　ISHIDA, Ken. 2001. Black bear population at the moutainous road construction area in Chichibu, central Japan. Bull. Tokyo. Univ. For. 105: 91-100.

Black Bear Population at the mountain road construction area in Chichibu, Central Japan
Ken ISHIDA^{1, 2}
¹, University Forest in Chichibu, University of Tokyo, Chichibu, Saitama 368-0032;
², Present Address, Laboratory of Forest Ecosystem Sciences, School of Agricultural and Life Sciences, the University of Tokyo, Tokyo 113-8657

Introduction
A part of the national road route 140 was constructed at Chichibu, Saitama, central Japan in 1980s and 1990s. It goes through a steep mountainous area covered with well-reserved natural temperate forest of University Forest in Chichibu, the University of Tokyo (Ishida et al. 1991 , Ishida et al. 1994, UFUT 1998). The high biodiversity in this area, the impact of the road construction and traffic on the forest ecosystem, and animal populations has been interested in.
The university forests of the University of Tokyo has been trusted and funded the nature survey at the University Forest in Chichibu, around the national road, in 1986 - 1997 by Ministry of Construction and later by Saitama Prefecture. The author conducted an ecological survey as a part of this research project in ten years of 1990 - 1999. The intimate objective of the survey is to estimate the habitat fragmentation of large mammal populations around the road (Ishida et al. 1991), gaining the actual data of the black bear population in this area (Ishida et al. 1994).
The Black Bear (Ursus thibetanus japonicus) is one of the largest and common mammals in the broad-leaf deciduous forest in central to northern Honshu Island, Japan, though the small populations are extinct or threatened in western Japan (Hazumi 1996, Ishida 1995). The species is sometimes thought to be a symbol of forest biodiversity.
The Black Bear is a "phytophagous carnivore" adapted to the seasonally and unpredictably changing resources, and its breeding is supposed to be strongly dependent to the masting of mainly to beech family trees in this area (Ishida 1995). The mortality of adult bears is supposed to be an important factor to escape population extinction (Miura & Horino 1999). Each individual of an animal not always behaves for the fittest for the population survival or reproduction, and population fragmentation can have a significant affect on the population (Matsuda & Abrams 1994, Ishida 1995). The road has two short and one six-kilometer long tunnels in this area, and they are expected to function as a kind of corridor for the bear. To learn about these, we need to estimate their density, home ranges, and dendrological parameters.
In the main habitat of natural broad-leaf deciduous forests with nut and acorn trees such as Fagus crenata, F. japonica, Quercus crispula and Q. serrata, the field marks of the black bear, such as fecal drops, claw marks on the trunks and feeding platform in the crowns, are indicators of their habitation. However direct observation of the bear in nature is almost impossible, as they escape human being in the natural forest and walk quietly with soft palms. So capturing bears is one of the effective survey measurements to detect their population and ecology. We gained some results of their density and home ranges, capturing bears and marking them with year tags, microtips and transmitters, in this study.

Study area
Study area is in the west part of Ohtaki-village, westernmost Saitama, called Oku-Chichibu, central Japan. It is near the border to neighboring four prefectures, Tokyo, Yamanashi, Nagano and Gumma (Fig. 1, Fig. 4). There are two larger valleys in the main research area, Takikawa and Irikawa Valleys. The National Road route 140 has constructed on the northern slope of the Takikawa valley and there is a small and short mountain road of the University Forest in Irikawa Valley. The Paleozoic and Mesozoic bedrock is hard and has been scraped away by erosions over a hundred millions of years. So the slope is steep especially close to the main valleys of Takikawa and Irikawa, and at the entrance of their branch valleys (Ishida et al. 1993).
An amount of primitive and secondary broad-leaf natural forest is left around there. The elevation of the study area is from about 600m to 2,000m. Black bears mostly stay in a cool temperate deciduous forest and mixed forest up to about 1,500m.

About 160 species of trees are recorded in the University Forest in Chichibu, the University of Tokyo, and the vegetation diversity is high according to large elevation range and complex terrain with rich rain fall (UF in Chichibu 2000).
The dominant species are beech (Fagus crenata) and japanese beech (F. japonica) on the slopes, hemlock (Tsuga sieboldii) and fir (Abies firma) on the ridges, and senwood (Fraxinus spaethiana) in the valley of the slopes with much rock. Most of the area is covered second growth deciduous forest of oaks (mainly Quercus crispula), beech, japanese beech, chestnut (Castanea crenata), maples (Acer spp.), cherry trees (Purnus spp.) and mix of other species. The proportions of species are varied at place to place. There are vines of wild grape (Ampelopsis brevipedunculata) and arguta (Actinidia arguta), bushes of rasberries (Rubus spp.) and so on, preferred by bears. Nuts and acorns of beeches, oaks and chestnut trees are important food for the bear (Hashimoto 1995). Nuts and acorns are characteristic for their large and irregular annual fluctuation of crops or masting (Kelly 1994, Miguchi 1996). In this area, however, the main four species' (F. crenata, F. japonica, Q. crispula and C. crenata) masting are not always synchronized, and the food condition for bears in autumn appeared less fluctuated than those of the other area in Honshu Island.

Method
We set 15 bear traps at 13 sites in our university forest (Fig. 2, Table 1). Traps are made of two or three oil barrels attached each other and a beehive was set inside as the bait in its end to make the bear pull the trigger line connecting to the front door (Ishida et al. in preparation-b). Seven traps at seven sites were set at Takikawa Valley around the National Road, and the others at northern next Irikawa Valley. With this trap allocation we compared the two areas. We tried to capture the bear through mid April to mid December in 1990 to 1992, or mainly during July, August and earlier September, from 1993 to 1999. As almost all bears were caught during the summer in the previous years, the trapping period was shortened to those seasons in the latter seven years.
All of the trapped bears were tagged on the ear and those were attached with a micro tip since 1995. We also attached collar mounted radio transmitters (ATS and Teronics corporation, USA) on larger individuals.
We located the bears with a radio transmitter roughly referring the direction and strength of the wave, presence or absence of ridges as barriers or reflectors of the radio wave, with Yagi and/or rod-anntenas, and decide the site into a small valley or ridge, then around a circle of a hundred meters in diameter. The home ranges are fixed with the outline of all location points or circles.

Results
Capture of Bears
22 females and 36 males were caught by 136 times, during the study period of nine seasons. We caught no bear in 1990. The individual number was three in 1991, nine in 1998 and five in 1999. It was Five to seven females and six to ten males by 18 to 24 times, each year, in 1992 to 1998. Recaptured bears are caught all the year and area after 1993 (Table 2), and this result reflects capturing effect on the results is minimum.
The number of males was larger than females (Table 3). The difference between the sexes in captured number was mainly was caused by the immature bear numbers, such as five females (<30 kg) and 16 males (<40 kg) in total. The sex ratio of trapped adult bears is almost equal every year except at Takikawa area in 1993 when no male was caught (Table 3). This result suggests the density of the male is as same as that of the female.
The numbers of bears captured at Takikawa and Irikawa areas were not significantly different in each sex or year, except for no males in 1993 in Irikawa area. The female number captured at Irikawa area was smaller than male in 1995. It seemed partly caused of two small juvenile males, captured repeatedly in nine times and the decreased trap availability for this area in this year.

Home rages and density
We attached 34 transmitters on 23 individuals. Their movement of 16 individuals was traced continuously. Two reports of detection by hunting from remote areas were gained in 1995 and 2000 for males.
The outlines of the home ranges of six, eight and seven female bears in 1994, 1995 and 1996 are shown respectively in figures 3-1 to 3-3. All of these female ranges are overlapped or touched each other. So it is supposed that all the breeding female bears were monitored with radio transmitters in these three years. Dividing the total area of these ranges by the number of them, we estimated the average density as about one bear per 7 to 8 square kilometers. The ranges are similar between the Takikawa and Irikawa areas, but the range of the female O76 close to the national road seems longer in east - west direction. The main valleys of Takikawa and Irikawa were functioned as female home range border.
The outlined home range of the male W1 was up to 60 square kilometers in 1991-1992, and 14 square kilometers in 1993. However I could hardly estimate the area for the other males or for the same male in the other years, they often crossed the main valleys and ridges of this area.
The male S26 was caught at Iriyama site (Table 1 and Fig. 1) on July 14, 1992, and recaptured at Takadaira site, about three kilometers in direct distance from the first capture on July 24. It was traced with a radio transmitter moving around Takikawa area till September 18. We learned later this bear was shot at Ichinose, Yamanashi, about nine kilometers far from Takadaira, on October 12. It was a poor crop year of all the nuts, acorns and other fruits in Oku-chichibu area, and there were many Oak trees with partly fruited acorns at Ichinose.
Another male S42 was reported to be shot at a bee raising site in Kitaaiki Village, Nagano, about 25 kilometers far from Oku-Chichibu, in August 12, 2000 (Fig. 4). The male was last captured at Wasabizawa site (Table 1 and Fig. 1) on July 19, 1997. There is a ridge of about 2000m in altitude between the capture and shot areas in both cases.
Black bears mostly inhabited broad-leaf forests. We do not have the data of the ratios of vegetation preferences, for we cannot locate their position exactly in our study area.

Discussion
The whole results of capturing bears showed there inhabits a high density population, with one breeding female per 7 to 8 square kilometer and other bears, of the Japanese Black Bear in Chichibu. This condition seemed maintained through the construction of the national road at least till now.
The lack of male capture at Takikawa (national road) area in 1993 and the recovering by immature males in the following years, suggests an indirect fragmentation effect of national road, interpreted as follows. It was a poor crop years of nuts and acorns in this area in the autumn of 1992, and the male S26 was proved to be shot by man about nine kilometers from the area. Other unmarked males can have a similar fate in this area. The adult males were remained in Irikawa area with larger sub population in better natural forest, but it might take a couple of years for adult male population recovery in Takikawa area, which is partly bordered with national road on the north. This observation indicates a part of larger scale hunting pressure can affect the local sub population structure, at least temporally. Male black bears move around in a large distance of ten, twelve or more kilometers, probably constantly, monitoring food resources and female bears.
Usually more active males are supposed to move positively in such situations and easy to be shot, and less active males with negative behavior also in mating will remain, leading further decrease of reproductive rate of the whole population. It is proved with a mathematical model simulation that such a mechanism can exist (Matsuda & Abrams 1994). Miura and Horino's result (1999) indicates hunting pressure on adults itself can be a significant factor to decrease the population size and increase the extinction rate of the black bear population.
There could not be detected any direct effect by road construction and traffics, such as declining density or activity around the road, or successive effect on the bear population structure, such as a luck of mature individuals around the road in a long time. Although the road structure on a steep slope is a strong barrier for most of the wildlife to move across and fragments their habitat (Ishida et al. 1991), the author think the two small tunnels and a six kilometer long Karisaka tunnel structure of the national road function to preserve corridors for the wildlife to across the road. Providing such a large-scale corridors is important to protect a population of large mammals.

Acknowledgment
This research was partly supported by the Nature Survey fund in the University Forest in Chichibu, by the Ministry of Construction trusted to the University Forests, the University of Tokyo.
Mr. Y. Hashimoto, UT, contributed a large part of field works. Mr. T. Hazumi, Wildlife Management Office Ltd., kindly provided a wide variety of knowledge and techniques to conduct the bear research at the start, and advised on the course of the study. Ms. K. Kishimoto and Ns. A. Yasutake, WMO, also advised on the sampling methods of captured individuals.
Mr. R. Yamanaka, T. Akaiwa of UF in Chichibu, and Mr. Y. Kamizuka of Ohtaki Village provided useful information on the capturing techniques and old records on bears. Mr. S. Shibano of UF in Hokkaido, supported me for two years in the field works and provided useful techniques to take care of the bear.
The staff of UF in Chichibu, Messrs. H. Sawada, K. Ohmura, T. Saito, Ms. T. Harada, Ms. A. Ishihara, Messrs. Y. Igarashi, T. Chishima, H. Tashiro, S. Ohata, T. Ogawa, Y. Ohmura, T. Kamizuka, Ms. K. Sawato, Dr. H. Kabaya and Mr. K. Sasaki, all helped in the field works and equipment procurement. Messrs. S. Negishi, S. Ohmura, M. Hagiwara, and Ms. K. Ohata helped me in the management of the fund.
Messrs. H. Machida, G. Yamamoto, H. Suzuki and Ms. A. Kameyama helped me in the field works. I sincerely thank them all for their support to perform the research.

References
Hashimoto, Y. 1995. Food habit of Japanese Black Bear (Ursus thibetanus japonicus) in Chichibu, Thesis of Masters Degree, Over graduate School of Agricultural and Life Sciences, University of Tokyo. 35 pp. +XIV. (In Japanese with English summary)
Hazumi, T. Japanese Black Bear. Handbook of Japanese Animals 1, Heibonsha, Tokyo: 14-146.*
Ishida, K. 1995. Food habit and characteristics of the life history of Japanese Black Bear. *
Ishida, K. & Hashimoto, Y. (In preparation-a) Japanese Black Bear Body conditions and masting of beech family trees.
Ishida, K., Hashimoto, Y., Ohmura, K and Saito, T. 1994. Effects of the road construction on the wildlife in Tokyo University Forest in Chichibu IV; hunting, acorn harvest and Japanese Black Bear population. Transactions Jpn. For. Soc. 105: 557-558.
Ishida, K., Ohmura, K. & Sawada, H. 1991. Effects of roads to the wildlife in Tokyo University Forest in Chichibu - behavioral patterns suggested by tracks on the snow. Transactions Jpn. For. Soc. 102: 309-310.
Ishida, K., Yamanaka, R., Hashimoto, Y. , Shibano, S., Ohmura, K. & Sawada, H. (In preparation-b) Trapping of Black Bear in Chichibu, central Japan.
Ishida, K., Yamane, A., Akaiwa, T. & Igarashi, Y. 1993. Distribution of Japanese cerow Capricornis crispus and Sika deer Cervus nippon in Chichibu mountains. Bull.
Kaji, M., Sawada, H., Sasaki, K., Ohmura, K. & Ohkubo, T.1992.
　 Kelly, D. 1994. The evolutionary ecology of mast seeding. Trends in Evolution and Ecology 9(12): 465-470. *
　 Miguchi, H. 1995. Present terminus in the researches of masting Beach. Bull. Pop. Ecol. Soc. 52: 33-40.*
Miura, S. & Hirano . S. 1999. How many Japanese Black Bear should be exist, of demographical minimum viable population size. Seibutsu Kagaku, Tokyo 50:
Ohkubo, T., Kaji, M. & Hamaya, T. 1988. Structure of primary japanese beech (Fagus japonica MAXIM.) forests in the Chichibu Mountains, central Japan, with special reference to regeneration processes. Ecol. Res. 3: 101-106.
University Forests, University of Tokyo (UFUT). 1998. Memoir of Nature Researches in the University Forest in Chichibu, Tokyo, 368 pp..
University Forest in Chichibu. 2000. An out
(* in Japanese, ** in Japanese with English summary)

Table 1 13 barrel trap locations
------------------------------------------------
area t.no. site name terrain altitude
-------------------------------------------------
01 Kudonosawa slope 900 m
Taki- 02 Migurosawa ridge 780
kawa 03 Takadaira slope 1000
* 04 Namesawa ridge 1000
05 Wasabizawa slope 1120
06 Sawagoya slope 1150
07 Takadairataigan slope 900

11 Iriyama ridge 1000
Iri- 12 Yatake slope 1100
kawa 13 Toyaone slope 1100
14 Horiwari slope 1140
15 Akasawa ridge 1180
16 Akagisawa ridge 1220
-----------------------------------------------
*, The national road was constructed in Takikawa area.

　Table 2 . Number of bears of each
capturing status in each area.
----------------------------------------
Takikawa* Irikawa
year nwcp recp nwcp recp total*2
----------------------------------------
1991 3 - 0 - 　 3
1992 6 0 10 0 16
1993 2 2 4 5 13
1994 5 3 3 3 14
1995 5 3 2 4 14
1996 0 6 6 5 17
1997 3 3 3 5 　 14
1998 3 3 2 1 　 9
1999 4 1 0 1 6
----------------------------------------
Abbreviations, nwcp=newly captured; recp=recaptured;
fem.=female
*, The national road was constructed in Takikawa area.
*2, Individual numbers of each year or area. As there
were bears caught in both area at one year, the
total number is not the same as the sum of the
left four individual numbers.

　Table 3 . Number of bears each sex
caught in each area.
----------------------------------------
Takikawa* Irikawa
year fem. male fem. male total*2
----------------------------------------
1991 2 1 0 0 3
1992 4 2 3 7 16
1993 4 0 3 6 13
1994 5 3 2 4 14
1995 5 3 1 6 14
1996 2 4 3 8 17
1997 3 3 4 4 14
1998 1 5 1 2 9
1999 3 1 1 0 6
----------------------------------------
Abbreviations, fem.=female
*, *2, See the notes of Fig.2

Captions of figures

Fig. 1 Location of study area.

Fig. 2 13 locations of 15 bear traps at 13 sites.

Fig. 3-1 The outline of the home rages of females in 1994.

Fig. 3-2 The outline of the home rages of females in 1995.

Fig. 3-3 The outline of the home rages of females in 1996.

Fig. 4 The outline of home rages of a male and a large distance movement records of two males. Location of national road route 140 is also shown.

Abstract
To clarify the condition of and to estimate the effect of national road construction on the Black Bear population around the road, bears were caught with barrel traps with a bait of beehive. The body sizes were measured and the body conditions recorded. A part of larger adult bears were attached a collar transmitter and their home rages were traced roughly. 58 individuals were caught in 136 times during the 1991-1999 seasons.
Average density of breeding female was estimated as one bear per 7 to 8 square kilometers within the University Forest in Chichibu, Saitama, central Japan. Trapping results in neighboring areas of Takikawa (national road) and Irikawa (with small mountain road) were compared, and there seemed to be a temporal negative effect on the population by the road construction. I suppose bear population reservation in this area is partly supported by the tunnels as corridors.