ࡱ;   !"#$%Root Entry FsCompObjbWordDocumentf?ObjectPoolktskts 4@   FMicrosoft Word 6.0 Document MSWordDocWord.Document.6;  Oh+'0$ H l   D hD:\WINWORD\TEMPLATE\NORMAL.DOT Djuro HuberIvica PosavecIvica Posavec@AXaܥe- e2f?/:p:pp:p:p:p:p::::::: ;:>?;;;;;;;;y<{<{<{<<=|>>T-?9>p:;;;;;>;p:p:;;;;;;p:;p:;y<:,:Jp:p:p:p:;y<;e;21 August 1996 Djuro Huber Biology Department Veterinary Faculty Heinzelova 55 10000 Zagreb Republic of Croatia Phone: 385-1- 2390-141 Fax: 385-1- 214-697 RH: Bear traffic kills in Croatia. Huber et al. Traffic kills of brown bears in Gorski kotar, Croatia DJURO HUBER, Biology Department, Veterinary Faculty, Heinzelova 55, 10000 Zagreb, Republic of Croatia, e-mail: huber@mavef.vef.hr JOSIP KUSAK, Biology Department, Veterinary Faculty, Heinzelova 55, 10000 Zagreb, Republic of Croatia, e-mail: kusak@mavef.vef.hr ALOJZIJE FRKOVI], Croatian Forests, Delnice Forestry Office, Supilova 32, 51300 Delnice, Croatia Abstract: At least 73 European brown bears (Ursus arctos) have been killed by vehicles in the forest region (1500 km2) of Gorski kotar, Croatia, from 1963 to 1994. Fifty-one (70%) were killed by trains along the Zagreb - Rijeka railway and 22 (30%) were killed by motor vehicles along roadways in Gorski kotar. Several parameters were measured at known collision sites (N = 46) and at an appropriate number of random sites (N = 61) along roads and railroads. Slope angle and length, as well as longitudinal and perpendicular visibility at accident and random sites, were not significantly different. We concluded that microsite topography had little or no influence on the occurrence of bear traffic accidents. Instead, food sources related to human activities (such as garbage along roads) may have served as local attractants to bears and were found near at least 15 (33%) accident sites, but at only 5 (8%) of the random sites (P < 0.01). We found that 3 main corridors for bear movements were cut by traffic lines. Provisional mitigation measures were proposed to reduce conflict between bears and traffic, and an artificial tunnel or green bridge (100.5-m long) was added to a new highway project. Int. Conf. Bear Res. and Manage. 10:000-000 Key words: Croatia, European brown bear, mortality, traffic kills, Ursus arctos ____________________________________________________ Brown bear (Ursus arctos) population in Gorski kotar, Croatia, have grown substantially from its 1946 low to a density of approximately 1 bear/10 km2 by the early 1980s (Frkovic et al. 1987) and seems to be stable since. Loss of habitat and direct human-caused mortality may cause the population decline in the future. The more humans influence bear range, the more bear deaths occur from human factors such as shooting, den disturbance and abandonment of cubs, nuisance bear control, and traffic. Roads and railroads can lead to habitat fragmentation and deaths due to collisions with motorized vehicles. Bears need large ranges because of their feeding regime, reproductive behavior and denning requirements (Huber and Roth 1993). Bears opportunistic food-finding behavior may attract them to discharged human foods, carrion, or preferred vegetation frequently located along travel routes. Ueckermann (1964) published data on traffic kills of 11 mammalian species in Germany. Traffic induced bear mortality have been documented in Europe (Frkovic et al. 1987 in Croatia, Kaczensky et al. 1996 in Slovenia) but no analyses of such incidents have been published. Wooding and Brady (1987) and Warburton et al. (1993) reported on American black bears (U. americanus) killed on roads in Florida and North Carolina (both USA). Traffic kills of European brown bears in Croatia comprised 11% of total mortality from 1946 to 1985 when 31 (of 281) were killed by traffic in 40 years or 0.78 bears per year (Frkovic et al. 1987). In recent years (1986 ( 95) traffic induced mortality rose to 19% of total mortality when 42 (of 217) were killed by traffic or 4.2 bears per year. This alarming data prompted us to study traffic accidents involving bears. We wanted to determine why some sites had more bear-vehicle accidents than others, and to propose mitigation measures if feasible. Our hypothesis was that the higher local bear mortality was related to: (1) low visibility associated with vegetation density, slope, and curves on travel routes; (2) interruption of bear travel corridors; (3) various food sources attracting bears to travel routes. We thank to the Croatian Ministry of Science and the International Association for Bear Research and Management for financial support. D. Novosel, T. Gomer~i} and G. Gu`vica assisted in the field work. Special thanks to the associate editor and reviewers for improving our manuscript. STUDY AREA The Gorski kotar region (1,500 km2) comprises the western edge of occupied bear range in Croatia (Fig. 1). The region is mountainous, with elevations ranging from 0 to 1,500 m. Forest covers about 70% of the area, and the main road and railroad from the Croatian capitol Zagreb to the Adriatic Sea coast run through the middle of the Gorski kotar area. From 6,600 to 13,100 vehicles/day use this road. Construction of a new highway connecting Zagreb to the Adriatic Sea is under way presently. METHODS Records of traffic-killed bears have been kept by the third author since 1963. The records included the exact site and date of collision, sex and age of the bear, and the type of vehicle involved in each collision. Bears were classified as subadults ((3 years) and adults (>4 years old) by size and appearance, but since 1981 have also been aged by counting the cementum layers on the first premolar tooth root (Stonenberg and Jonkel 1966). At each known collision site (N = 46) and at 61 random sites along roads and railroads we measured several parameters: longitudinal and perpendicular visibility, slope angle and length, distance to the nearest house, and the time of audial detectability of trains before reaching the measured site. Recent collision sites were visited within a few days of the accident and the older ones in the same season in which the accident happened years(s) before. Random points were selected at each full kilometer of road and railroad in the bear range. If a known collision site appeared to be between 2 random points the closer one was jumped over to the next full kilometer. Longitudinal visibility was determined by curves in the roads and railroads, and perpendicular visibility by vegetation cover and topography. The distance at which >90% of the standing assistant(s body was invisible we considered the limit of visibility. The length of a slope was measured from our site to the first ridge or valley bottom. Local attractants for bears were defined as (1) any food source related to human activities and included garbage along roads and grain spills from trains, and (2) presence of fruit-bearing vegetation along the road or railroad right-of-way. Chi square ((2) tests were used to compare the differences between habitat variables at bear kill and random sites. Alpha levels were 0.05. RESULTS At least 73 bears have been killed by traffic in Gorski kotar, Croatia from 1963 to 1994 (Fig. 2). Fifty-one (70%) were killed along the Zagreb - Rijeka railroad, and 22 (30%) were killed on roads in Gorski kotar (Fig. 3). Of all bears killed, 26 (36%) were male, 33 (45%) were female and 14 (19%) were of unknown sex. Forty-six (63%) bears were subadults ((3 years), 17 (23%) were adults (>4 years), and 10 (14%) were of unknown age. Collisions with bears occurred in all months of the year (Fig. 4). In six cases, >1 bear died in an incident: 3 cases involved mother and cub(s) and 3 cases involved 2 cubs each. All multiple deaths of bears were train-related accidents. On 2 occasions, bears were known to have survived automobile collision and escaped from the site. Means of longitudinal and perpendicular visibility between accident and random sites were not significantly different. The slope at the accident sites was not significantly steeper than at randomly selected sites (36( vs. 33(, respectively). Mean lengths of the slope at accident and random sites were both 51 m. On average trains at accident sites were heard 4 seconds later (shorter) than the trains at random sites (31 vs. 35 seconds, respectively) but this difference was not significant. Food availability was determined to attract bears to travel ways in at least 15 (33%) of the accident sites compared to only 5 (8%) of the random sites (P<0.01, (2 = 8.74). Furthermore, fresh bear sign (unrelated to the accident) was found at 4 accident sites, whereas none was found at the random sites. Bear-vehicle collisions occurred most frequently at 6 sections of roads and railroads (Fig. 5). These sections were: (1) Railroad Gomirje-Vrbovsko (9 bear collisions), (2) Railroad Vrbovsko-Moravice (7 collisions), (3) area from Delnice to Dedin (6 collisions on road, 1 railroad), (4) area of Lokve (road, 2; railroad, 4), (5) Railroad Li~-Drivenik (5 collisions), and (6) Kvarner area (road, 4; railroad, 7). DISCUSSION We concluded that microsite topography had little or no influence on bear traffic accidents. Although not significant, the slight tendency for accidents to occur at steeper and more forested places reflects areas less suitable for human settlements and therefore more likely to be used as bear travel corridors. Sites of frequent accidents indicated existence of 3 bear movement corridors that have been cut by human traffic ways (Fig 5). Provisional mitigation measures were already proposed to reduce the conflict of bears and traffic on roads and railroads. For a highway currently under construction through bear habitat in Gorski kotar, we proposed at least 6 tunnels and/or viaducts in addition to those planned due to topographic reasons. So far, 1 artificial tunnel or "green bridge" (100.5 m long) was incorporated into the highway project. A number of railroad tunnels should be constructed at critical points. Bears feed on variety of food items (Cicnjak et al. 1987) and are attracted to any abundant and/or renewable food source. Because a large proportion of the accidents could be related to food attractants, we recommend removing all human created bear food sources from along travel ways. LITERATURE CITED Cicnjak, L., D. Huber, H.U. Roth, R.L. Ruff, and Z. Vinovrski. 1987. Food habits of brown bears in Plitvice Lakes National Park, Yugoslavia. Int. Conf. Bear Res. and Manage. 7:221(226. Frkovic, A., R.L. Ruff, L. Cicnjak, and D. Huber. 1987. Brown bear mortality in Gorski kotar, Yugoslavia. Int. Conf. Bear Res. and Manage. 7:87(92. Huber, D., H. U. Roth. 1993. Movements of European brown bears in Croatia. Acta Theriologica. 38:151(159. Kaczensky, P., F. Knauer, T. Huber, M. Jonosovic, and M. Adamic. 1996. The Ljubljana - Postojna highway ( a deadly barrier for brown bears in Slovenia? J. Wildl. Research. 1(4):000-000 (in print). Stonenberg, R. P., and C. J. Jonkel. 1966. Age determination of black bears by cementum layers. J. Wildl. Manage. 30:411-414. Ueckermann, V.E. 1964. Erhebung ber die Wildverluste durch den Strassenverkehr und die Verkehrsunfalle durch Wild. Zeitschrift fr Jagdwissenschaft. 10:142(168. (In German with English summary.) Warburton, G.S., R.C. Maddrey, and D.W. Rowe. 1993. Characteristics of black bear mortality on the coastal plain of North Carolina. Proc. Annu. Conf. Southeast Assoc. Fish and Wildl. Agencies. 47:276(286. Wooding, J.B. and J.R. Brady. 1987. Black bear roadkills in Florida. Proc. Annu. Conf. Southeast Assoc. Fish and Wildl. Agencies. 41:438(442. FIGURE CAPTIONS Fig. 1. Location of Croatia in Europe and the Gorski kotar study area in Croatia. Fig. 2. Five-year averages of traffic-caused brown bear mortality in Gorski kotar, Croatia, from 1963 to 1995. Fig. 3. Sex distribution of brown bears killed on railroad tracks and roads in Gorski kotar, Croatia. Fig. 4. Cumulative number of brown bears killed by traffic by month in Gorski kotar, Croatia, from 1963 to 1995. Fig. 5. Main brown bear traffic accident points in Gorski kotar, Croatia: (1) Railroad Gomirje-Vrbovsko, (2) Railroad Vrbovsko-Moravice, (3) area from Delnice to Dedin, (4) area of Lokve, (5) Railroad Li~-Drivenik, and (6) Kvarner area (road, 4; railroad, 7). 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