CHOICE OF SIDE OF RESTING POSITION IN ... - Science Direct

Behavioural o Elsevier

4 (1979) Publishing

Processes, Scientific

129-144 Company,

CHOICE OF SIDE OF RESTING

GUNTER

Sektion

129 Amsterdam

POSITION

-

Printed

in The Netherlands

IN VULPES VULPES (L.)

TEMBROCK

Biologie,

(Accepted

Humboldt-UniversitCt

4 September

zu Berlin (German Democratic

Republic)

1978)

ABSTRACT Tembrock,

Processes,

G., 1979.

Choice

of side of resting

position

in Vulpes vulpes (L.).

Behav.

4: 129-144.

In fifteen foxes held under laboratory conditions all behaviour data recorded were tested according to the foxes’ resting positions and especially as to the direction in which the body lay curled up (to the right or the left). 29 055 single items of data could be extracted and processed statistically. All individuals taken together show a significant preference for the right direction in the resting position. If the data are separated according to sex the statistical significance is restricted to the males. The difference between males and females is significant. The analysis indicated individual differences; individual disposition with regard to preference for one side seems plausible. Statistical testing of the foxes by twos indicated variations correlated with the biosocial status. The dominance value is positively correlated with the tendency to prefer a resting position to the left. There are significant differences between two times of day (09.00-11.00; 17.00-19.00 h) and two times of year (December-March; June-August) with respect to the type of behaviour studied. These differences refer to mean values and variance.

INTRODUCTION

The red fox, Vulpes uulpes (L.), exhibits a number of different positions taken up during rest (cf. Tembrock, 1957; Hassenberg, 1965). In the typical position encountered during longer periods of rest and actual sleep the body lies curled up and on the belly, the snout is placed under the tail and the upper part of the thigh, the tail being positioned outside and over the hind-legs and snout. The ear which, according to the turn of the body, is on the outside points outwards whereas the other points forwards. The intensity of resting appetence can be derived from the degree to which the body is curled up. The latter, however, is also influenced by the temperature of the surroundings. This type of position permits two alternatives, either the body is turned to the right (Fig.1) or to the left. Tembrock (1957) stated a preference of 71.6% for the left side in a female based on 169 observations, and 47.4% in a male (n = 344). At the time we did not go into this question further. However, a

Fig.1. Resting posture of Vulpes uulpes, three phases of the consummatory No. 12).

action (male

more detailed analysis shows that the decision concerning left or right side position appears to be influenced by a number of environmental factors. Although a number of studies on lateral preferences in animals and man have been published (e.g. Stier, 1911; Ludwig, 1932; Grzimek, 1949; Wegener, 1953; Oeser, 1969; Weidauer, 1973) little is known on causal connections. Weidauer (1973) found no significant right or left preference in general in his observations on primates (in particular anthropoids) involving the speciesspecific actions of one hand, although he found this was certainly the case for acquired motor actions as, for instance, those involving objects of human origin. Most studies concerning this problem relate to the use of bilaterally arranged systems of organs but not to spatial alternatives in the total behaviour of an organism. In the latter case an essentially different motivation structure prevails which is determined by second order spatial requirements (Tembrock, 1976). Whereas first order spatial requirements are determined by the quantitative body measurements, second order spatial requirements are given by particular motivations and are therefore primarily of a qualitative nature, although they naturally also include first order spatial requirements. As the internal state causes the “operator” to determine a behaviour programme leading to the position described above - “curled up on belly” the following three types of environment (Tembrock, 1976) may be involved in the behavioural processes. (1) Environment defined by the organism’s own body. Particular physiol-

131

ogical and morphological factors and the actual situation may influenct the decision to lie in the left or right position: in the latter case the left part of the thorax is in contact with the substratum, and at the same time the left side of the body is turned outwards, thus inducing a greater heat exchange than on the right side. In this case also the right fore-leg is free and will therefore be the first to be used on rising from the rest position. (2) Information environment. All information of semantic significance to the organism is evaluated, e.g. air movements, light gradients, vertical structures used as contact surfaces, background noise, ground conditions, temperature gradients and also general spatial orientation and special stimuli relating to territorial functions (burrow, paths of flight, etc.) - these are the most important factors in determining a resting place. (3) Communication environment. All information deriving from other individuals of the same species is evaluated, e.g. their resting positions or particular behaviour, including social relations to the other individuals and specifically their dominance value (especially as regards individuals of the same sex) and also their ages; these factors can influence the choice of resting position. In addition, all three environmental types share the feature that general forms of state, in particular the endocrinal status, can influence the role each type plays and may change their relative values. The state of the individual is of particular importance in relation to the environmental type defined by the organism’s own body; in this case it is to be expected that individual peculiarities including age will be of influence in causing a systematic deviation from a symmetrical distribution between right and left positions. Even if one assumes that there is no primary preference for one side and that therefore right or left legs can be used with equal facility in erecting the body after rest, there is still the consideration that the asymmetrical anatomical position of the heart could influence the decision in the context of the surrounding environment. The other two environmental types will act in a much more complex manner owing to the number and form of external variables. Apparently, however, no systematic investigations have been carried out as yet with regard to these aspects. It therefore seemed pertinent in this context to analyse the rather copious data on foxes recorded from 1950 to 1956 which we have at our disposal. MATERIAL

AND METHODS

The records of fox behaviour which formed the basis of the 1957 analysis (Tembrock, 1957) were evaluated. A total of 29 056 single observations recorded in the period 17 February 1950 to 31 May 1955 were processed. The conditions under which the animals were kept are described in detail in the paper cited above; a room of cross-section 4.90 X 5.00 metres containing several open cages and elevated sections for resting purposes and illuminated by natural daylight was provided. The foxes observed included three

132

litters of a single pair (1952: d; 1953: 999; 1954: dd). In the following, individual foxes are indicated by their numbers in our cataiogue (see Tembrock, 1957): No. 1 (c?), born 1948; No. 2 (O), born 1947; No. 7 ($), born 1949; No. 8 (d), born 1949; No. 11 (d), born 1951; No. 12 (6), imported as adult individual; No. 13 (O), born 1951; No. 14 (d), born 1951; No. 20 (d), born 1952, parents No. 2 and No. 12; No. 22 (O), No. 23 (O), No. 24 (9), siblings born 1953, parents No. 2 and No. 12; No. 26 (d), born 1953; No. 31 (d), No. 32 (d), siblings, born 1954, parents No. 2 and No. 12. Resting positions are indicated by the symbols IA and q in the observational records. All observations of this type were evaluated. Only foxes No. 2 and No. 12 were present during the entire period of observation (after 16 August 51); the others were alternated and thus only present for part of the time. For this reason uniform periods of observation are not available for analysis as only the identical members of a group of foxes were to be considered in a definite time period - the periods considered are therefore not uniform in duration. In Table I, the dates of the periods, the number of observations, and the number of foxes are listed.

TABLE

I

Dates of the periods,

number

of observations

and foxes

observed

No.

Period

n

Nos. of foxes

1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22. 23.

17 Feb.-Z June 1950 3 June-31 Dec. 1950 1 Jan.-4 June 1951 5 June-12 Nov. 1951 13 Nov. 1951-11 Feb. 1952 11 Feb.-29 Apr. 1952 29 Apr.-22 June 1952 23 June-17 Sep. 1952 18 Sep.-20 Nov. 1952 20 Nov.-31 Dec. 1952 1 Jan-18 Feb. 1953 19 Feb.-l0 Mar. 1953 22 June-8 Aug. 1953 8 Aug.-30 Aug. 1953 31 Aug.-l7 Oct. 1953 17 Oct.-l7 Dec. 1953 18 Dec. 1953-10 Feb. 1954 10 Feb.-29 Mar. 1954 30 Mar.-27 June 1954 28 June-10 Sep. 1954 11 Sep.-22 Dec. 1954 23 Dec. 1954-22 Mar. 1955 23 Mar.-31 May 1955

349 427 625 713 772 1718 411 652 1314 1502 2306 794 1567 897 1908 2658 2285 1481 454 1007 1705 2016 1494

1;2;7;8 1; 2; 7; 8 1;2;7;8 1; 2; 7; 11; 12 2; 7; 11; 12; 13 2; 7; 11; 12; 13; 14; 15 2; 12; (and fox-cub) 2; 12; 20 2; 12; 20; 11; 13 2; 12; 20; 11; 13; 14 2; 12; 20; 11; 13; 14 2; 12; 20; 11; 13; 14 2; 12; 22; 23; 24 2; 12; 22; 23; 24 2; 12; 22; 23; 24; 25 2; 12; 22; 23; 24; 25 2; 12; 22; 23; 24; 25; 11 2; 12; 23; 24; 25 2; 12; (and fox-cub) 2; 12; 31; 32 2; 12; 31; 32; 23 2; 12; 31; 32; 23; 11 2; 12; 31; 32; 32; 23; 11

133

The following statistical procedures were applied to test the significance of the data: 1. U-test Z - np

(1)

NY= 4X7)

2. Pair comparison Correlation between foxes was tested using the following procedures 2.1. G-test (Woolfe) (All tests, see Claus and Ebner, 1974) G = S1 + Sz - S3

(2)

where S1 = g= + gb + gc + gd and

(table of four fields)

g = 2n - In n Sz =g,

(edge sums)

S3 = g

2.2. t-test (3)

fl =:

f2 A

nlfl

q=l-p

P= nl

n2

+n2f2 +n2

2.3. The tetrachoric coefficient 180”

r(tet) = cos (I+&

(4)

) ad

2.4. x2-test (Yates)

x2 = (a+b) - (a+c) * (b+d)

(5)

* (c+d)

2.5. Mean values are compared with the t-test (Welsh) All calculations were performed using a Hewlett-Packard HP 25. RESULTS

Data for all individuals Data for each fox for the entire observational

period

Total data for the left position for all foxes gives the sum 13 879 with n = 29 030. All foxes were lying on the left side in 47.81% of the observations. The U-test (eq.1) gives 7.47 which is a significant value (p = 0.01).

134 TABLE

II

Data for each fox for each period

No.

1 2 7 8 11 12 13 14 20 22 23 24 25 31 32

6-l (male) (female) (male) (male) (male) (male) (female) (male) (male) (female) (female) (female) (male) (male) (male)

Differences

186 2544 630 62 826 3807 683 417 305 1050 987 887 233 691 571

between

No. of

%X

s

No. of period

U-test

Significance

46.62 46.89 53.68 42.43 35.91 52.22 62.91 47.69 32.91 65.84 41.39 42.66 25.21 47.85 54.51

9.41 11.51 6.80 20.02 5.44 5.90 5.01 2.01 2.84 4.98 4.29 9.23 11.53 5.06 6.61

4 23 6 3 10 20 6 4 4 5 9 6 4 4 4

0.66 2.21 2.84 3.33 12.81 2.49 8.53 1.15 10.19 12.73 8.13 5.39 18.88 1.19 2.94

n.s. 0.05 0.01 0.01 0.001 0.05 0.01

observations 385 5248 1163 167 2261 7400 1085 868 919 1590 2370 2016 1084 1427 1047

Ij:sd1 0.01 0 01 0.01 0.001 Kl

the sexes

If we separate male and female data we obtain the following results Females Males

0 6151 7728

y2309 16721

% 49.97 46.22

U-test 0.06 9.78

significance ,“‘s’ 0.01

The difference between males and females is confirmed by the t-test (eq. 3) with t = 6.33 (p = 0.001). Data for all foxes for different

time-periods

In order to determine the possible factors influencing the decision on resting behaviour (left or right) it is necessary to sum the data for each period for each fox. Data for two individual foxes observations

who were paired for the entire duration

of

During period 6, foxes Nos. 2 (female) and 12 (male) formed a pair and remained as such for the entire duration of observations. Reproduction ensued in the years 1952, 1953 and 1954. As the other foxes were removed from time to time from the observation room, only the behaviour of this pair could be recorded continuously. The data for these foxes (periods 4 to 23) are correlated with the value r = 0.57. Mean values for the left position are as follows: No. 2: 50.10% (minimum 28.10% maximum 64.31%)

TABLE

135

III

Data for each fox

for the entire time of observations

No.of

.n”

fox

No. of period

%

U-test

Significance

1

1 2 3 4

21 39 86 34

79 86 153 67

34.18 45.35 56.21 50.15

2.81 0.86 1.54 0.12

0.01 n.s. n.s. n.s.

2

1 2 3 4 5 6 I 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23

34 40 13 56 50 128 28 77 100 115 172 82 161 83 177 173 182 151 51 100 162 219 130

128 137 178 114 142 270 97 274 282 181 345 144 329 169 310 313 283 249 110 197 307 408 281

26.56 29.20 41.01 49.12 35.21 47.40 28.87 28.10 35.46 63.54 49.86 59.03 48.94 49.11 57.10 55.27 64.31 60.64 46.36 50.76 52.77 53.68 46.26

5.30 4.81 2.40 0.19 3.52 0.85 4.16 7.25 4.88 3.64 0.05 1.67 0.39 0.23 2.50 1.87 4.81 3.36 0.76 0.21 0.97 1.49 1.25

0.01 0.01 0.05 n.s. 0.01 n.s. 0.01 0.01 0.01 0.01 n.s. n.s. n.s. n.s. 0.05 n.s. 0.01 0.01 n.s. n.s. n.s. n.s. n.s.

7

1 2 3 4 5 6

49 91 117 121 108 144

116 162 195 213 183 294

42.24 55.83 60.00 56.80 59.02 48.98

1.67 1.57 2.19 1.99 2.44 0.35

n.s. n.s. 0.01 0.05 0.05

8

1 2 3

17 12 33

26 42 99

65.38 28.57 33.33

1.57 2.78 3.32

n.s. 0.01 0.01

11

4 5 6 9 10 11 12 17 22 23

41 69 99 23 114 160 73 93 65 83

124 186 299 103 292 439 210 217 117 214

37.9 37.1 33.11 22.33 39.04 36.45 34.76 42.86 36.72 38.78

2.69 3.52 5.84 5.62 3.75 5.68 4.42 2.10 3.53 3.28

0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.05 0.01 0.01

12

4 5 6 7 8 9 10 11

112 86 197 120 182 234 177 241

195 209 364 314 431 508 344 457

57.44 41.15 54.12 38.22 42.23 46.06 51.45 52.74

2.08 2.56 1.57 4.18 3.23 1.77 0.54 1.17

0.05 0.05 n.s. 0.01 0.01 n.s. n.s. n.8.

KS.

No.of fox

u-test

No.of period 12 13 14 15 16 17 18 19 20 21 22 23

128 224 98 289 325 248 186 195 209 260 164 132

208 382 207 522 649 478 343 344 417 493 318 217

69.54 58.64 47.34 55.36 50.08 51.88 54.23 56.69 50.12 52.74 51.54 60.83

3.33 3.38 0.76 2.45 0.04 0.82 1.57 2.48 0.05 0.94 0.56 3.19

0.01 0.01 Il..% 0.05

13

5 6 9 10 11 12

33 134 177 86 175 78

52 196 262 155 298 122

63.46 68.37 67.56 55.48 58.72 63.93

1.94 5.14 5.68 1.37 3.01 3.08

0.05 0.01 0.01 ".S. 0.01 0.01

14

6 10 11 12

83 108 179 47

184 217 367 100

45.11 49.77 48.86 47.00

1.33 0.07 0.47 0.60

20

8 9 10 11

15 55 92 143

47 159 313 400

31.91 34.59 29.39 35.75

2.48 3.89 7.29 5.70

0.05 0.01 0.01 0.01

22

13 14 15 16 17

179 125 195 352 199

280 184 283 500 343

63.93 67.93 68.90 70.40 58.02

4.66 4.87 6.36 9.12 2.97

0.01 0.01 0.01 0.01 0.01

23

13 14 15 16 17 18 21 22 23

113 65 142 178 112 108 39 120 110

236 148 310 293 289 279 111 318 277

47.41 43.92 45.81 45.29 38.75 38.71 35.13 37.74 39.71

0.65 1.48 1.48 1.87 3.82 3.77 3.17 4.37 3.42

KS.

13 14 15 16 17 18

151 52 146 216 182 140

340 189 385 425 347 330

44.41 27.51 37.92 50.82 52.85 42.42

2.06 6.18 4.74 0.34 0.91 2.75

15 16 17 18

41 74 52 66

98 378 328 280

41.84 19.58 15.85 23.57

1.62 11.83 12.37 8.84

20 21 22 23

107 223 236 125

222 464 439 302

48.20 48.06 53.76 41.39

0.54 0.48 1.58 2.99

20 21 22 23

85 157 205 124

171 327 346 203

49.71 48.01 59.05 61.08

0.08 0.72 2.86 3.16

24

26

31

32

Significance

ILS. LS. LS.

0.05 n.s. LS. KS.

0.01

ILS. Il..% ILS.

".S.

KS. ll.S.

n.s. 0.01 0.01 0.01 0.01 0.01 0.05 0.01 0.01 Il.?.. ILS.

0.01 KS.

0.001 0.001 0.001 ll.S. Il.S. ILS.

0.01 ILS. KS.

0.01 0.01

137

No. 12: 52.27% (minimum 38.22%, maximum 69.54%) During the three years of continuous data the following correlations between the pair were found: 1952: r = 0.81; 1953: r = 0.55; 1954: r = -0.16. The data for the two foxes exhibits a typical oscillation in the preference for a particular resting position in the course of each year; a relatively high correlation was therefore found. No. 2. 1952153: r = 0.80; 1953154: r = 0.74; 1954155: r = 1.00. No. 12. 1952153: r = 0.57; 1953154: r = 0.64; 1954155: r = 1.00. The higher degree of correlation in the female may be related to breeding behaviour. It must be remarked, however, that for some time after giving birth the female remained inside the breeding box and thus her behaviour could not be observed. Lowest values for the left position were recorded during breeding time, especially in 1952; in the following years the corresponding values remained in the range 40 to 50%. In the years after 1952 the offspring of the previous year were returned to the room some weeks after the new offspring were born. Only in 1952 was the pair alone with its offspring (No. 20) for the entire breeding period. Data for adult foxes

in relation to special conditions

Female No. 13 showed a high negative correlation in her preference for the left position with respect to female No. 2 (r = -0.78). In the mating season of 1953 female No. 13 made several unsuccessful attempts to mate with male No. 12. The “heat” period of the vixen lasts for only 3 days and occurred later in No. 2 than in No. 13. The latter was slightly dominant over No. 2. Male No. 12 was introduced into the group during period 4. The dominant male in this group was No. 7. He preferred the left position with a frequency of 56.8% (p = 0.05). During period 6 male No. 12 paired with female No. 2; he showed a tendency to prefer the left position (54.12% n.s.), whereas in No. 7 (now weakly subdominant) the frequency of left position decreased by about 10%. The values for the left position are extremely low in male No. 11 (33.11%, p = 0.01) during this period; this male was the omega individual within the group (seven foxes). After the breeding season he and female No. 13 were returned to the group (period 9); the male preferred the left position in only 22.33% (p = O.Ol), female No. 13 with her high social status in 67.56% (p = 0.01) of cases. During the following mating season male No. 11 remained extremely subdominant with significant data showing he preferred the right position, whereas female No. 13 showed some variation (Fig.2); her minimum of preference for the left position coincides with the “heat” period of female No. 2. During period 11 the differences in respect to the preferred resting position as evaluated by the G-test according to Woolfe have the following values in certain cases: Male ll/male 20: G = 0.04 n.s.

138

601

50 i

6

7

8

9

10

11

12

13 lh permd

Fig.2. Deviations from the 50% level of the fl resting posture. Abscissa: No. of the period (Table I). Results are shown for female 2. male 12 and female 13.

Male ll/male 14: G = 12.47 (p = 0.01) Male 20/maIe 14: G = 13.36 (p = 0.01) Male 12/male 14: G = 1.28 n.s. Male 12/femaIe 2: G = 0.65 n.s. Female a/female 13: G = 5.07 (p = 0.05) Males Nos. 11 and 20 are extremely subdominant and show a significant preference for the right position: U = 5.7 and 5.68 respectively (p = 0.01). In the next observational period, the mating season, the following relations are worthy of note: : G = 0.74 n.s. Male 12/femaIe 2 : G = 5.79 (p = 0.05) Male 12/maIe 14 Male 14/maIe 11 : G = 4.24 (p = 0.05) Female B/female 13 : G = 0.99 n.s. Male No. 14 was attacked by male No. 12 during the former’s courtship behaviour, which was directed towards female No. 13, and after being overcome only exhibited stereotypes before being removed to another room (Tembrock, 1958a). Data evaluated

with respect to ontogeny

Male No. 20 was reared singly by his parents. This situation is atypical in Vulpes uulpes and lead to a neurotic type of behaviour. He was extremely subdominant. During the five recorded time periods (8-12) he showed a sig-

139

nificant preference for the right position. A developmental trend cannot be demonstrated. In the following year the same pair reared three offspring (females, Nos. 22, 23,24). Their behavioural development was normal. No. 22 exhibited the most rapid development; she alone was reproductive in the next season. The first data following birth were recorded when the three sisters had reached the age of 10 weeks (period 13). The following relations were found: Female 22/female 23: G = 13.46 (p = 0.01) Female 22/female 24: G = 23.69 (p = 0.01) Female 23/female 24: G = 0.68 n.s. The preference for one side was only significant for female No. 22 (a preference of 63.91% for the left position). In the next period (14, age of sisters: 5 months) the dominant female No. 22 shows a significant preference for the left position - 67.93% - and female No. 23 exhibits a weak (but statistically not significant) tendency to prefer the right position; the preference for the right position is significant in female No. 24 (p = 0.01; U = 6.18). The relations are as follows: Female 22/female 23: G = 19.44 (p = 0.01) Female 22/female 24: G = 62.87 (p = 0.001) Female 23/female 24: G = 9.34 (p = 0.01) These relations persisted during the following period. In the early winter the preference for one position was only continued by female No. 22; the difference between females Nos. 23 and 24 disappeared. During the following mating season female No. 22 showed a reduction in her preference for the left position (however, it still remained significant). During all the corresponding observational periods female No. 23 showed a preference for the right position. She was weakly subdominant with regard to her mother (female No. 2). No preference of position was found in the males Nos. 31 and 32 until they had reached the age of 7 months. Initially during period 22 No. 32 showed a significant preference for the left position (59.25%, U = 2.86, p = 0.01); there is, however, no significant difference between the two brothers. In the next period (23) such a difference arises (G = 18.96, p = 0.01). This is also related to the faster development of male No. 32; he alone copulated in the first mating season of his life. He then showed a significant preference for the left position whereas his brother had a significant preference for the right position (p = 0.01). Day- time data In two foxes - Nos. 2 (female) and 12 (male) - we investigated of day with low/high levels of locomotor activity. 09.00-11.00 right position left position

h

No. 2

No. 12

17.00-19.00

93 177

144 233

right position left position

h

No. 2

No. 12

140 61

188 88

two times

140

Statistical analysis for female No. 2 gives the following values: G = 58.42; t = 7.56 (p = 0.01); rtet = -0.53 Preference for one resting position differs significantly between the two times of day; during low activity the fox prefers to lie to the left and vice versa during high activity. The same result is shown by the analysis of the data of male No. 12: G = 58.09; t = 7.55 (p = 0.01); rtet = -0.45 The data for the two foxes summed gives: G = 11.64; t = 10.65 (p = 0.01); rtet = -0.49 The t-test shows no significant differences between the two foxes: 09.00-11.00: t = 0.98; 17.00-19.00: t = 0.36 If we separate the data of the summer from those of the winter a seasonal effect can be shown: h: Female No. 2 right position left position Male No. 12 right position left position

18 December-31 09.00-11.00

March 17.00-19.00

2 June-30 09.00-11.00

August 17.00-19.00

30 103

53 20

63 74

a7 41

70 118

159 70

74 115

29 18

_

_____

Statistical values for “winter data”: Female No. 2 : G = 50.03; t = 7.00 (p = 0.01); rtet = -0.71 Male No. 12 : G = 43.87; t = 6.58 (p = 0.01); rtet = -0.49 The corresponding values for the summer period are: Female No. 2 : G = 13.15; t = 3.61; rtet = -0.35 Male No. 12 : G = 7.74; t = 2.79; rtet = -0.35 The differences between times of day are also significant. Circannual

phenomena

We have previously found seasonal variations of locomotor activity in Vulpes vulpes (Tembrock, 195813, Hilmer and Tembrock, 1972). Vulpes vulpes, V. corsac and Alopex lugopus exhibited the largest yearly changes in daily

activity during the rutting season. In this phase the relation between lightactivity and dark-activity changes. Therefore it is of interest to see if seasonal phenomena occur in regard to the resting position. All foxes The U-values

April-September: 2 = 2.33 s= 1.46 n= 5 October-March : L?= 2.33 s = 0.77 n = 11 The t-test gives no significant differences between the mean values: t = 1.28; to test the variance we use the F-test F = S:/S”,,

S = Sn/(n-1)

: F = 4.09

(p = 0.05)

141

The variance of the U-values during summer differs significantly from the variance of these values during the winter; this may be interpreted as higher functional pressure during the winter (rutting season) with respect to which resting position is preferred. The G-values

April-September: x = 10.23 s = 14.58 n = 20 October-March : iif = 20.05 s = 34.15 n = 80 The t-test of mean values: t = 1.96, c = 0.42, f = 73.59 (p = 0.05) The F-test of the variances: F = 5.28 (p = 0.01) These results indicate that the seasonal differences with respect to the behavioural interdependence of two foxes are significant, with higher values occurring during winter. The pair female No. 2 and male No. 12 April-September

1 No. 2

right position left position

921 664

No. 12

OctoberMarch

1067 1028

No. 2

No. 12

1523 1711

2358 2535

Statistical analysis for No. 2 (female) gives the following: G = 51.80; t = 7.18 (p = 0.01); rtet = 0.17 Preference for resting position differs significantly between the two times of the year. Choice of left position increases significantly during winter. The analysis of the male No. 12 data gives the same result: G = 45.69; t = 6.76 (p = 0.01); rtet = 0.11 For female No. 2 the G-values are also significantly different between the two times of the year:

x s

April-September

October--March

F = 4.37

(p = 0.01)

6.19 6.74

11.53 14.50

t = 1.71

c = 0.39 (P = 0.05)

f= 40.56

The differences with respect to the preferences for resting position in relation to other foxes in winter are significantly higher than in summer. DISCUSSION

The results of the statistical analysis show that in Vulpes uulpes the preferred direction of the resting position (curled up to the right or to the left) is not accidental. For all foxes considered, the preference for the left position is significant, not only for the males (p = 0.01). There are differences between different individuals. No. 1 only exhibits a significant preference in the first time period. He was reared in a human family and hardly developed intraspecific behavioural interactions. Behaviour with respect to the resting position shows periodic changes with temporary significant preferences in

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female No. ‘2. Breeding behaviour in three subsequent years is related to these changes. No. 7 preferred one side of the body in his resting position only temporarily. No. 11 exhibited a preference constant in time. Male No. 12, paired with No. 2, also developed periodic variations. Female No. 13 preferred the left direction, No. 14 showed no preference for one side. No. 20, the first male offspring of Nos. 2 and 12 developed a preference for the right position. The three sisters of the following year (Nos. 22, 23, 24) developed preference tendencies which also applies to Nos. 26, 31 and 32 (the last two are male siblings). These data indicate individual differences in the observed behaviour. Apart from individual dispositions there must be other determining factors for this behaviour. Thus, interactions between the individuals are indicated and as a result variations in the choice of resting position. The data show a correlation between paired foxes (Nos. 2 and 12) with a tendency to decrease during the subsequent years: r = 0.81 in the first year, r = 0.55 in the next and r = -0.16 in the third. This seems to be the result of a phase shift, circumvented by breeding behaviour, which requires activities of the female differing from those of the male. The data for each fox show a high correlation between successive years. Behavioural interactions can be demonstrated by comparing the data of foxes living together. A high negative correlation is found between the two females Nos. 2 and 13 during rutting time (Fig. 2) where r = -0.78 whereas the pair (Nos. 2 and 12) show a high positive correlation (r = 0.76) with regard to the choice of the preferred side in the resting position. During “heat” female No. 2 was dominant over female No. 13; only during this time was her preference value for the left position higher than for female No. 13; the maximum of No. 2 coincided with the minimum of No. 13. This can be interpreted as a result of their highly agonistic behaviour in this phase. These results lead one to the hypothesis that dominance value is positively correlated with a preference for the left position. Males Nos. 11 and 20 are extremely subdominant, both individuals developing a high preference for resting positions to the right, the left side of the body being then oriented towards the substrate. Male No. 12 exhibited significant differences in his resting positions with regard to the other males in the rutting season; he was the alpha fox. The behavioural ontogeny of male No. 20 (who had no sisters) led to extremely subdominant behaviour. This fox had only his parents for play purposes and was always the &weakerpartner. As a result he exhibited social inhibitions. The three females born in 1953 developed first tendencies to prefer one side in resting position, but only significantly in one female (No. 22). She alone exhibited sexual activity with copulation in the next rutting season. This fast development was correlated with a dominant status with respect to her sisters and also a preference for the left resting position. Indeed the preferences begin with the establishment of an order of rank within the ontogeny. The degree of sexual maturity will be the dominating factor. Besides the bio-social interactions, the time of day and of year are also factors influencing resting position. Bio-social behaviour, however, undergoes circadian and circannual fluctuations. The fox pair which was tested with

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respect to circadian phenomena displayed no dominance behaviour during the period in which data were collected. Nos. 2 and 12 lived together with their offspring of the previous year: hierarchical behaviour in adult foxes is inhibited under these conditions. Thus, at the time of day when a high level of locomotor activity prevails (1’7.00-19.00 h) the right resting position dominates; during low activity (09.00-11.00 h) the left position is prevalent. Differences between the two times of day are significant. The left position indicates the social status which is inhibited during the phase of activity (and social contacts) from the age of 9 months. These circadian variations also continued during the summer months but with decreasing differences of magnitude. The hormonal state of Vulpes uulpes undergoes a circannual variation. Under natural conditions bio-social interactions between adult foxes are only exhibited in the winter, especially during rutting time. Therefore we have to expect in this phase the most pronounced expression of territorial and order of rank behaviour and, as ‘a result, the maximal values of differences in the choice of direction in resting position. Our data confirm these assumptions. If we take all data together the main value does not differ significantly between summer and winter; this, however, results from the fact that both young and older individuals are included in our material. We have to take into consideration that under our laboratory conditions the foxes were also kept together during the summer. Apart from this, the variance shows significant differences between summer and winter. This means that during the winter the significantly lower variance results from the increasingly determined agonistic behaviour, the social status being fixed. The U-values show a significantly lower variance. This appears to express a circannual rhythm. With respect to the G-values (relations between two animals) the mean values differ significantly between summer and winter. This verified the assumption of an influence of the bio-social status on choice of body position of foxes when resting. Considering the phenomena observed, it seems that our foxes are forced to develop behavioural patterns of dominance and subordination in the management conditions in which they were kept, whereas under natural conditions males show agonistic behaviour with patterns of dominance and subdominance only during the rutting season. In this sense, the behavioural peculiarities observed are “artefacts”. Nevertheless, there are systematic influences, caused by the interactions between the foxes. We presume that lying on the left side of the body warrants a higher arousal and therefore a shortening of reaction time and this appears to be advantageous to subdominant individuals.

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