floor material. In Experiment 1 foxes preferred the sand floor whereas in Experiment 2 they preferred the elevated floor indicating that the ability of a trade-off situation to rank resources depends on the method it is inflicted.

Preferences of farmed blue foxes for different floor types.

In the first experiment, farmed blue foxes were allowed to choose for 1 week between four standard farm cages equipped with different floor materials: plastic-coated wire mesh, dry wood, dry sand and wet (summer) or icy (winter) sand. Resting consisted of 10-15 separate bouts/day occupying 50-60% of the total 24-h. There were no other differences in the use of the cages except that the time spent on, and the duration and number of resting bouts were lower on wet or icy sand, resting periods being more affected than activity. In the second experiment, two cages were connected with a 1.2 m tunnel. One cage was always elevated (50 cm) compared to that one which was lower. One cage of each pair had a wire floor whereas the other cage either had sand or wire floor. Sand floor was preferred for active behaviours and wire floor for resting if these were on elevated level. Of two identical wire-floored cages, the elevated one had the priority. Foxes preferred to rest on the same floor where they had finished their previous resting bout, often exclusively and independently of floor material or floor level.