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Preference for various nest box designs in farmed

ž

/

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silver foxes Vulpes

Õ

ulpes and blue foxes Alopex

/

lagopus

L.L. Jeppesen

)

_{, V. Pedersen, K.E. Heller}

Zoological Institute, UniÕersity of Copenhagen, TagensÕej 16, DK-2200 Copenhagen N, Denmark Accepted 10 November 1999

Abstract

Nest box choice experiments were carried out outside the breeding season on adult silver and blue fox vixens with no previous permanent nest box experience. Nest boxes were varied in height of placement, number of rooms, presence of entrance room or platform and light conditions. Only one parameter was varied in any one experiment. Both fox species clearly preferred an elevated multi-room nest box; while silver foxes showed preference for boxes supplied with a platform, blue foxes preferred boxes with an entrance room. There was no significant box preference with respect to light conditions. The possible welfare implications of the preferences are discussed.

q_{2000 Elsevier Science B.V. All rights reserved.}

Keywords: Silver foxes; Blue foxes; Nest box; Preferences; Animal welfare

1. Introduction

Ž . Ž .

Farmed silver foxes VulpesÕulpes and blue foxes Alopex lagopus are

tradition-ally raised in wire mesh cages containing an elevated shelf or platform. During spring, mated vixens are given access to a wooden breeding box placed on the cage floor.

The wild ancestor of farmed silver foxes, the red fox, uses dens for giving birth and rearing cubs. Unoccupied dens have also been reported to be occasionally used for

Ž .

refuge by single animals throughout the year Tembrock, 1957; Henry, 1986, 1996 .

)_{Corresponding author. Tel.:q45-3532-1304, fax:q45-3532-1299.}

Ž .

E-mail address: lljeppesen@zi.ku.dk L.L. Jeppesen .

0168-1591r00r$ - see front matterq_{2000 Elsevier Science B.V. All rights reserved.} Ž .

The arctic fox, which has given rise to the farmed blue fox, also uses dens for breeding. These and other natural or man-made shelters are frequently visited during the rest of

Ž .

the year in the wild Eberhardt et al., 1983 . Thus, wild ancestors of both of the commercially held fox species may seek refuges throughout the year for various purposes as part of their natural life. Based on this knowledge, several attempts have been made during the last decade to clarify how permanent access to shelters affects farm-bred foxes in traditional cages, and especially to reveal possible effects on the welfare of the animals.

It has been demonstrated that farmed foxes use artificial shelters in the cages, but that the extent of retreat to shelters appears species-specific and depends on other factors, such as time of day, season, shelter design, and placement of the shelter. In autumn and winter, silver fox vixens provided with year-round nest boxes use the boxes between 5%

Ž .

and 25% of their time when left undisturbed Jeppesen and Pedersen, 1991 . In the same study, vixens, having access to nest boxes showed lower base levels of cortisol, were less fearful towards humans and were more activerexplorative in an open-field test than traditionally held controls; these differences all indicate less stress among animals provided with nest boxes. In choice experiments involving three differently designed

Ž .

boxes, Pedersen and Jeppesen 1993 showed that during autumn and winter both silver and blue fox vixens use shelters and prefer a nest box placed at the top of the cage supplied with an underlying shelf or platform. Silver foxes spend most time on the platform, while blue foxes seek shelter inside the box. When disturbed, silver foxes flee to remote areas of the cage, while blue foxes retreat to the preferred nest box.

Ž .

Mononen et al. 1998b found that silver foxes provided with a nest box on the cage floor and a platform placed high in the cage spend only 2% of their time inside the nest

Ž .

box, but a considerable amount of time 17–92% either on the platform or on the roof of the nest box.

Given the choice between a cage with an open view and a cage with a partly obscured view, silver and blue foxes appear to prefer the open view for both activity and

Ž .

resting Mononen et al, 1998a . Ž .

Harri et al. 1998 examined production-related parameters and behaviour in growing blue fox cubs given access to either a top-mounted nest box or a wire mesh platform. They found no substantial differences, except that cubs provided with a nest box appeared to be more fearful. This effect could be related to reduced human contact ŽPedersen, 1991 . Comparisons of the reproductive performance of blue fox vixens. supplied with a top-mounted nest box or a traditionally placed breeding box on the cage

Ž .

floor showed no differences related to the two box types Mononen et al., 1999 . Thus, it appears that providing farmed foxes with year-round access to a top-mounted nest box or a platform placed high in the cage may improve the animals’ welfare. However, inter-individual and species differences seem to play a significant role. Moreover, our information on the usefulness of nest boxes and platforms has been based on experimental situations in which there have been simultaneous differences in both placement and design of available box types for individual animals. In order to obtain proper information about the importance of the placement and other aspects of the nest boxes provided, experimental conditions have to be designed in which only a single parameter is varied.

In the present study, we aimed at investigating adult silver and blue fox vixens’ preference for differently placed nest boxes with respect to height. Moreover, we attempted to evaluate the animals’ preferences for box types with a varying number of rooms, with entrance rooms or platforms and, finally, preferences between dark nest boxes and light nest boxes with a transparent roof. Individual foxes with no previous permanent box experience were given free choice between two boxes that only differed by a single parameter.

2. Animals, materials and methods

2.1. Subjects and housing

Ž . Studies were carried out during autumnrwinter using adult silver fox Ns50 and

Ž .

blue fox Ns50 vixens in their first year of life. The animals were randomly chosen from the unrelated offspring of 200 vixens of each species. Litters were raised under

Ž .

conventional farm conditions in 75=100=120 cm H, W, D wire cages. Experimen-tal animals were transferred to individual housing in two-row fox sheds with equally distributed roof windows and with five cages in each row. The cages measured

Ž .

75=200=200 cm H, W, D and were divided by a central partition with a small opening allowing the animals to move freely between the left and right compartments. Solid plates between the experimental cages obstructed the animals’ view to neighbours

and the cages were either left bare or supplied with a nest box in each of the compartments. There were three types of nest boxes all made on the basis of a closed

Ž .

plywood box measuring 40=40=120 cm H=W=D and supplied with two internal

Ž .

partitions dividing the box into three equally sized rooms 40=40=40 cm . Admission to the box was possible through 20-cm circular holes in the front and in the two internal partitions. Closing the holes in one or two of the internal partitions reduced the number of accessible rooms in the box. Removing the roof, front, and the cage-directed wall of the first room and closing the hole in the innermost partition left a platform in front of a one-room box with free view to the cage. Replacing the roof with transparent material

Ž .

increased the light conditions in a three-room box see Fig. 1 . 2.2. Design

Ž . Each species group was randomly divided into five experimental groups Ns10 , which were subjected to the following choice conditions and periods in separate fox

Ž . Ž

houses: 1 the left or right compartment in an empty experimental cage for 2 silver

. Ž . Ž .

foxes or 4 weeks blue foxes ; 2 the left or right compartment supplied with a high or

Ž . Ž .

low difference in height 35 cm placed three-room nest box for 8 silver foxes or 16

Ž . Ž . Ž .

weeks blue foxes ; 3 a three-room or one-room box for 2 silver foxes or 8 weeks

Table 1

Silver fox vixens choice experiments

Experimental condition, experimental week, calendar month, and percent distribution of the elements position

ŽPos. , acti. Õe Act. passiŽ . Õe Pas. , and in nest box Box in the left- and right-hand compartments.Ž . Ž .

Ž .

Exp. condition Exp. weekr Mean percent recordings Ns10 calendar month

Left Right Left Right

Pos. Act. Pas. Box Pos. Act. Pas. Box

No box no box 1rNov 52 17 35 – 48 19 29 –

No box no box 2rNov 55 19 37 – 45 20 24 –

UU UU

Box high box low 1rDec 56 15 25 16 44 20 20 4

UUU

Box high box low 2rJan 60 17 20 23 40 20 17 3

UU UU U

Box high box low 3rJan 60 14 28 18 40 12 17 1

UU UUU UU

Box high box low 4rJan 64 15 30 19 36 15 19 2

Box low box high 5rFeb 45 20 15 10 55 21 27 7

Box low box high 6rFeb 45 10 25 10 55 16 31 8

U UU U

Box low box high 7rFeb 40 13 19 8 60 17 31 12

U UUU U

Box low box high 8rFeb 36 14 20 2 64 18 30 16

UU UUU UUU

1 Room 3 room 1rOct 29 15 13 1 71 22 27 22

U UU UUU

1 Room 3 room 2rOct 32 15 14 4 68 22 28 18

UUU UUU

Platf. entrance room 1rDec 66 18 16 32 34 17 12 5

UUU UUU

Platf. entrance room 2rDec 67 21 15 30 33 17 12 4

Light dark 1rJan 43 10 9 24 57 14 12 31

Light dark 2rJan 39 9 5 23 61 15 7 40

U p-0.05. UU

p-0.01. UUU

Table 2

Blue fox vixens choice experiments

Experimental condition, experimental week, calendar month, and percent distribution of the elements position

ŽPos. , acti. Õe Act. passiŽ . Õe Pas. , and in nest box Box in the left- and right-hand compartments.Ž . Ž .

Ž .

Exp. condition Exp. weekr Mean percent recordings Ns10 calendar month

Left Right Left Right

Pos. Act. Pas. Box Pos. Act. Pas. Box

No box no box 1rNov 47 18 29 – 53 20 33 –

No box no box 2rNov 50 17 33 – 50 15 35 –

U

Box high box low 1rDec 56 8 30 21 41 7 19 15

U U

Box high box low 4rDec 62 9 28 25 38 6 21 11

UUU UUU

Box high box low 8rJan 70 7 29 34 30 5 21 4

UU UU

Box high box low 12rFeb 61 7 26 28 39 7 25 7

Box low box high 13rFeb 55 12 29 14 45 13 21 11

Box low box high 14rMar 61 15 31 15 39 12 16 11

U UU

Box low box high 15rMar 41 10 19 12 59 9 32 18

UU

UU U

Box low box high 16rMar 37 14 8 15 63 11 29 23

U

1 Room 3 room 1rNov 43 8 24 11 57 10 25 22

U

1 Room 3 room 2rNov 41 7 24 10 59 10 26 23

UUU

UU UU

1 Room 3 room 7rDec 22 5 9 6 78 10 23 45

UU UUU UUU

1 Room 3 room 8rDec 23 7 9 7 77 8 27 42

UU U

Platf. entrance room 1rJan 33 7 21 6 66 10 15 41

UU U

Platf. entrance room 2rFeb 37 9 22 6 63 9 17 37

Light dark 1rFeb 52 10 21 21 48 8 19 21

Light dark 2rMar 41 9 29 20 59 13 22 24

U p-0.05. UU

p-0.01. UUU

p-0.001.

Žblue foxes ; 4 a one-room nest box with an entrance room or a one-room box with a. Ž . Ž .

platform for 2 weeks in both species; and 5 a dark or light three-room nest box for 2 weeks in both species. Height of boxes under condition 2 was switched between the left

Ž . Ž .

and right compartments after 4 silver foxes or 12 weeks blue foxes . Likewise, under condition 2, access to the area above and below the boxes was prevented by vertical wire mesh. Under conditions 3–5, all boxes were placed high in the cages due to the results obtained under condition 2.

Prior to experiments, all animals were allowed a 2-week adaptation period to the experimental conditions. The duration of choice conditions depended upon practical constraints, but was fixed to a minimum of 2 weeks since reliable results were obtained under the first highrlow condition within that period.

The time course of experiments is shown in Tables 1 and 2. 2.3. ObserÕations

After the 2-week adaptation period, foxes were individually video-recorded during weekly sets of five consecutive 24-h periods. Tapes were analysed by scanning

observations every 15 min, giving a total of approximately 480 observationsr individ-ualrweek. The following elements were recorded:

Position in left and right compartments ActiÕe in left and right compartments

PassiÕe in left and right compartments

In left or right nest box

2.4. Statistical analysis

Ž .

Wilcoxon tests Siegel and Castellan, 1988 were applied to individual scanning observations within each experimental group. Levels of significance as indicated in the tables imply that 0, 0–1, or 1–2 individuals chose differently at p-0.05, p-0.01, and p-0.001, respectively.

3. Results

The results are presented in Tables 1 and 2 for silver and blue foxes, respectively. Means of scanning recordings are shown as percentages for the 10 individuals in each experimental group.

There were no differences in cage-side preference when the animals were offered an empty cage. Both silver and blue fox vixens preferred three-room nest boxes placed high in the cage. After changing placement of the three-room nest boxes with respect to height, both species showed equal use of low and high place boxes for a 2-week period, but subsequently high place boxes were preferred again. Three-room nest boxes were used more than one-room boxes in both species. Silver foxes preferred one-room nest boxes supplied with a platform, while blue foxes preferred one-room nest boxes with an entrance room. There were no significant differences in use of dark and light boxes, although silver foxes showed a tendency towards a dark preference. Passive stays in the two cage compartments coincided with the side of preferred nest box for resting or retreat, whereas activity was more equally distributed.

4. Discussion

The present study clearly demonstrates that outside the breeding season, both silver and blue fox vixens use nest boxes when provided in an otherwise barren wire mesh cage milieu. The animals spent between 12% and 45% of their time in the preferred boxes, considerably more than the few percent previously found by Mononen et al. Ž1998b and slightly more than the 5–25% reported by Pedersen and Jeppesen 1993 . In. Ž . the study by Mononen et al., however, nest boxes were placed on the cage floor and the cages were only half the size of those offered in the present study. Moreover, in the study of Mononen et al., vixens had the choice of an elevated platform and could use the

nest box roof for resting, which they actually did for a considerable amount of time. The discrepancy in nest box use between the studies could be explained by the animals’ preference for high positions andror the differences in cage size. A nest box placed on the floor restricts the free floor area of the cage further and, as a result, the preference for a platform or the nest box roof may be simply due to the platform or roof acting as

Ž .

extra space as already pointed out by Mononen et al. 1998b . In the study of Pedersen Ž .

and Jeppesen 1993 , the cages were also smaller than the cages in the present study, Ž .

and as in the study of Mononen et al. 1998b , a nest box occupied part of the cage floor and an elevated platform was available.

The preferences revealed in the present study rest on choices among relatively small experimental groups and might be accidentally biased. However, the animals were chosen randomly among the unrelated offspring of large and conventionally raised farm populations and kept visually isolated during the experiments. Thus, we assume that the preferences shown are as far as possible unbiased and representative of the present and similarly kept farm populations. Therefore, based on the present results, there seems no doubt that both fox species prefer an elevated multi-room nest box. The preference for

Ž . an elevated nest box supports the findings of Pedersen and Jeppesen 1993 . These authors argue that a high position of the shelter makes it easier to defend and is a better position for showing dominance towards neighbouring conspecifics and defensive

Ž .

behaviour towards humans. Moreover, Henry 1996 reports that the blue fox ancestor, the arctic fox, tends to seek elevated places for both dens and refuges in nature.

Silver and blue fox vixens in the present study preferred three-room nest boxes against one-room boxes. This finding may relate to the fact that both fox species use an entrance tunnel in their natural dens, and that such a tunnel is better mimicked by the

¨

Ž . Ž

three-room boxes in the present study. Moss and Ostberg 1985 and Braastad 1994, .

1996 have previously found positive effects on the reproduction success and other welfare-related parameters of farmed blue and silver foxes when their breeding boxes have an entrance tunnel. It cannot be ruled out, however, that the preference for three-room boxes as it is observed here could be partly due to the larger size of the three-room boxes. A more clear evaluation of the significance of the number of nest box rooms requires additional studies in which the box size is kept constant.

The difference between the two fox species in the use of one-room boxes supplied with a platform or an entrance room was rather pronounced in the present study. Silver foxes spent two-thirds of their time in the cage compartment with a platform-supplied one-room box, while blue foxes to the same extent preferred the cage compartment with a similar box supplied with an entrance room. This is in agreement with the finding of

Ž .

Pedersen and Jeppesen 1993 , and it might indicate the existence of different motiva-tional causes for the use of nest boxes between the two fox species. Blue fox vixens preference for multi-roomed and secluding nest boxes may reflect that the nest box serves more as a hiding place or retreat from external disturbing stimulation than a means of observing the surroundings or resting, which may be main functions for the silver fox. This interpretation is supported by the study of Pedersen and Jeppesen Ž1993 , who found that under disturbance, blue foxes retreat into a top-mounted nest. box, while silver foxes flee to remote areas of the cage. Moreover, the possibility exists that blue foxes prefer nest boxes with an enclosed entrance room anterior to the actual

place for refuge, while silver foxes are contented with access to an anterior platform. We do not know whether these possible differences in response patterns could be due to basically different behavioural strategies towards danger or to differences in the degree of timidity between the two fox species.

There were no significant preferences for dark nest boxes in the present study. Silver foxes showed a slight tendency to chose dark boxes, but the fact that only 2 weeks were given for choice to occur may make it too premature to conclude that the light level is not important for silver foxes.

A discussion of the present results in relation to the welfare of the two fox species raises several points.

If the foxes’ use of nest boxes and their preference for elevated boxes with more than one room reflect improved welfare in the cages, year-round access to such boxes may be recommended in commercial fox farming. For silver foxes, especially, the nest box should be provided with a platform, while blue foxes should have access to secluding boxes supplied with an entrance room. It has to be stressed, however, that simple choice experiments, such as the present one, have to be supported by other studies concentrat-ing on the effects of box access on a variety of other welfare parameters, as in the study

Ž .

of Jeppesen and Pedersen 1991 . The most interesting aspect of nest boxes is not how much they are used, but why they are used. This requires long-term behavioural studies including physiological measures on the consequences of nest box use for the animals

Ž .

under study. Harri et al. 1998 found that growing blue fox cubs with permanent access to a top-mounted nest box develop a greater number of fear-related reactions than cubs

Ž .

supplied only with a platform in the cages. In agreement with Pedersen 1991 , Harri et Ž .

al. 1998 argue that hiding inside the nest boxes affords the foxes less human contact, which may be important for reducing fear responses towards humans. In a study on

Ž .

silver fox cubs, Pedersen and Jeppesen 1990 showed that cubs subjected to early human handling were less fearful towards humans later in life than non-handled controls. Consequently, year-round access to nest boxes, placed and designed as in the present study and clearly preferred by the foxes given free choice, may not be ideal from a welfare point of view.

References

Braastad, B., 1994. Reproduction in silver-fox vixens in breeding boxes with and without an entrance tunnel. Acta Agric. Scand., Sect. A 44, 38–42.

Braastad, B., 1996. Behaviour of silver foxes in traditional breeding boxes and in boxes with an entrance tunnel. Anim. Welfare 5, 155–166.

Eberhardt, L.E., Garrott, R., Hanson, Wc., 1983. Den use by artic foxes in Alaska. J. Mammal. 64, 97–102. Harri, M., Mononen, J., Rekila, T., Korhonen, H., Niemela, P., 1998. Effects of top nest box on growth, fur¨ ¨

Ž .

quality and behaviour of blue foxes Alopex lagopus during their growing season. Acta Agric. Scand., Sect. A 48, 184–191.

Henry, D., 1986. The Red Fox. Smithsonian Institution Press, Washington, DC. Henry, D., 1996. Living on the Edge. Foxes. North Word Press, Minacqua, WI.

Jeppesen, L.L., Pedersen, V., 1991. Effects of whole-year nest boxes on cortisol, circulating leucocytes, exploration and agonistic behaviour in silver foxes. Behav. Processes 25, 171–177.

Mononen, J., Harri, M., Sepponen, J., Ahola, L., 1998a. A note on the effects of an obstructed view on cage choices in farmed foxes. Appl. Anim. Behav. Sci. 61, 79–84.

Mononen, J., Harri, M., Sepponen, J., Korhonen, H., Reikila, T., Ahola, L., 1999. A top box and a floor box as¨

Ž .

breeding nest boxes in farmed blue foxes Alopex lagopus : reproductive performance, use of the boxes

Ž .

and cub carrying. Acta Agric. Scand. 49, in press .

Mononen, J., Korhonen, H., Harri, M., Kasanen, S., 1998b. A comparison of the use of resting platforms and

Ž .

nest boxes in growing farmed silver foxes VulpesÕulpes . Appl. Anim. Behav. Sci. 58, 383–396.

¨

Moss, S., Ostberg, G., 1985. Housing experiments with blue foxes in 1984. Fin. Palstidskr. 19, 120–121.¨

Pedersen, V., 1991. Early experience with the farm environment and effects on later behaviour in silver

ŽVulpesÕulpes and blue foxes Aloplex lagopus . Behav. Processes 25, 163–169.. Ž .

Pedersen, V., Jeppesen, L.L., 1990. Effects of early handling on later behaviour and stress responses in the

Ž .

silver fox VulpesÕulpes . Appl. Anim. Behav. Sci. 26, 383–393.

Pedersen, V., Jeppesen, L.L., 1993. Daytime use of various types of whole-year shelters in farmed silver foxes

ŽVulpesÕulpes and blue foxes Alopex lagopus . Appl. Anim. Behav. Sci. 36, 259–273.. Ž .

Siegel, S., Castellan, N.J., 1988. In: Nonparametric Statistics for the Behavioral Sciences. 2nd edn. McGraw-Hill, New York.

and the cages were either left bare or supplied with a nest box in each of the compartments. There were three types of nest boxes all made on the basis of a closed

Ž .

plywood box measuring 40=40=120 cm H=W=D and supplied with two internal

Ž .

partitions dividing the box into three equally sized rooms 40=40=40 cm . Admission to the box was possible through 20-cm circular holes in the front and in the two internal partitions. Closing the holes in one or two of the internal partitions reduced the number of accessible rooms in the box. Removing the roof, front, and the cage-directed wall of the first room and closing the hole in the innermost partition left a platform in front of a one-room box with free view to the cage. Replacing the roof with transparent material

Ž .

increased the light conditions in a three-room box see Fig. 1 .

2.2. Design

Ž .

Each species group was randomly divided into five experimental groups Ns10 , which were subjected to the following choice conditions and periods in separate fox

Ž . Ž

houses: 1 the left or right compartment in an empty experimental cage for 2 silver

. Ž . Ž .

foxes or 4 weeks blue foxes ; 2 the left or right compartment supplied with a high or

Ž . Ž .

low difference in height 35 cm placed three-room nest box for 8 silver foxes or 16

Ž . Ž . Ž .

weeks blue foxes ; 3 a three-room or one-room box for 2 silver foxes or 8 weeks

Table 1

Silver fox vixens choice experiments

Experimental condition, experimental week, calendar month, and percent distribution of the elements position

ŽPos. , acti. Õe Act. passiŽ . Õe Pas. , and in nest box Box in the left- and right-hand compartments.Ž . Ž .

Ž .

Exp. condition Exp. weekr Mean percent recordings Ns10 calendar month

Left Right Left Right

Pos. Act. Pas. Box Pos. Act. Pas. Box

No box no box 1rNov 52 17 35 – 48 19 29 –

No box no box 2rNov 55 19 37 – 45 20 24 –

UU UU

Box high box low 1rDec 56 15 25 16 44 20 20 4

UUU

Box high box low 2rJan 60 17 20 23 40 20 17 3

UU UU U

Box high box low 3rJan 60 14 28 18 40 12 17 1

UU UUU UU

Box high box low 4rJan 64 15 30 19 36 15 19 2

Box low box high 5rFeb 45 20 15 10 55 21 27 7

Box low box high 6rFeb 45 10 25 10 55 16 31 8

U UU U

Box low box high 7rFeb 40 13 19 8 60 17 31 12

U UUU U

Box low box high 8rFeb 36 14 20 2 64 18 30 16

UU UUU UUU

1 Room 3 room 1rOct 29 15 13 1 71 22 27 22

U UU UUU

1 Room 3 room 2rOct 32 15 14 4 68 22 28 18

UUU UUU

Platf. entrance room 1rDec 66 18 16 32 34 17 12 5

UUU UUU

Platf. entrance room 2rDec 67 21 15 30 33 17 12 4

Light dark 1rJan 43 10 9 24 57 14 12 31

Light dark 2rJan 39 9 5 23 61 15 7 40

U p-0.05. UU

p-0.01. UUU

Table 2

Blue fox vixens choice experiments

Experimental condition, experimental week, calendar month, and percent distribution of the elements position

ŽPos. , acti. Õe Act. passiŽ . Õe Pas. , and in nest box Box in the left- and right-hand compartments.Ž . Ž .

Ž .

Exp. condition Exp. weekr Mean percent recordings Ns10 calendar month

Left Right Left Right

Pos. Act. Pas. Box Pos. Act. Pas. Box

No box no box 1rNov 47 18 29 – 53 20 33 –

No box no box 2rNov 50 17 33 – 50 15 35 –

U

Box high box low 1rDec 56 8 30 21 41 7 19 15

U U

Box high box low 4rDec 62 9 28 25 38 6 21 11

UUU UUU

Box high box low 8rJan 70 7 29 34 30 5 21 4

UU UU

Box high box low 12rFeb 61 7 26 28 39 7 25 7

Box low box high 13rFeb 55 12 29 14 45 13 21 11

Box low box high 14rMar 61 15 31 15 39 12 16 11

U UU

Box low box high 15rMar 41 10 19 12 59 9 32 18

UU UU U

Box low box high 16rMar 37 14 8 15 63 11 29 23

U

1 Room 3 room 1rNov 43 8 24 11 57 10 25 22

U

1 Room 3 room 2rNov 41 7 24 10 59 10 26 23

UUU UU UU

1 Room 3 room 7rDec 22 5 9 6 78 10 23 45

UU UUU UUU

1 Room 3 room 8rDec 23 7 9 7 77 8 27 42

UU U

Platf. entrance room 1rJan 33 7 21 6 66 10 15 41

UU U

Platf. entrance room 2rFeb 37 9 22 6 63 9 17 37

Light dark 1rFeb 52 10 21 21 48 8 19 21

Light dark 2rMar 41 9 29 20 59 13 22 24

U p-0.05. UU

p-0.01. UUU

p-0.001.

Žblue foxes ; 4 a one-room nest box with an entrance room or a one-room box with a. Ž . Ž .

platform for 2 weeks in both species; and 5 a dark or light three-room nest box for 2 weeks in both species. Height of boxes under condition 2 was switched between the left

Ž . Ž .

and right compartments after 4 silver foxes or 12 weeks blue foxes . Likewise, under condition 2, access to the area above and below the boxes was prevented by vertical wire mesh. Under conditions 3–5, all boxes were placed high in the cages due to the results obtained under condition 2.

Prior to experiments, all animals were allowed a 2-week adaptation period to the experimental conditions. The duration of choice conditions depended upon practical constraints, but was fixed to a minimum of 2 weeks since reliable results were obtained under the first highrlow condition within that period.

The time course of experiments is shown in Tables 1 and 2.

2.3. ObserÕations

After the 2-week adaptation period, foxes were individually video-recorded during weekly sets of five consecutive 24-h periods. Tapes were analysed by scanning

observations every 15 min, giving a total of approximately 480 observationsr individ-ualrweek. The following elements were recorded:

Position in left and right compartments ActiÕe in left and right compartments

PassiÕe in left and right compartments

In left or right nest box

2.4. Statistical analysis

Ž .

Wilcoxon tests Siegel and Castellan, 1988 were applied to individual scanning observations within each experimental group. Levels of significance as indicated in the tables imply that 0, 0–1, or 1–2 individuals chose differently at p-0.05, p-0.01, and

p-0.001, respectively.

3. Results

The results are presented in Tables 1 and 2 for silver and blue foxes, respectively. Means of scanning recordings are shown as percentages for the 10 individuals in each experimental group.

There were no differences in cage-side preference when the animals were offered an empty cage. Both silver and blue fox vixens preferred three-room nest boxes placed high in the cage. After changing placement of the three-room nest boxes with respect to height, both species showed equal use of low and high place boxes for a 2-week period, but subsequently high place boxes were preferred again. Three-room nest boxes were used more than one-room boxes in both species. Silver foxes preferred one-room nest boxes supplied with a platform, while blue foxes preferred one-room nest boxes with an entrance room. There were no significant differences in use of dark and light boxes, although silver foxes showed a tendency towards a dark preference. Passive stays in the two cage compartments coincided with the side of preferred nest box for resting or retreat, whereas activity was more equally distributed.

4. Discussion

The present study clearly demonstrates that outside the breeding season, both silver and blue fox vixens use nest boxes when provided in an otherwise barren wire mesh cage milieu. The animals spent between 12% and 45% of their time in the preferred boxes, considerably more than the few percent previously found by Mononen et al.

Ž1998b and slightly more than the 5–25% reported by Pedersen and Jeppesen 1993 . In. Ž .

the study by Mononen et al., however, nest boxes were placed on the cage floor and the cages were only half the size of those offered in the present study. Moreover, in the study of Mononen et al., vixens had the choice of an elevated platform and could use the

nest box roof for resting, which they actually did for a considerable amount of time. The discrepancy in nest box use between the studies could be explained by the animals’ preference for high positions andror the differences in cage size. A nest box placed on the floor restricts the free floor area of the cage further and, as a result, the preference for a platform or the nest box roof may be simply due to the platform or roof acting as

Ž .

extra space as already pointed out by Mononen et al. 1998b . In the study of Pedersen

Ž .

and Jeppesen 1993 , the cages were also smaller than the cages in the present study,

Ž .

and as in the study of Mononen et al. 1998b , a nest box occupied part of the cage floor and an elevated platform was available.

The preferences revealed in the present study rest on choices among relatively small experimental groups and might be accidentally biased. However, the animals were chosen randomly among the unrelated offspring of large and conventionally raised farm populations and kept visually isolated during the experiments. Thus, we assume that the preferences shown are as far as possible unbiased and representative of the present and similarly kept farm populations. Therefore, based on the present results, there seems no doubt that both fox species prefer an elevated multi-room nest box. The preference for

Ž .

an elevated nest box supports the findings of Pedersen and Jeppesen 1993 . These authors argue that a high position of the shelter makes it easier to defend and is a better position for showing dominance towards neighbouring conspecifics and defensive

Ž .

behaviour towards humans. Moreover, Henry 1996 reports that the blue fox ancestor, the arctic fox, tends to seek elevated places for both dens and refuges in nature.

Silver and blue fox vixens in the present study preferred three-room nest boxes against one-room boxes. This finding may relate to the fact that both fox species use an entrance tunnel in their natural dens, and that such a tunnel is better mimicked by the

¨

Ž . Ž

three-room boxes in the present study. Moss and Ostberg 1985 and Braastad 1994,

.

1996 have previously found positive effects on the reproduction success and other welfare-related parameters of farmed blue and silver foxes when their breeding boxes have an entrance tunnel. It cannot be ruled out, however, that the preference for three-room boxes as it is observed here could be partly due to the larger size of the three-room boxes. A more clear evaluation of the significance of the number of nest box rooms requires additional studies in which the box size is kept constant.

The difference between the two fox species in the use of one-room boxes supplied with a platform or an entrance room was rather pronounced in the present study. Silver foxes spent two-thirds of their time in the cage compartment with a platform-supplied one-room box, while blue foxes to the same extent preferred the cage compartment with a similar box supplied with an entrance room. This is in agreement with the finding of

Ž .

Pedersen and Jeppesen 1993 , and it might indicate the existence of different motiva-tional causes for the use of nest boxes between the two fox species. Blue fox vixens preference for multi-roomed and secluding nest boxes may reflect that the nest box serves more as a hiding place or retreat from external disturbing stimulation than a means of observing the surroundings or resting, which may be main functions for the silver fox. This interpretation is supported by the study of Pedersen and Jeppesen

Ž1993 , who found that under disturbance, blue foxes retreat into a top-mounted nest.

box, while silver foxes flee to remote areas of the cage. Moreover, the possibility exists that blue foxes prefer nest boxes with an enclosed entrance room anterior to the actual

place for refuge, while silver foxes are contented with access to an anterior platform. We do not know whether these possible differences in response patterns could be due to basically different behavioural strategies towards danger or to differences in the degree of timidity between the two fox species.

There were no significant preferences for dark nest boxes in the present study. Silver foxes showed a slight tendency to chose dark boxes, but the fact that only 2 weeks were given for choice to occur may make it too premature to conclude that the light level is not important for silver foxes.

A discussion of the present results in relation to the welfare of the two fox species raises several points.

If the foxes’ use of nest boxes and their preference for elevated boxes with more than one room reflect improved welfare in the cages, year-round access to such boxes may be recommended in commercial fox farming. For silver foxes, especially, the nest box should be provided with a platform, while blue foxes should have access to secluding boxes supplied with an entrance room. It has to be stressed, however, that simple choice experiments, such as the present one, have to be supported by other studies concentrat-ing on the effects of box access on a variety of other welfare parameters, as in the study

Ž .

of Jeppesen and Pedersen 1991 . The most interesting aspect of nest boxes is not how much they are used, but why they are used. This requires long-term behavioural studies including physiological measures on the consequences of nest box use for the animals

Ž .

under study. Harri et al. 1998 found that growing blue fox cubs with permanent access to a top-mounted nest box develop a greater number of fear-related reactions than cubs

Ž .

supplied only with a platform in the cages. In agreement with Pedersen 1991 , Harri et

Ž .

al. 1998 argue that hiding inside the nest boxes affords the foxes less human contact, which may be important for reducing fear responses towards humans. In a study on

Ž .

silver fox cubs, Pedersen and Jeppesen 1990 showed that cubs subjected to early human handling were less fearful towards humans later in life than non-handled controls. Consequently, year-round access to nest boxes, placed and designed as in the present study and clearly preferred by the foxes given free choice, may not be ideal from a welfare point of view.

References

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Eberhardt, L.E., Garrott, R., Hanson, Wc., 1983. Den use by artic foxes in Alaska. J. Mammal. 64, 97–102. Harri, M., Mononen, J., Rekila, T., Korhonen, H., Niemela, P., 1998. Effects of top nest box on growth, fur¨ ¨

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