Vulpes Vulpes in the Ashio Mountains, Central Japan

J. Mamm. Soc. Japan 17(2) : 95-110 October 1992

Home Range and Habitat Utilisation of the Red Fox Vulpes vulpes in the Ashio Mountains, Central Japan

Masahiko TAKEUCHI and Masaaki KOGANEZAWA*

Biological Laboratory, Faculty of Education, Ibaraki University, Mito 310, Japan (Present address : Ecological Laboratory, Graduate School of Natural Science and Technology, Kanazawa University, Kakuma Kanazawa 920-11, Japan) * Tochigi Prefectural Museum, Utsunomiya 320, Japan (Present address : Utsunomiya University Forests, Funyu 7556 Shioya, Tochigi 329 -24, Japan) (Accepted 18 May 1992)

Abstract. One female and three male red foxes Vulpes vulpes were radio- tracked between November 1988 and September 1989. The sizes of their home ranges were calculated using the harmonic mean and three other methods. The size of the female's range and her core area changed with her reproductive stages. She maintained her largest range (601.2 ha as a harmonic mean), with two core areas (196.4 ha), during the pre-breeding period. Her range decreased with the advance of her pregnancy, and was smallest (108.7 ha) during the denning period, during which her out-of-den activities were confined almost exclusively to a small circum-den area. Her range increased again during the post-denning period. The summer ranges of the males were larger (582.5 ha on average) than the post-parturition range of the female, and their range sizes remained relatively constant. The female occupied mainly a riverside area, whereas the males tended to range extensively over inter-river areas. Bon- ferroni 2-tests showed that grasslands and riversides were preferred for foraging and resting by both sexes, whereas forests and steep slopes were avoided during most periods. Craggy slopes were utilised mainly for resting. A scatological analysis suggested that the foxes depended for a large proportion of their food on the Japanese field vole Microtus montebelli.

Key words : Red fox ; Radiotelemetry ; Home range ; Habitat preference ; Activity rhythm.

The home ranges of the red fox Vulpes vulpes L. have been studied using radiotelemetry since the 1960s, mainly in North America (Ables, 1969), England (Macdonald, 1980), and Europe (von Schantz, 1981). The sizes of home ranges and ecological factors determining range sizes were compared between Eng- land and Canada (Voigt & Macdonald, 1984). Home ranges of the Japanese red fox have also been studied in Hokkaido, northern Japan (Misawa et al., 1987), and in Kyushu, southern Japan (Eguchi et al., 1977), although data are still fragmentary. In these studies, range sizes were estimated by conventional methods such as the convex polygon method and the bivariate normal ellipse. Recently, 96 Takeuchi & Koganezawa however, the harmonic mean method has been developed to describe not only quantitative but also qualitative aspects of ranges (Dixon & Chapman, 1980). Woollard and Harris (1990) applied this method to their fox study dealing with dispersal and home range, however, theirs was a relatively short-term study which it did not address the changes of range parameters in relation to the reproductive stage. The present report describes both the reproductive stage and the seasonal changes observed in the sizes and utilisation patterns of home ranges of red foxes i1;1 Central Japan. The harmonic mean method was applied to the data obtained from a population inhabiting a temperate mountainous area consisting of forests, craggy slopes, and grassland. In addition, habitat preferences were analysed with respect to topographic and vegetational conditions.

Materials and Methods

Study Site Our study was conducted between November 1988 and September 1989 in the eastern part of the Ashio Mountains (139.4" E, 36.6" N) at altitudes ranging from 700 to 1500 m above sea level. The boundaries of the study area (5X4.8 km) were established so as to include the most widespread radio-telemetric locations, and the study area was meshed with l-ha grid and divided into 2400 cells on a 1 : 25,000-scale topographic map. Habitats were classified into four general types according to vegetation and topographic features (Fig. 1) : 1) level grassland with Miscanthus and Polygonurn ground cover, 2) sandy riverside sparsely covered with Equisetum, 3) craggy slopes on which Athyrium ferns grew sparsely, and 4) forest, mostly broad-leaved deciduous, consisting mainly of Clethra and Alnus. Slope inclinations ( 30") and aspects of slopes (N/NW, E/NE, S/SE, and W/SW) were found for each grid sector from the map.

Trapping and Radio - tracking One female and three male foxes were caught with padded gin traps (Victor Soft CatchTM,Wood stream Co., USA) between November 1988 and May 1989. They were immobilised with an intramuscular injection of 1.5 ml of a 2:l volume mixture of ketamine hydrochloride (50 mg/ml)- atoropine sulfate (50 mg/ml). The animals were equipped with radio-collars approximately 110 g in weight, set at 146 MHz with potential working lives of from six to 24 months. Standard body parameters were recorded, and ages were determined by means of the sequence of eruption of permanent teeth (Sasakawa, 1984) and the annual attrition of incisors (Harris, 1978). The foxes were each tracked for from one to eight months. At least three 8-hr tracking sessions and one 24-hr session were conducted monthly by vehicle and on foot. Locations were recorded every hour using a hand recei-ver with a 3-element hand-held Yagi antenna. Linear distances between locations were measured as moving distances per hour. One of the transmitters was modified Home Range and Habitat Use of Red Fox

Grassy level land

Sandy river side

...... Craggy s l ope ......

Forest

Fig. 1. The study site showing the four main types of vegetational and topographic features. Mountain ridges are shown with heavy dashed lines, peaks with triangles, and streams with thin lines. Human residential areas are shown with the black rectangles. to be motion-sensitive so as to facilitate the recording of the animal's move- ment (ATS Co., USA). Determination of activities was based on the relationship between the relative time in motion and the distance moved per hour. The animals were regarded as "active" when they moved more than 100 m per hour, and "resting" when moving less than 100 m/hr. Each location point was later plotted on a topographic map (scale 1:25,000) and allocated to a l-ha grid cell. The relative amount of den use, by the female, was calculated from continuous data records during the denning period. Departures from and arrivals at the den were easily identified when using a receiver set on the opposite side of the river, by the sudden changes of the signal' level.

Range-size Calculations Home range sizes were calculated with a computer program, "HOME RANGE, ver. 2.00" (Ackerman et al., 1990), using the harmonic mean estimator (Dixon & Chapman, 1980). This program also identifies core areas by comparing the utilisation distributions from the harmonic mean calculations with a uniform use model (Samuel et al., 1985). The core area represents the central .area of consistent or intense use (Kaufmann, 1962), and is defined here as the maximum area where the observed utilisation distribution (based on harmonic values) exceeds a uniform utilisation distribution (Samuel et al., 1985). Har- monic mean core areas were used to compare the shape and spatial utilisation of the home ranges. To compare the present results with those of previous studies, we also estimated the range sizes using the bivariate normal ellipse (Jennrich & Turner, 1969), and loo%, and 95% minimum convex polygon 98 Takeuchi & Koganezawa Table 1. Parameters of four red foxes studied Weights Period of No. of Names Sexes Ages (kg) radio-trackings fixes

SC P s.a.l1 4.7 Nov. 22 '88 - Aug. 8 '89 536 DR d' s.a. 5.1 Feb. 16 '89 - Sep. 1 '89 278

MS C? 1 4.4 May 13 '89 - Sep. 1 '89 118 BP d' 2+ 5.9 May 14 '89 - Jun. 11 '89 29

' 1) s.a. : Estimated to be sub-adult (between 6-months and I-year old). methods (Michener, 1979).

Results

Histoyy and Breeding Cycle of the Study Animals The captured foxes were named SC?, DRd, MSd, and BPd (Table 1). The age of BPd was determined as 2+ years, while all of the other animals were considered to have been born in the previous spring. The animals were radio-tracked from the date of their capture; tracking of SC? ended, due to battery failure, on 8 August 1989; tracking of DRd and MSd continued until the end of the study on 1 September 1989. BPd was tracked until the death of him, on 11 June 1989, and data from it were only partially incorporated into the analysis because they were generally insufficient. Since the size and utilisation patterns of SCP's home range were affected primarily by breeding activities, her reproductive stage was divided into four periods: 1) "Pb" Pre-breeding period from November (start of observation) to the end of January, 2) "Pg" Pregnancy period, estimated at 53 days (Lloyd, 1980)' from the end of January to mid-March, 3) "Dn" Denning period (parturition, suckling, and bringing solid food), about 60 days from mid-March to the mid-May, and 4) "Pd" Post-denning period, about 80 days from mid-May to early August (last observation). It was difficult to divide male stages into distinct periods, but they were tentatively divided into just spring (March- May) and summer (June- August) periods. The summer period corresponded approximately to the female's Pd.

Sizes of Home Ranges and Core Areas The home range size of SC P,represented by the harmonic mean, changed considerably throughout the reproductive stage (Table 2). It was largest (601.2 ha) during Pb, and decreasing gradually, it attained its smallest size (108.7 ha) during Dn (Figs. 2A, B, and C) followed by a slight increase again during Pd (Fig. 2D). During Pb, the core area (consisting of a large area and a small satellite area) was of 196.4 ha (Table 2, Fig. 2A). During Pg, the satellite area disappeared, and the main area shrank to half its previous the size (Fig. ZB), and the minimum core area (20.5 ha) was attained during Dn. Home Range and Habitat Use of Red Fox ' 99 Table 2. Home range sizes and harmonic core areas of one female and two male red foxes in the Ashio Mountains, calculated by three different methods Home range and core area sizes (ha) Names No. Bivariate normal Convex and Periods Harmonic means of fixes ellipses polygons sexes 95% Core 95% f SE 100% 95% SCP Pb (Pre-breeding) 191 (2)l) 601.2 196.4 494.3 + 36.0 519.5 390.0 Pg (Pregnancy) 142 (8) 230.3 100.4 320.1 + 27.1 310.0 198.5 Dn (Denning) 110 (7) 108.7 20.5 165.5 f 15.9 146.5 95.5 Pd (Post-denning) 94 (9) 171.1 46.8 305.0 f 31.8 248.0 173.5

DR8 Spring Summer MS8 Summer 1) Numerals in parentheses refer to points omitted from harmonic mean calculations as outliers.

Fig. 2. Shapes, locations, core areas, and utilisation patterns of the home range of SC? during four consecutive reproductive stages in the Ashio Mountains. A-D : Home ranges show 95% harmonic mean contours (outer heavy black lines), 95% bivariate normal ellipses (dot-dashed boundaries), and 100% convex polygons (light lines connecting squares), harmonic core areas (inner heavy black lines), harmonic activity centres (triangles), outlying location points (squares), natal den (circle ; C only), rivers (thin black lines and-mountain ridges (heavy dashed lines) ; E-H : 3-dimensional utilisation distributions of the home ranges. 100 Takeuchi & Koganezawa The spring range of DR3 was 377.8 ha (Table 2, Fig. 3A), and grew to 613.9 ha during summer, when it was 1.6 times larger than in the spring (Fig. 3B). DRa's core area also increased in size during the summer to 1.8 times more than in the spring. MSa had a main range (524.6 ha) and two smaller ranges (26.0 and 0.4 ha), with a combined core area of 194 ha during the summer (Fig. 3C). The home ranges of the males were about 3.4 times larger than SCq's range during Pd. Range areas calculated by the bivariate normal ellipse and the normal convex polygon methods (see Table 2) were up to 1.8 times larger than by the harmonic means, whereas values of the 95% convex polygon tended to be smaller (Table 2).

Utilisation Patterns of Home Ranges and Core Areas The shape of ranges and their utilisation patterns were examined on the 95% harmonic mean and core areas (Figs. 2 and 3). During Pb, SCP's home range extended more in a north-south direction than in an east-west direction, and the centre of activity was focussed to the south of the main part of the core area (grassland) (Figs. 1 and 2A). With the subsequent reduction of the size of the home range, the centre of activity shifted closer to the centre of the home range, that is to the riverside area (Fig. 2B). The fundamental pattern of utilisation, however, did not change through these two periods, during which she used the core area quite evenly (Figs. 2E and F). After giving birth to cubs on 17 March, she stayed in the natal den for almost a week. As Pg progressed into Dn, SCP's range became further reduced in size, and its shape was trans- formed so that it resembled a gourd, with the centre of activity close to the natal den (Figs. 2C and G). On 21 April she abandoned the natal den and moved her cubs to a second den about 300 m away, which she used until 17 May. During Dn, she occasionally travelled to a human residential area situated at the southern corner of the convex polygon as she had during previous periods. She visited this area more frequently during Pd, and shifted her home range as a whole, to the south during this period (Fig. 2D). The distribution and utilisation of core areas were similar during these periods, although they were distinguishable from those during Pb and Pg (Figs. 2E and F), by their greatly concentrated use of smaller areas (Figs. 2G and H). During the spring DR3 occupied a triangular-shaped range with a single core area, with a small projection at the north-east corner, and an activity centre in the middle (Fig. 3A). During the summer, the western part of DR3's home range became extended, and the activity centre moved slightly to the north-west, though it still remained within the spring core area. DR3 mainly used the larger part of the core area at an altitude of 800 m, but also visited the extended area at a higher altitude (1200 m) by crossing over a ridge lying between these two parts of his range (Figs. 3B and E). Several cubs were seen at two different sites in DR's home range (Fig. 3B), however, he- was not observed visiting the den, nor did he bring food to the cubs or the female. MS3 occupied a home range consisting of one main and two extremely Home Range and Habitat Use of Red Fox ' 101

Fig. 3. Shapes, locations, core areas, and utilisation patterns of the home range of DR2 and MS2 during spring and summer periods in the Ashio Mountains. A-C : Home ranges show 95% harmonic mean contours (outer heavy black lines), 95% bivariate normal ellipses (dot- dashed boundaries), and 100% convex polygons (light lines connecting squares), harmonic core areas (inner heavy black lines), harmonic activity centres (triangles), outlying location points (squares), points at which cubs were observed (circles ; B only), rivers (thin black lines) and mountain ridges (heavy dashed lines) ; D-F : 3-dimensional utilisation distributions of the home ranges. small areas. The main range had a boomerang-shaped core area straddling a mountain ridge, with an activity centre at its inflection (Fig. 3C). Both DRG and MSG used their ranges and core areas more evenly than did SC?. BPG received an injury to his left foreleg when being trapped on 14 May 1989, thereafter he occupied only a small range during May and June, possibly as a result of this injury (Fig. 4A). Meanwhile, DRGand MSG occupied ranges adjacent to, and partially overlapping, the western border of BP's range (Fig. 4A), however, they did not invade BP's range, even after his subsequent death on 11 June. In July, however, both DRG and MSG occasionally visited outlying points within the former range of BPG, and thus extended their own ranges to include parts of BP's range (Fig. 4B). The ranges of DRG and MSG were generally separated by a large river, although there was some-overlap, with MSG possessing small satellite ranges within DR's range in summer. Their core areas, however, did not overlap. 102 Takeuchi & Koganezawa

Fig. 4 Spatial distribution of home ranges of the two younger males, DR (heavy lines) and MS (thin lines), until the death of the older male, BP (dashed lines), (A) and after his death (B). Home ranges show the 95% harmonic mean contours (outer round lines), harmonic core areas (inner round lines ; B only), harmonic activity centres (triangles ; B only), 100% convex polygons, rivers (thin black lines) and mountain ridges (heavy dashed lines).

Activity Patterns Using location data points collected for three foxes, we were able to determine distances moved per hour and thus able to calculate daily distances moved. The daily activity rhythms of the female and of two males during different periods are shown in Fig. 5. SCP's rhythms were constant throughout the periods except during Dn, all being monomodal with a peak of activity at night between 17:OO and 22:OO hr and a period of inactivity (100-300 m/hr) during the daytime from 06:OO to 16:OO hr. Out-of-den activities were extremely low during Dn, especially in the early half, during which she left the den only a few times at night. Thus, this period was regarded as one of general inactivity. Continuous recording over a 60-hr period in mid-April showed that SCP stayed in the den for more than 80% of the time; she made 14 trips, of which four were only momentary and five of which were long trips exceeding 1hr, presum- ably for foraging (Fig. 6). Average distances moved per hour (based on values for both "active" and "resting") changed throughout the periods, with a minimum value during Dn (Table 3). When average distances moved were calculated on "active" values, the results varied from 434 to 581 m/hr throughout the periods, without any extreme drops during any period (Table 3). Daily activity rhythms of the two males were constant, irrespective of the period, and were similar to those of SCP (Fig. 5). The average distances moved were similar (about 530 m/hr, values for "active") in both spring and summer, and the maximum distances moved exceeded those of the female (Table 3). Home Range and Habitat Use of Red Fox

Time in hours

Fig. 5. Daily activity rhythms of the female (SC) and the male (DR and MS) foxes. Solid line indicates the activity rhythm of SC P from the pre-breeding to the post-denning periods, except in the early stages of the denning period (indicated by dashed lines). Dotted line shows that of DRd and MSd, in spring and summer.

...... ::::::::::::...... Out-of-den activities

in-den activities

I I Momentary departure (1-2 min.) from den

Fig. 6. A chronological record of the out-of-den and in-den activities of SC? over a continuous period of 60 hrs from 18 to 21 April 1989. 104 Takeuchi & Koganezawa In conclusion, the foxes in our study area were nocturnal and had monomodal daily activity rhythms regardless of their sex. The female's activity levels varied considerably according to her reproductive stage, whereas they were almost constant in the males, at least during spring and summer.

Habitat Preference Habitat preferences were analysed with the Bonferroni 2-test once significant differences had been detected with the x2-test (White & Garrott, 1990). Computer-generated random samples as expected values of habitat points were selected from grid samples following Marcum and Loftsgaarden (1980). The test was made for two different expected values, one of which was for the entire study area, and the other for the 95% harmonic mean for each individual and each period. The former showed preferences by the foxes for local environ- mental-conditions, and the latter revealed patterns of individual utilisation within each animal's own range. Since the utilisation pattern was expected to differ at different activity levels, the test was done also for both "active" and "resting". In tests for the entire area combining "active" and "resting" (Table 4), all of the study foxes tended to use certain types of cover and clearly avoided forests. SCP and DR3 preferred grasslands during all periods. SCP also preferred sandy riversides during Pb and Pg, and craggy slopes during Pg. When tested for 95% harmonic mean home range, a similar result was obtained. SCP and DRg used particular types of cover, whereas MS3 used cover types evenly. SCP preferred grasslands and riversides during Pb and selected the former for a denning site. She avoided forests only during Pb and craggy slopes during Dn. DR3 only avoided the forests during the summer. Tests for the entire area, conducted separately for "active" and "resting",

Table 3. Changes in the average distances moved per hour (A.D.M.: m/hr) throughout the reproductive stage, calculated on all values ("active" + "resting") and on "active" values alone, and maximum distances moved (Maximum D.M.: m/hr) during each period A.D.M. on A.D.M. on Maximum Periods nl) nl) all (SD) "active" (SD) D.M. Female Pb (Pre-breeding) 111 441.6 (369.6) 95 509.3 (357.3) 1700 Pg (Pregnancy) 122 365.7 (357.5)] 101 434.1 (356.3) 1688 Dn (Denning) 77 298.5 (460.3) *2) 39 581.4 (505.6) 1975 Pd (Post-denning) 73 414.0 (474.2) 56 532.3 (482.4) 1800 Males Spring 91 389.0 (558.1) 64 535.3 (608.4) 3325 Summer 206 339.8 (454.9) 130 526.2 (483.0) 2750 1) n : Numbers of samples calculated. 2) * : Significant with period Pb at p < 0.05 level (2 tailed t-test). Home Range and Habitat Use of Red Fox 105

Table 4. Cover preferences of the female (SC) and two males (DR and MS), tested with "active" and "resting" combined

Names Periods No. Sig. Habitat attributes and of levels1) Grass- River- Craggy Forest sexes fixes E/I land side slope SCP Pb (Pre-breeding) 191 * * * / * * * P/pz) P/p / A/a Pg (Pregnancy) 128 ***/ ** P/ P/ P/ A/ Dn (Denning) 110 ***/ *** p/P / /a A/ Pd (Post-denning) 94 / ** p/ / / A/

DRd Spring Summer MSd Summer 1) Categories of expected values. Entire study area (E) and 95% harmonic mean home range of individual (I). * * * , * * , * and ns: x'-test significance level at p <0.001, <0.01, < 0.05, and non-significant, respectively. 2) P and p: preferred, A and a: avoided and blanks: non-significant for expected value (Bonferroni Z-test). Capital letters indicate results for E and small letters for I. gave basically similar results for each, although there were some differences (Table 5). During the pre-parturition period (Pb+Pg), SC preferred grasslands in which to be "active", whereas she preferred craggy slopes for "resting". Forests were neither avoided nor preferred, except by MSa who used them for "resting". In tests for 95% harmonic mean estimates, SCP neither preferred nor avoided grasslands and riversides for being "active", whereas she preferred the former and avoided the latter for "resting" during the post-parturition period (Dn+ Pd). In spring, DR3 avoided forests for "resting", but not for being "active". The three animals preferred flat and gentle slopes (less than 10") virtually throughout the study period, and all avoided slopes steeper than 30". SC? selected gentle north-facing slopes far her denning site, and used intensively south-east facing craggy slopes for resting, until parturition. When tested for "active" and "resting" combined, the two males used any slope regardless of its aspect. Separate tests showed, however, that all foxes avoided sunny east facing slopes for "resting" during summer (the post-parturition period for the female), probably because they would be uncomfortably hot for resting at that season.

Discussion

Home Range The home range size of the red fox varies widely from approximately 10 ha in urban areas (Harris, 1980) and rich farm lands (Lloyd, 1980), to 3400 ha in 106 Takeuchi & Koganezawa

Table 5. Cover preferences of the female (SC) and two males (DR and MS) tested separately for "active" and "resting"

No. Sig. Habitat attributes Names Periods Activity of levels') and Grass- River- Craggy Forest sexes types fixes E/I land side slope

SCP Pre-parturition "Act" 203 * * * / * * * P/p /P A/a (Pb + Pgy) "Rest" 35 * * * / * * * / / P/ A/a , Post-Parturition "Act" 96 * * * / * * P/ / 1 A/ (Dn + Pd) "Rest" 55 * * * / * * * P/p /a / A/

DR3 Spring 6L~Ctpp52 * * * / * * / / / A/ . "Rest" 24 * * * / * * / / / A/a Summer "Act" 85 * * * / * * P/ / 1 A/ "Rest" 31 * * * / * * P/ / / A/ MS3 Summer "Act" 40 * ** / / / A/ "Rest" 42 NS/ ns / / / / 1) Categories of expected values. Entire study area (E) and 95% harmonic mean home range (I). * * *, * *, * and NS (ns) : x2-test significance level at p <0.001, <0.01, <0.05, and non-significant, respectively. 2) Female's breeding periods. Abbreviations : Pb, Pre-breeding ; Pg, Pregnancy ; Dn, Den- ning ; Pd, Post-denning. 3) P and p : preferred, A and a : avoided, and blanks : non-significant for expected value (Bonferroni 2-test). Capital letters indicate results for E and small letters for I.

Arctic regions (Sargeant et al., 1987). Our results (653 ha ; 100% convex polygon) from the Ashio Mountains of Japan are comparable to those of the Swedish taiga (510-690 ha ; LindstriSm, 1989), and the ranges fall within the middle-sized category of Jones and Theberge (1982). Elsewhere in Japan authors have estimated red fox home range sizes as 81 ha in Kumamoto Prefecture, Kyushu (Eguchi et al., 1977) and 546-818 ha in Hokkaido (Misawa et al., 1987) based on short surveys ranging from several days to one month. These values, however, are unlikely to represent true home range sizes due to improper operation of radio-tracking equipment and insufficient location points. A comparison of values taken from'various localities suggests that the estimates from the present study represent the average size realized in mountainous areas of the temperate zone, where food resources are not particularly ample. In comparing the range sizes estimated in the city of Oxford, England (45 ha), and the Canadian province of Ontario (900 ha), Voigt and Macdonald (1984) concluded that range size differences probably resulted from different levels of food availability. Considerable changes in the ranges of females in relationship ta breeding activities (as seen in the present survey) have also been reported previously (Lloyd, 1980; Macdonald, 1980), however, previous studies dealt only with Home Range and Habitat Use of Red Fox 107 changes of size estimated by conventional methods. The harmonic mean parameters of range and core area offer information indispensable for learning utilisation patterns. Female SC, for example, reduced the size of her range with the advance of her reproductive stage (Figs. 2E and F), and concentrated her activities on an extremely limited area during Dn (as indicated by the 3- dimensional graph, Fig. 2G). The two males, however, maintained their use of large ranges, at least from March to August (Figs. 3D, E, and F). Separation of the core area in a single range into two or three parts suggests that the individual has several active centres used for various purposes. For, example, SC? seemed to use the main core area for nursing her cubs, for foraging and other minor purposes during Dn, and another small area in the northern part for resting (Fig. 2D). The patterns of occupation differed noticeably between the two sexes in this study, that is, SCP's range lay along the river, whereas the males' ranges were extensive in inter-river areas involving ridges. With such a small sample size we do not know, however, whether such a difference was the result of sexual or individual preference. The distribution of the three male ranges suggests that BP the oldest male had defended his range most vigourously until being injured, and was still able ta exert some influence over the younger males even after the accident. BP's range, including riverside areas, was regarded as good habitat supplying ample food. It took more than one month for his successor(s) to fully occupy such a good range after BP's death. Woollard and Harris (1990) stated that in urban areas the replacement of occupants occurred rapidly. Although it is difficult to explain the difference between mountain and urban cases, one reason may be social interactions (competition for resources) occurring between two males or among more males including some perhaps unobserved during our survey.

Habitat Utilisation Foxes were found, in this study, frequently to visit grasslands and riversides. A preliminary result of fecal analysis made in these areas suggests that the Japanese field vole Microtus montebelli Milne-Edwards was a main source of food for foxes during all seasons (Takeuchi, unpubl.). The foxes preferred these places, probably because their prey lived there in large numbers (Inui, unpubl.). By contrast, in the forested areas rather than field voles, the Japanese field mouse Apodemus speciosus Temminck and the Japanese wood mouse A. argenteus Temminck were found to predominate, as in other mountainous forests of Honshu (Kitahara, 1986). Although densities of Apodemus mice were high in the forests surveyed (Inui, unpubl.), foxes apparently avoided or could not catch them as evidenced by the virtual lack of Apodemus bones in their feces. In other districts, foxes have also been found to choose more Microtus and Clethrionomys voles than Apodemus mice (Korschgen, 1959; Fairley, 1970; Doncaster et al., 1990). In Hokkaido, the red fox mainly feeds on large red-backed voles Clethrionomys rufocanus Sundevall on open meadows (Yoneda, 1982). These facts are consistent with the current observations. 108 Takeuchi & Koganezawa What is the reason for foxes to be so dependent on voles, rather than on mice? Two points seem to be relevant with this question. First, Microtine voles live in confined areas surrounding their nests (Watanabe, 1962), and the clumped distribution of vole nests at relatively high densities (Kitahara, 1980) makes the predictability of their occurrence as potential food greater than that of mice around mouse nests. Second, voles are gene.rally less agile than mice (Watanabe, 1962), making it easier for foxes to catch them than mice ; they are thus more vulnerable as prey for foxes (Cook & Hamilton, 1944). Furthermore, in Europe and North America, leporids, especially rabbits, in addition to voles, have been found to be a principal food source of the red fox (Cook & Hamilton, 1944 ; Englund, 1965 ; von Schantz, 1980). European rabbits Oryctolagus cuniculus L. usually live around their warrens (Kolb, 1991), as do voles around their nests, and do not make distant trips, whereas hares are fast, agile and make long distance movements. Differences in styles of locomo- tion between rabbits and hares (Schnurr & Thomas, 1984) and in certain aspects of their life patterns mean that rabbits, like voles, are easier prey for foxes than hares. Although the Japanese hare Lepus brachyurus Temminck is common in Honshu and the arctic hare L. timidus is widespread in Hokkaido, foxes have only rarely been found to hunt hares in our study area. Japan has only one species of rabbit, the Amami rabbit Pentalagus furnessi Stone, and this is endemic to Amami-Oshima and Tokunoshima (islands in southern Japan), where there are no foxes. These facts lead to the conclusion that the distribution patterns of prey species largely affect the patterns of range utilisation of foxes. In our case, grasslands and riversides seemed to be preferred, at least partially, due to ample food supplies there, whereas forests were avoided for the opposite reason. Elsewhere, however, the red fox has been found to hunt Japanese hares, in the deep snowy areas of the South Japan Alps for example (Torii, 1989), and a fecal study in Ashio indicates that the foxes there also feed on the dead bodies of sika deer Cervus nippon Temminck found during early spring. More extensive and more detailed studies are required therefore to more fully elucidate the relationship between range utilisation and food distribution in the red fox in Japan.

Acknowledgments

We thank Dr. S. Yamane, of Ibaraki University, for his encouragement during the course of this study. Dr. S. Yamane, Dr. D. W. Macdonald, of the University of Oxford, Dr. H. Abe, of the Hokkaido University, and Mr. T. Nakazono, of the Soyoh High School, critically read the manuscript. Prof. M. Suzuki, of Ibaraki University, identified some plants collected in the field; Dr. H. Higuchi, of Tochigi Prefectural Museum, supported our survey in various ways, and Mr. T. Inui of the museum offered us his unpublished data. Dr. H. Higashi and the staff of the Wildlife Management Office cooperated in capturing the animals and Prof. M. Niizuma, of Ibaraki University, allowed us Home Range and Habitat Use of Red Fox 109 the use of a micro-computer for calculations. This work was supported in part by the Tochigi Prefectural Museum.

References

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