Vol. 7 11998): 21 Seasonal and circadian changes in activity rates of adult farm blue foxes Hannu Korhonen, Paavo Niemelä Agricultural Research Centre ofFinland, Animal Production Research, Fur Animal Husbandry, FIN-69100 Kannus, Finland, e-mail: hannu.t.korhonen@mtt.fi The present paper reports systematic activity rates obtained from year-round video recordings of farmbred blue foxes (Alopex lagopus) housed singly in conventional wire-mesh cages (107 cm wide x 110 long x 70 cm high). Subjects were 9 males and 13 females. Mean whole-year activity rates were slightly higher in males (394 ±ll6 min/24 h; mean ± SD) than females (349 ±lll min/24 h). Significant (P<0.001) seasonal variations were found in the activity rate of both sexes. Females were most active in May (539 ± 157 min/24 h) and males in June (471 ± 128 min/24 h). Lowest activity rates were in September. Activity rates of males, in particular, tended to increase at the approach of the breeding season in March. Seasonal activity patterns of farmed foxes resembled that of foxes living in the wild. Circadian activity was concentrated on farm work hours (0800-1600) in winter, but not in summer. Typically farmed blue foxes were most active between sunrise and sunset. Diurnal pattern of farmed foxes is markedly different to wild foxes which typically exhibit a more nocturnal pattern of activity. Key words: behaviour, daily active time, farm foxes, fur farming, yearly variations ntroduction The farm-life history of the blue fox, a colour mutation of the arctic fox (Alopex lagopus), is over 70 years old. However, there still exists a lack of systematic knowledge on many behav- ioural traits of this species in captivity. For in- stance, rate and pattern of their activity requires more clarification. Comparisons between captive and wild conditions are particularly scarce. The need for more comprehensive data has emerged when attempting to develop housing environment for farmed foxes towards a more functional and natural direction (Braastad 1992, Bakken et al. 1994, Harri et al. 1995, Jeppesen 1996). The classic study on captive foxes’ activity and behaviour was conducted with two arctic foxes housed in a ground enclosure throughout the year (Tembrock 1958). The foxes in that © Agricultural and Food Science in Finland Manuscript received August 1997 21 AGRICULTURAL AND FOOD SCIENCE IN FINLAND Korhonen, H. & Niemelä, P. Activity rates offarm bluefoxes study exhibited seasonal variations in activity rate with highest levels occuring at the onset of the breeding season and lowest ones during au- tumn. Much later, Korhonen and Alasuutari (1994, 1995) documented occasional observa- tions on the behavioural activity ofgroup-housed arctic blue foxes in ground enclosures withpar- allel results. As concerns the actual fur farm con- ditions, Korhonen (1988) conducted visual ob- servations on the seasonal activity rates of five male blue foxes kept in conventional wire-mesh cages under a shed. Activity rates of these foxes also showed year-round variations, being most pronounced in summer. Furthermore, video re- cordings on the breeding activity of farmbred blue foxes have demonstrated that activity rates increase from January to March (Korhonen and Niemelä 1995). Thus, there exists evidence that farmed blue foxes obviously exhibit annual var- iations in activity rates. Recently, Mononen et al. (1996) and Rekilä et al. (1996) presented some additional activity data derivedfrom short- term video recordings made during one month. Their results suggest that the activity offarm blue foxes follows a clear circadianrhythm, with fox- es being most active during work time (0800- 1600). Korhonen (1988) previously reported observational data which also indicated that cir- cadian activity of farm blue foxes often concen- trates on daylight hours and work times. The re- sults ofTembrock (1958) also revealed a distinct relationship between activity and circadian light rhythm. In that study arctic foxes were least ac- tive between 1000 and 1600. In conclusion, there are several short-term studies which have report- ed activity patterns of foxes in captivity, but there is still a lack of systematic information from whole-year recordings. The objective of the present behavioural study was to provide more comprehensive data on activity patterns of blue foxes under typical cage conditions. Specific aims were to quantify (1) amount of activity, (2) extent of seasonal and circadian variation in activity rate, and (3) ef- fect of conventional farmwork and light hours on activity rate. In addition, comparisons be- tween sexes were made. Material and methods Subjects and general managements Experiments were carried out at the Fur Farm- ing Research Station, Kannus, western Finland (63.54° N, 23.54°E), from January to Decem- ber 1993. Outdoor on-farm conditions are shown in Figure 1. Subjects were originally 9 adult male and female blue foxes born May 1992,randomly selected from the research farm breeding group which was comprised 60 fe- males and 20 males. However, due to distur- bances in female activity recordings caused by breeding, four additional non-mated females (born May 1992) were included from April on- wards. Breeding occurred during March and April. Nine of the total 13 females became preg- nant and, therefore, their cages were fitted with wooden whelping nestboxes (40 cm wide x 70 cm long x 40 cm high) from May to July. Males were not provided with nestboxes throughout the study. Test animals were housed singly in wire mesh cages, measuring 107 cm wide x 110 cm long x 70 cm high each. Each cage contained a wooden platform (made of 22 x 125 mm board) measuring 107 cm in length x 30 cm in width. The bottom of the platform re- sembled a V shape (type name: Wood V, cited by Korhonen et al. 1996). The distance of the platform from the cage roof was 23 cm. Plat- forms were placed in cages crosswise. Platforms were cleaned of faeces and urine weekly. All experimental animals remained in good health throughout the study period. Fresh-mixed fox feed manufactured by the local feed kitchen (Kannus Minkinrehu Ftd.) was supplied daily at 1300 from a feed machine. Feed primarily contained slaughter-house offal, fish and cereals. Fox feed allowances (range 250 to 450 g/d) were adjusted according to the season- al recommendations of the Finnish Fur Breed- ers’Association’s feeding standards (Berg 1986). Feeding was omitted on Sundays. Water was freely available from an automatic dispenser when ambient temperature was above O°C. Wa- 22 AGRICULTURAL AND FOOD SCIENCE IN FINLAND Vol. 7(1998): 21-29. ter was given once daily from the feed machine’s water tank at temperatures below O°C. Activity recordings Activity was measured using video camera equipment (CCD video camera 720. Bische ÜB- -480 time-lapse tape recorder, Koyo monitor, Bische 12-300 infrared light: 500 W). Each an- imal was recorded continuously for a single 24-h period for each month between January and December. The only exception was 9 pregnant females whose video recordings were omitted during whelping and lactation (May to July). However, four additional non-mated females were introduced into the study in April and re- cordings of these continued until December. Ac- tivity recordings were performed during the working week, from Monday to Friday. Males and females were typically placed in neighbour- ing cages. The only exception was the four ad- ditional females which were kept in adjacent cages. Due to only one video camera being avail- able in the present study, it was possible to record two cages during the same day. Thus, 12 work- ing days were needed to record all experimental animals for one 24-h measurement. Video tapes were analyzed by means of a continuous recording method (Martin and Bate- son 1986) using a video tape recorder (JVC vid- eo casette recorder HR-DS6OE) and a TV moni- tor (Philips model). One crucial problem in the analyses was to determine when an active bout started and ended. Mainly this problem resulted from occasional bouts (<1 min) of standing or sitting behaviour between actual activity epi- sodes. Therefore, activity in this study was de- termined to cover all activities, excluding rest- ful lying, i.e. lying awake (1-10 min) or sleep- ing (>lO min): (a) curled on belly/side, with snout stuck in tail, (b) flat on side, legs more or less stretched out, (c) flat on belly, head and front legs stretched along the floor (Kronholm 1994, Korhonen and Niemelä 1996). Initial examina- tion of the tapes revealed that the total activity consisted of two main activity patterns: (1) ac- tivity on the cage floor, and (2) jumping onto and off of the platform. Both patterns were ini- tially analyzed separately. Since the amount of jumping activity proved to be very slight (from 1 min to 29 min/24 h; mean=lo min/24 h, medi- an=9 min/24 h), it was finally summed with cage floor activity for statistical analysis. Consequent- ly, the term ‘daily active time’ includes both cage floor and platform activity. Fig. I. Mean temperature and day length at the experimental farm. 23 AGRICULTURAL AND FOOD SCIENCE IN FINLAND Korhonen, H. & Niemelä, P. Activity rates offarm blue foxes Statistical methods As a result of performing repeated monthly measurements for individual foxes, statistical analysis was conducted using a mixed-model approach. A detailed description of statistical methods used is provided by Korhonen et al. (1995,1996). Briefly, data obtained from video recordings was analysed using the following model: Y =li + S +P. + SP. + e...ijk 1 j k jk ijk where: Y, jk=activity of fox i of sex j during month k p=constant S =effect of sex i P =effect of monthk SP of sex and monthJk eyk =residual, assumed to be independent and multivariate normal with the means 0 and arbi- trary covariance matrices £- min/24 h, females mean 246 ± 63 min/24 h; median 255 min/24 h). A tendency for increased activity at the onset of the breeding season (March) was found, particularly in males. Worktime activity The duration of worktime activity in minutes, as well as its proportion of 24 h, varied (PcO.Ol) year-round (Fig. 2). In summer, the proportion of activity during worktime decreased, while the proportion of activity occuring outside worktime increased. During winter the situation was re- versed. In this case, active time was concentrat- ed around working hours. This phenomenon was more pronounced in females (Fig. 2). The pro- portion of active time during working hours was highest in October both in females (76% of total activity rate, or 229 ±76 min/24 h) and males (73.6% total activity rate, or 240 ± 72 min/24 h). Results Seasonal changes in activity Whole-year activity rate of males and females averaged 394 ±ll6 min/24 h (mean ± SD) (me- dian 393 min/24 h) and 349 ±lll min/24 h (me- dian 329 min/24 h), respectively. Monthly ac- tivity rates are presented in Figure 2. Statisti- cally significant seasonal variation (PcO.OOl) was found in the amount of activity. Mean and medianrates of monthly activities were typical- ly close, indicating a normal distribution ofdata. Differences in seasonal activity rates between sexes were generally slight, however, some dif- ferences were found. Peak activity of females was in May (mean 539 ± 157 min/24 h; median 564 min/24 h) and that of males in June (mean 471 ± 128 min/24 h; median 469 min/24 h). Thereafter, a distinct decrease in activity rate was observed. Lowest values were found in Septem- ber (males mean 290±6l min/24 h; median 281 Circadian activity The present foxes displayed a clear circadian activity rhythm (Fig. 3). During each month, the highest activity typically occurred after the start of farm work. An intermediate phase of activity often occurred in the evening. In December, the activity was distinctly concentrated between sun- rise and sunset in both sexes. A clear resting phase occurred in the early hours during Decem- ber and September. In June, animals were active throughout the 24-h period, but during that time the dark period was also very short. During the breeding season in March, activity was widely distributed over the whole 24-h period. This pat- tern was more pronounced in males. Discussion Nocturnal animals often have two activity peaks which occur in the evening and early morning 24 AGRICULTURAL AND FOOD SCIENCE IN FINLAND Vol. 7(1998): 21-29. (Aschoff 1962). Wild red foxes have been con- sidered to be mainly nocturnal since over 50% of their activity appears to occur between 1700 and 0900 (Abies 1969). Wild arctic foxes have been documented to have either clear (Eberhard! et al. 1982, 1983) or weak nocturnal patterns of activity (Frafjord 1992a). Nocturnal patterns in nature are adaptations to prey availability and predator avoidance. However, learned nocturnal patterns may be partly sustained when wild fox- es are taken into captivity (Tembrock 1958, Österholm 1966). In contrast to wild foxes, farm- born blue and silver foxes seem to have activity patterns that are more concentrated on daytime hours (Kaleta and Brzozowski 1985, Korhonen 1988, Korhonen and Alasuutari 1994, Mononen et al. 1996. Rekilä et ai. 1996). The present re- sults also showed that activity of farmed blue foxes occurred mainly during light hours. In summer, when there was light almost through- out the 24 h, foxes were also more active day around than during winter. In winter, light hours as well as activity were concentrated on work- ing times. Thus, it seems that the duration of light significantly affects the activity of farm blue foxes. Actually the same occurs in the wild, but the situation is reversed with wild foxes being most active outside light hours. The explanation Fig. 2. Seasonal changes in total and worktime activity rates (mean ± SD). Worktime was between 0800 and 1600, 25 AGRICULTURAL AND FOOD SCIENCE IN FINLAND AGRICULTURAL AND FOOD SCIENCE IN FINLAND 26 Fig. 3. Examples of circadian rhythm of activity in males and females during four different months. Sunrise and sunset are marked with arrows. Broken lines are female activity curves. Korhonen, H. & Niemelä, P. Activity rates offarm blue foxes VW. 7(1998): 21-29. to this difference between farm and wild condi- tions is due to farmed foxes not having enemies which need to be avoided. While food is also offered to them during daytime, there is no rea- son why they should be very active in the dark. In the study ofTembrock (1958), captive arc- tic foxes were most active during the breeding season in March, but shortly before whelping they became rather inactive. Thereafter, they became active again but after mid-June their lo- comotorive activity decreased. The next activity peak was observed in autumn. Österholm (1966) presented rather similar results for captive red foxes. The results of the present study are in good agreement with these studies, confirming the conclusion that activity rates of captive foxes vary according to season. In the wild, activity rates of arctic foxes also show seasonal varia- tions. Activity is highest in the summer and ear- ly autumn (Frafjord 1992a, b). This is obviously due to two reasons: (1) wild foxes must be very active in order to gain enough food and subcuta- neous fat reserves for winter, and (2) dispersion of litters occurs in late summer or early autumn, which leads to animals migrating to new living and foraging areas (Eberhard! and Hanson 1978, Eberhardt et al. 1983). In contrast, on farms, feed is provided by farmers and therefore, foxes do not need to move in search of food. Nor is dis- persion possible from cages. In late July, how- ever, farm foxes are typically weaned from their mothers and put into their own cages. Despite these differences, a tendency for increased ac- tivity in farm foxes during late autumn was also found in the present study. The explanation for this phenomenon is unclear. However, farmers normally limit food availability at this time to avoid excessive obesity. This was also the case in the present study. Foxes are therefore slightly hungry and tend to be restless. In the wild, arctic fox movements have been classified into four categories; (1) local move- ments, (2) general daily travels ofindividualfox- es, (3) sporadic movements and (4) seasonal movements and migration (Chesemore 1975). For technical reasons, systematic information on arctic fox activity in nature is often based on the first category, and even then this information is typically limited to the denning season. During breeding season, adults have been documented to rest most of their time, i.e. 60-90% (Frafjord 1992b) or 79-80% of the total 24 h (Garrott et al. 1984). This data shows that in nature at the time when energy demand of a litter is at its high- est, arctic foxes may be inactive for longer peri- ods than their captive counterparts. General observations from the wildobtained from several studies indicate that male arctic foxes tend to roam more than females, particu- larly during the winter period (Pulliainen 1965, Vibe 1967, Bannikov 1969). Also the results from group-housed blue foxes housed in semi- natural enclosures (Korhonen and Alasuutari 1994), and those from singly-caged blue foxes (Korhonen and Niemelä 1995), showed that males were more active than females in March. Parallel evidence also emerged from the present results with the difference in activity rates for males being highest in March and December. The tendency for higher winteractivity in wild males is associated with the need to seek for breeding partners and new living territories. Although fox- es often are considered rather solitary, they may also live in groups. Groups are typically com- prised of several breeding and non-breeding fe- males with a lesser number ofmales (Hersteins- son and Macdonald 1982,Eberhardt et al. 1982). Social tension with increased agressive interac- tions is pronounced, particularly in males prior to and during the breeding season (Korhonen and Alasuutari 1994, 1995). Thus, pressure for dis- persal and roaming would be higher in males than females. The fact that winteractivity of fox- es on farms resembled that of wild foxes can be explained by the presence of social and sexual pressure on farms also. Although breeding males are kept singly in their cages, it has been found that a kind of social hierarchy also exists on farms (Korhonen and Niemelä 1993). Scent odours and vocal communication are the means by which farm foxes communicate social and sexual state. A crucial problem when comparing activities of farm foxes to their wildrelatives is that activ- 27 AGRICULTURAL AND FOOD SCIENCE IN FINLAND Korhonen, H. & Niemelä, P. Activity rates offarm blue foxes ity results gained from wild animals often con- centrates on total active time,which does not dis- criminate behaviours such as standing, sitting, eating, self-grooming, defecation, and occasional short rest periods. Therefore, activity rates re- ported in wild animals can easily exceed those of farm animals. Another problem is that data from wild animals is not necessarily expressed as activity per 24 h. Urquhart (1973) and Eber- hard! and Hanson (1978), for instance, reported the activity ofarctic foxes as 27 km and 24 km/d, respectively. It is difficult to assertain from these figures the time taken to travel these dis- tances. However, more comparable data is also available. In Svalbard, Frafjord (1992a) recorded that wild artic foxes were active for about 34% of the day (490 min/24 h) and captive ones for about 25.3% (364 min/24 h). In seminatural en- closures, mean activity of arctic blue foxes was 29.2%, i.e. 421 min/24 h (Korhonen et al. 1997). Activity of blue foxes in conventional farm cag- es was previously reported to vary from 127 min/ 24 h (Korhonen 1988) to 311 min/24 h (Korho- nen and Niemelä 1995). However, when stand- ing was also included, the activity in the study of Korhonen (1988), for instance, rose to 231 min/24 h. In the present study, the yearly mean activity was higher (372 min/24 h) than that in previous farm cage studies. The differences be- tween results ofvarious studies can be explained by differences between farms, individuals and/ or recording methodology. Acknowledgements. Thanks are due to Mr. Pekka Toikkanen, Mr. Aimo Joki-Huuki and Mr. Terho Lindqvist for general care of experimental animals. Further thanks to Mr. Pekka Eskeli and Mr. Jaakko Huuki for skillful assistance during video recording. Mrs. Sanna Moisio is warmly acknowl- edged for dilligent work in analysing the video tapes, and Mr. Pekka Siirilä for computer assistance. References Abies, E.D. 1969. Activity studies of red foxes in south- ern Wisconsin. Journal of Wildlife Management 33: 145-153. Aschoff, L. 1962. Spontane Lokomotorische Aktivität. Handbuch fur Zoologie8: 1-74. Bannikov, A.G. 1969, Arctic fox in the U.S.S.R.: biologi- cal premises of productivity. In: Fuller, W.A. & Kevan, P.G. (eds.). Productivity and conservation in north- ern circumpolar lands. International Union for Con- servation of Nature and Natural Resources. New Series Publication 16: 121-130. Bakken, M., Braastad, 8.0., Harri, M., Jeppesen, L.L. & Pedersen, V. 1994. Production conditions, behaviour and welfare of farm foxes. Scientifur 18: 233-248. Berg, H. 1986, Rehutietoutta Turkiseläinkasvattajille. Turkiseiäintutkimuksia 23. Suomen Turkiseläinten Kasvattajain Liitto ry. Vaasa. Painopintaky. 99 p. Braastad, 8.0. 1992. Progress in the ethology of foxes and mink. Norwegian Journal of Agricultural Sci- ences (Supplement) 9: 487-504. Chesemore, D.L. 1975. Ecology of the arctic fox (Atopex lagopus) in North America - a review. In: Fox, M.W. & Krieger, R.E. (eds.). The wild canids, their system- atics, behaviour, ecology and evolution. Pubi. Co, Malabar, Florida. Eberhardt, L.E., Garrott, R.A. & Hanson, W.C. 1983. Win- ter movements of arctic foxes, Atopex lagopus, in a petroleum area. Canadian Field-Naturalist 97: 66- 70. - & Hanson, W.C. 1978. Long-distance movements of arctic foxes tagged in Northern Alaska. Canadian Field-Naturalist 92: 386-389. -, Hanson, W.C., Bengtson, J.L., Garrott, R.R. & Han- son, E.C. 1982. Arctic fox home range characteris- tics in an oil-development area. Journal of Wildlife Management 46: 183-190, Frafjord, K. 1992a. Behavioural ecology and behaviour- al energetics in the Arctic fox, Atopex lagopus. Ph.D. Thesis, University of Bergen, Norway. -1992b. Denning behaviour and activity of arctic fox Atopex lagopus pups: implications of food availabili- ty. Polar Biology\2: 707-712. Garrott, R.A., Eberhardt, L.E. & Hanson, W.C. 1984. Arctic fox denning behaviour in northern Alaska. Canadian Journal ofZoology 62: 1636-1640. Harri, M., Ahola, L., Kasanen, S., Mononen, J. & Rekilå, T. 1995. Key features of housing design in farm fox- es. Resultater av senaste års nordisk pälsdjursforsk- ning. NJF-seminarium, 4-6 October 1995, Goethen- bourg, Sweden. 13 p. Hersteinsson, P. & MacDonald, D. 1982. Some compar- isons between red and arctic foxes, Vulpes vulpes and Atopex lagopus, as revealed by radio tracking. Symposium ofZoology SocietyLondon 49: 259-289. 28 AGRICULTURAL AND FOOD SCIENCE IN FINLAND Jeppesen, L.L. 1996. Progress in the ethology of fur an- imals. Animal Production Review, Applied Science Reports 27; 9-11. Kaleta, T. & Brzozowski, M. 1985. The activity of farm silver fox ( Vulpes vulpes) in summer. Scientifur 9: 179-180. Korhonen, H. 1988. Seasonal changes in activity and behavioural patterns of farm-raised foxes (Alopex lagopus). Scientifur 12: 21-26. - & Alasuutari, S. 1994. Social relationships and re- productive performance in group-living arctic blue fox- es. Agricultural Science in Finland 3: 49-58. - & Alasuutari, S. 1995. Dominance relations in cap- tive groups of adult and juvenile arctic blue foxes (Alopex lagopus). Polar Biology 15: 353-358. -, Alasuutari, S., Mäkinen, A. & Niemelä, P. 1997. In- ter- and intraspecific competition between the fox species Alopex lagopus and Vulpes vulpes: an eval- uation trial under penned conditions. Polar Biology 17; 330-336. - , Ketoja, E. & Niemelä, P. 1995. Comparison of day- time use between platform types, materials, ceilings and experiences in juvenile blue foxes (Alopex lago- pus). Applied AnimalBehaviour Science 45:125-138. - & Niemelä, P. 1993. Social rank and reproductive per- formance in farmed blue foxes. Scientifur 17: 1 SI- -185. - & Niemelä, P. 1995. Comparison of production re- sults between blue foxes housed with and without platforms. Agricultural Science in Finland4: 351-361. - & Niemelä, P. 1996. Seasonal changes in platform use by adult farmbred silver foxes (Vulpes vulpes). Agricultural and Food Science in Finland 5: 3-15. - , Niemelä, P. & Tuuri, H. 1996. Seasonal changes in platform use by farmed blue foxes {Alopex lagopus). Applied Animal Behaviour Science 48: 99-114. Kronholm, A. 1994. Sexual differences Inparental invest- ment and behaviour during weaning in arctic foxes, Alopex lagopus, in a semi-natural environment. Sveriges Lantbruksuniversitet, Veterinärmedicinska fakulteten. Specialarbete 20. Skara, 1994. 35 p. Martin, P. & Bateson, P. 1986. Measuring Behaviour: An Introductory Guide. Cambridge University Press, London, UK. 200 p. Mononen, J., Harri, M. & Rekilä, T. 1996. Comparison of preferences of farmed silver and blue foxes for cages with and without a nest box. Acta Agriculturae Scan- dinavia 46: 117-124. Österholm, H. 1966. Kaukoaistien merkitys ketun ravin- nonetsinnässä. Suomen Riista 18: 50-65. Pulliainen, E. 1965, On the distribution and migrations of the arctic fox (Alopex lagopus L.) in Finland. Aquilo Serie Zoology 2: 25-40. Rekilä, T, Mononen, J. & Harri, M. 1996. Effect of in- side-cage and outside-cage environment on behav- iour test performance of blue foxes (Alopex lagopus). Acta Agriculturae Scandinavia 46: 247- 252. Tembrock, G. 1958. ZurAktivitätsperiodikbei Vulpes und Alopex. Zoologische Jahrbuch, Abteil Allgemeine Zoologische Physiologie 68: 297-324. Urquhart, D.R. 1973. Oil exploration and Banks Island wildlife: a guide for the preservation of Caribou, Muskox, and Arctic foxpopulations on Banks Island. N.W.T. Game Management Division Report, Govern- ment of the Northwest Territories. 105 p. Vibe, C. 1967. Arctic animals in relation to climatic fluc- tuations. Meddelser om Grönland 170: 1-227. SELOSTUS Tarhattujen sinikettujen vuodenaikainen ja vuorokautinen aktiivisuus Hannu Korhonen ja Paavo Niemelä Maatalouden tutkimuskeskus Tässä työssä tutkittiin tarhattujen sinikettujen (9 uros- ta, 13 naarasta) vuodenaikaista ja vuorokautista ak- tiivisuutta. Kettujen käyttäytymistä videokuvattiin 24 tunnin jakso kerran kuukaudessa vuoden ympäri. Urosten keskimääräinen aktiivisuus oli hieman kor- keampi (394 ±ll6 min/vrk) kuin naaraiden (349 ± 111 min/vrk). Molempien sukupuolien aktiivisuus vaihteli vuodenajoittain. Naaraat olivat kaikkein ak- tiivisimpia toukokuussa (539 ± 157 min/vrk), kun taas urosten aktiivisuushuippu sattui kesäkuulle (471 + 128 min/vrk). Pienimmät aktiivisuusarvot mitattiin syyskuussa. Talvella kettujen aktiivisuus keskittyi pääosin työaikaan (klo 8-16). Kesällä työajan ulko- puolinen aktiivisuus lisääntyi selvästi. Tulosten pe- rusteella valon määrän lisääntyminen kesällä lisää aktiivisuutta. Talvella valoisaa on lähinnä työaikana, mikä selittää sen, että tarhakettujen aktiivisuus ajoit- tuu tällöin työaikaan. 29 Vol. 7(1998): 21-29. AGRICULTURAL AND FOOD SCIENCE IN FINLAND