Food Habits of Japanese Serow (Capricornis Crispus) in the Western Foothills of Mt
J. Mamm. Soc. Japan 20 (2) : 151-155 December 1995
Short Communication
Food Habits of Japanese Serow (Capricornis crispus) in the Western Foothills of Mt. Zao, with Reference to Snow Cover
Seiki TAKATSUKI, Yuko KOBAYASHI-HORI*t and Takeo ITO*
Laboratory of Wildlife Biology, School of Agricztlture and Life Sciences, The University of Tokyo, Yayoi 1-1 -1, Bzinkyo-ku, Tokyo 113, Japan * Depal.tment of Biology, Faculty of Education, Yamagata University, Yamagata 990, Japan (tPresent address : Takamatsu Primary School, Yonezawa 643-2, Sagae, Yamagata 991, Japan) (Accepted 26 August 1995)
In a previous paper, we reported a comparison of the winter and summer diets of the Japanese serow (Capricornis crispus) living in the western foothills of Mt. Zao, northern Japan (Takatsuki et al. 1988). Their winter diet was character- ized by the predominance of evergreen shrubs such as Cephalotaxus harringtonia var. nana and Aucuba japonica var. borealis, which grow abundantly on the floors of deciduous forests in this region. The northeastern part of Honshu (the main island of Japan), including the study area, is a center of this serow's distribution and its population is most abundant there (Furubayashi et al. 1979). This region experiences snowy winters, which must directly affect the ecology of the serow. The objective of this study was to examine the year-round diet of the Japanese serow during a year which included an exceptionally snowy winter. This unusual opportunity afforded a chance to consider the signifi- cance of snow which serows must get rid of.
Materials and Methods
Since the study area and methods have been described previously (Takatsu- ki et al. 1988), they are only briefly mentioned here. Fecal pellets were sampled, as described by Takatsuki et al. (1988), on the north-facing slope (600- 700 m in altitude) of Mt. Ryuzan (1,362 m), in the western foothills of Mt. Zao. The forest where fecal samples were collected, was dominated by Quercus serrata with undergrowth of evergreen shrubs such as Cephalotaxus harringtonia var. nana and Aucuba japonica var. borealis, and Sasa palmata, a dwarf bamboo. Many areas of this coppice forest have been planted with the conifer Cryptomer- ia japonica. Fecal pellets were collected six times between October 1983 and September 152 Takatsztki et al. 1984, and were grouped into four seasons according to plant phenology. Thirty pellets were sampled from each fresh dung pile, representing each defecation. Six dung piles were sampled in autumn (October 1983), seven in winter (February and March 1984), four in spring (May and June 1984) and five in summer (September 1984). Samples were washed through a 0.5 mm aperture sieve. The plant fragments retained were microscopically identified. Epider- mices from the major plants in the serow's habitat were prepared for reference. Plant fragments obtained from feces were spread over a glass slide with 1 mm grids, and the cross points covered by samples were counted at X 100 or x 300 magnitude (Stewart 1967, Taltatsuki 1978). Records of snow depth from 1982 to 1992 were obtained from the Yamagata Meteorological Station situated in Yamagata City (elevation 150 m), about 5 km northwest of the sampling area. Snow depth (accumulated depth of snow at each measuring time) was recorded to the nearest 1 cm three times a day(09 : 00, 15 : 00 and 21 : 00).
Results
Five plants, or plant categories, were identifiable by microscopic examina- tion: Aucuba japonica var. borealis, Ilex leucoclada, Cryptomeria japonica, Cephalotaxus harringtonia var. nann, Carex spp., and Sasa spp. Other frag- ments were grouped as "leaves of dicotyledonous plants", "unidentifiable coniferous leaves", "graminoid leaves", "non-leaf parts" (twigs and bark) and "other unidentifiable materials". Considerable seasonal changes in fecal compositions were observed (Table 1). The data for 1981 (Takatsuki et al. 1988) are also shown for comparison. Leaves of dicotyledonous plants presented as much as 47.8% of the diet in October 1983. Though most fragments were not unidentifiable to species, they showed characteristics of deciduous broad-leaves (e.g. poorly transparent epidermises and well-developed networks of veins). Cephalotaxus harringtonia var. nana accounted for 5.9%, and was the most commonly eaten dicotyledon found. In February/March of 1984, when snow was very deep, the proportions of Cephalotaxus harringtonia var. nana and Auczlba japonica var. borealis account- ed for only 4.2% and 0.9% of the diet, respectively, whereas in the winter of 1981 they represented 41.4% and 8.8%, respectively. Conversely, the plantation conifer Cryptomeria japonica was not found in the diet in the winter of 1981, but accounted for 10.8% in February/March 1984. Non-leaf parts, mainly consist- ing of twigs and bark, and dicotyledonous leaves mainly consisting of fallen deciduous tree leaves contributed as much as 40.9%, and 21.1% of the diet, respectively. These results indicate that serows were forced to eat these less nutritious foods in the snowy winter. In May/June, leaves of dicotyledo~isprovided up to 44.1% of the diet, while non-leaves declined to 18.1%. Aucuba japonica var. borealis increased to 6.8%, and Cryptomeria japonica provided 9.4% of the diet. Food Habits of Japanese Serozu 153
Table 1. Fecal composition (%) of Japanese serow in the western foothills of Mt. Zao, from October 1983 to September 1984. Data for 1981 (Takatsuki et al. 1988) are shown for comparison.
Oct. p~(Sept. I Mar. Aug. Leaves of dicotyledons Auczlba japonical Ilex leucoclnda C?ypt~nze?~iajaponica Cephalota~zlshawingtonia2 Unidentified conifers Sasa palmata Graminoid leaves NOII-leaves3 Others4 var. bo~enlis, var. nana, Includes twigs, bark and stems, Includes fruits, ferns and unidentified materials.
Fecal composition in September was similar to that in May/June, with leaves of dicotyledonous plants still very important at 50.8%. Cryptomeria japonica, however, decreased in significance while Sasa palmata and other graminoid leaves increased (Table 1).
Discussion
The decline in the proportion that evergreen shrubs, such as Aucuba japonica var. borealis, Cephalotaxus harringtonia var. nana and Ilex leucoclada, contributed to the diet of the Japanese serow in the winter of 1983/84 and the converse increase in Cryptomeria japonica (Table 1) suggest that while shrubs were buried under snow, and thus unavailable to serows, the needle leaves of C. japonica remained above the snow and were thus available. Leaves of dicotyledonous plants contributed more to the diet in the 1983/84 winter than in 1981 (Table 1). Epidermal features indicate that they were most probably the dead leaves of woody plants such as Quercus spp. Stomach content analysis of serows shot in the winter of 1994 in an area close to the present study area also revealed the presence of similar dead leaves (Takatsuki et al. unpublished). It may seem strange that evergreen shrubs contribute less to the diet than the dead leaves of deciduous trees in snowy winters because the latter may be presumed to be on the ground and thus less accessible in snow. Dead leaves, however, are widespread in the serow's habitat and are thus far more widely available, while evergreen shrubs grew abundantly but only in certain places, and are thus less generally available in the whole area. In addition to Cryptomeria japonica, consumption of twigs and bark was 154 Takatsztki et al.
Table 2. Maximum daily snow depth (cm) from November to April for the winter of 19831 84, and for other winters from 1982 to 1992 (n=10). Nov. Dec. Jan. Feb. Mar. Apr. 1983184 20.0 6.0 46.0 77.0 70.0 27.0 Other Winters 4.1 18.0 29.5 35.4 21.6 0.3 SD 3.6 11.7 11.4 7.7 10.8 0.9 also greater in the 1983184 winter than in the 1981 winter. Serow seem not, however, select twigs and bark, but take them incidentally while eating dor- mant buds. The winter of 1983184 was exceptionally snowy when compared with ten other winters (Table 2). The maximum daily snow depth (the greatest value on a day in each month) was significantly greater then, than in other winters (Student's t-test, p<0.05 ) with the exception December 1983, when it was significantly less than in the other winters (p<0.05). Snow depth data were recorded at an elevation of 150 m, and snow depth in the high serow's habitat was in fact much deeper, for example in excess of 150 cm in February 1984. The present distribution of the Japanese serow corresponds with the distribution of deciduous broad-leaved forests, such as beech and oak, in the cool temperate zone (Furubayashi et al. 1979) though it should be noted that most native lowland forest, once habitat to serows, has been lost to develop- ment, and thus the altitudinal range of the Japanese serow is not entirely natural. These forests show a clear seasonality in plant growth, and hence a clear seasonality of forage supply for serows. Furthermore, winter snow accelerates the seasonality in forage availability, resulting in super abundance of food during the growing season and scarcity of food during the snowy season. Snow, in turn, serves to protect plants from the cold and from dessicating winds which are disastrous for them. Snow helps to keep the anbient tempera- ture constant at around 0 "C. Miyawaki (1987) has in fact shown that abundant growth of evergreen shrubs, including Cephalotaxus harringtonia var. nana, Daphniphyllum macropodum var. humile, Ilex leucoclada and Aucuba japonica var. borealis on the forest floor is favored by snow cover. Winter forage availability for serows in northeastern Honshu seems to be similar to or even greater than, in the less snowy areas of the Pacific side of northern Japan. Evergreen shrubs are, in fact, important foods for the serow in this area (Takatsuki et al. 1988), as they are in similar habitats in central Japan (Takat- suki and Suzuki 1985). If snow becomes so deep, however, that it buries these shrubs, forage availability abruptly.declines, and must cause serious food shortages for serows. Dependency on Cryptomeria japonica as foods in the winter of 1983184 was significantly greater than in winter 1981 (Table I), but since this tree is a planted species that is uncommon under natural conditions, it cannot be an "emergency snowy winter food" for serows living under a natural conditions. Some evergreen conifers such as Pinus densiflora, P. Food Habits of Japanese Se~ozv 155 parviflora and Thuja standishii grow naturally in habitats similar to the shady area, but they are found only in small patches, or on ridges (Miyawaki 1987). It seems unlikely, therefore, that serows can subsist on conifers under natural conditions. The unpredictability of forage availability, as a result of variance in snow cover, is a key point in our understanding of the ecology of the Japanese serow in such snowy areas.
Acknowledgments
This work was supported in part by the Grant-in-Aid from the Ministry of Science, Culture and Education (No. 58740304).
References
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