I observed the use of vertical stratification of woods by two species of voles, Clethrionomys rufocanus bedfordiaeandC. rutilus mikado, and by three species of mice, Apodemus speciosus ainu, A. peninsulae giliacusandA. argenteus, in four different types of woods in Hokkaido, Japan. I set containers in the woods inside which a piece of bait was placed, including minute pieces of colored indigestible plastic, which were separated by color in each of four strata (under the litter, on the litter surface, and 50 cm and 150 cm in height above the litter), and at the same time performed live-trapping on the ground surface. All the faeces dropped in traps were then collected and analyzed to estimate the degree of vertical space use. All species but one used all four strata of habitats, but the vertical niche width (H') was narrowest inC. rufocanusand widest inA. argenteus, with subequal and intermediate widths inC. rutilusandA. speciosus. Data ofA. peninsulaewere insufficient to estimate the use of strata. As to habitat preference, C. rufocanusappeared in all four habitats, C. rutilusin three, A. speciosusin two, and the remaining two in one habitat. These trends of habitat preference agreed with those found in Hokkaido to date.
For a study of coexistence system in two red-backed voles, Clethrionomys rufocanus bedfordiae (THOMAS) andC. rutilus mikado (THOMAS), seasonal changes of food habits, biomass of plants, population density and microhabitat selection were examined. Food habits of these two species were similar from May to October, when plant biomass was richest. In the season when the common available foods decreased, C. rufocanusobviously changed its staple food item to the other one, whereasC. rutilusprincipally kept its food habits unchanged. These tendencies were not influenced by population density or microhabitat selection of the two species. In conclusion, C. rufocanushas a wider food niche than doesC. rutilus, and this condition may partly explain the frequent coexistence of the two species.
Litter size of the small Japanese field mouse, Apodemus argenteus, was examined in relation to its population fluctuation in a natural mixed forest of Hokkaido. Overwintered females had a slightly higher litter size than did current year's females, although the difference was not significant. There was a significant positive relationship between litter size and body size ; the correlation coefficient obtained for current year's females was higher than that for overwintered females. There was a significant negative relationship between litter size and population density ; a higher correlation was detected for overwintered mice than for current year's mice. Pregnant females were captured only in the increase phase, except for a few in the decline phase in May of 1979. Litter size significantly varied from year to year. Higher litter sizes were closely associated with the autumn breeding, a prolongation of the breeding season related to the population cycle.
In this study, bodies of the recent wild boars were measured, and the following five external measurements were analysed to presume their physical constitution. The body weight without viscera averaged 37.5 kg (range, 6.0-100.0 kg) in the male, 27.1 kg (range, 6.0-75.0 kg) in the female. The average of the head and body length was 106.0 cm (range, 60.0-151.0 cm) for the male, 99.2 cm (range, 60.0-135.0 cm) for the female. The withers height was 58.0 cm on an average (range, 32.0-85.0 cm) in the male, 54.0 cm (range, 33.0-78.0 cm) in the female. The average of the tail length was 13.6 cm (range, 6.5-22.0 cm) in the male, 12.6 cm (range, 7.0-19.5 cm) in the female. The average of the ear length was about 8.0 cm (range, 5.0-11.0 cm) for both sexes. Next, the wild boars used were divided into the juvenile group with a pair of the deciduous canines, and the adult group with a pair of the premanent ones. In the juvenile group there was no significant difference between both sexes in the measurements except for the head and body length, although in the adult group a significant sexual difference (p<0.01) was present. At last, based on the linear regression and the allometry formulae, it seems possible to estimate the physical constitution using the measurement of each character.
Scanning electron microscopical observations were performed to investigate the ultrastructure of the lingual papillae and the real surface of the dorsal tongue epithelial cells in the Japanese house bat, Pipistrellus abramus. Filiform papillae were distributed over the entire surface of the tongue except for the narrow radix zone. Some different types of filiform papillae were distributed in restricted areas of the dorsal surface. Fungif orm papillae were scattered among these filiform papillae. Higher magnification of the dorsal tongue epithelium revealed that prominent microridges and distinctive elevation of the cell border occurred widely in the basal area of the filiform papillae, interpapillar area and radix area. On the epithelial surface of the upper part of filiform papillae, only fine pits (micropits) were found.
Food and feeding behaviour of the introduced Formosan squirrel (Callosciurus sp.) were studied in Nogeyama Zoo, Yokohama City, Kanagawa Prefecture, Japan, from August 1981 to July 1982. Throughout the field observations, various parts of 29 species of trees and one species of fungus were used as food. The main food trees wereCastanopsis cuspidate, Prunus (Cerasus) spp., Morus austraris, andAcer palmatum. Various parts of these food trees were eaten depending on season : mainly fruits and cones in autumn, bark and bubs in winter, bark and flowers in spring, and fruits and cones in summer. The cumulative frequency of feeding per tree over a year was high on the tree species which produced mainly fruits or cones. It should be noted that the squirrels changed their feeding behaviour depending on the kinds of food. Adaptability to the wide range of foods and ability to change the food habit are thought to be the factors which made this species possible to settle outside their native habitats.
A faunal survey of bats in Osorezan district, Aomori Prefecture in 1979-1982, revealed inhabitation of the following eight species belonging to five genera; Rhinolophus cornutus cornutus, Rhinolophus ferrumequinum nippon, Myotis hosonoi, Myotis frater kaguyae, Myotis macrodactylus, Vespertilio superans, Pipistrellus endoiandMurina silvatica. Among them, P. endoiconstitutes a new record in Aomori Prefecture.My. hosonoiandMu. silvaticawere the most common species in this district. Dominant species differed with different study areas. Most of the specimens ofP. endoiandMy. macrodactyluswere caught over rivers. In forests, the f aunal composition and the number of bats were poor. The activity of bats in summer showed one large peak between the times of 19: 00 and 21: 00 and two small peaks between 22: 00 and 23: 00 and between 4: 00 and 5: 00. It seems that the following six species were lactating in mid-August ; R. c. cornutus, My. hosonoi, My. f. kaguyae, My. macrodactylus, P, endoiandMu. silvatica. Newly weaned young of the following four species had foraging flights in mid-August; My. hosonoi, My. macrodactylus, P. endoi and Mu. silvatica.
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