Applicability of seven primer sets, originally designed for polymerase-chain-reaction (PCR) amplification of microsatellite DNA in the gray-sided vole, Clethrionomys rufocanus, was examined in other 12 microtine species from three genera (Clethrionomys, Eothenomys and Microtus). Of the primer sets used, one distinctly amplified PCR products in all the species examined. Three sets gave PCR products in all but one species. The remaining three sets failed to amplify any products in several species. Non-amplification occurred mostly in Microtus species, although two primer sets were not available for two Clethrionomys species. Since most amplified loci showed allelic variations, the present primers are useful for molecular ecological studies of related microtines, especially Clethrionomys and Eothenomys species.

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Aggression and the use of vertical and horizontal space in the presence of con- or hetero-specific individuals were investigated in laboratory for Sorex unguiculatus, S. caecutiens, and S. gracillimus in Hokkaido, Japan. S. unguiculatus frequently used the below floor strata of experimental cages or subterranean burrows as their main area of activity, whereas S. caecutiens and S. gracillimus mainly used the cage floor or the ground surface. The presence of con- or hetero-specific individuals led to no changes in any of the three species in the use of space, or in behavioral patterns (active/inactive ; underground/resting/ moving on the ground surface). When two individual shrews were introduced into two interconnected cages, they tended to remain in separate cages, with the exception of S. gracillimus with a conspecific. Dominance rank was highest in S. unguiculatus, intermediate in S. caecutiens, and lowest in S. gracillimus. S. caecutiens attacked S. gracillimus most frequently and S. gracillimus received attacks from S. caecutiens most frequently. The implication of this research is that severe interference competition may occur in the field between S. caecutiens and S. gracillimus.

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The structure of small rodent communities, in both natural forests and young plantations, in the Asahikawa region of Hokkaido, Japan, in relation to the effects of long-term and large-scaled forestry, was analyzed using census data spanning the 31 years from 1962 to 1992. Rodent communities in both natural forests and plantations consisted largely of four species : Clethrionomys rufocanus, C. rutilus, Apodemus argenteus, and A. speciosus. Clethrionomys rufocanus was found to be dominant in both habitats, however the relative abundance of species differed significantly between habitats. Although the dominancy of C. rufocanus was most obvious in forestry plantations, the proportion it contributed to the community decreased during the 1980s. Conversely, Apodemus species have increased in both habitats over the same period. Rodent species diversity has increased in the last decade. The decline in the proportion of C. rufocanus has occurred in parallel with the decrease in the area of land under forestry plantation, which is the preferred habitat for C. rufocanus. These findings indicate that monocultural habitats, such as forestry plantations, may support super dominant species such as C. rufocanus, which results in an impoverished rodent community, in terms of species diversity.

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A technique for age determination based on the dry weight of the optic lens was tested in Smith's red-backed vole, Eothenomys smithii. The model equation W=a+blog₁₀A (W : lens weight in mg, A : age in days, a and b : parameters to be estimated from data) was applied to our data from 65 known-age laboratory-reared voles. As a result, the predicted age in days (Â) at a given lens weight (W) could be calculated from the equation Â=10^{(W+1.415)⁄2.131}. For example, an individual with a lens weighing 3.22 mg was estimated as having a predicted age of 150 days, and the 95% confidence interval at 150 days was calculated to be 17 days (142-159 days, or 11.3% of the predicted age) for the mean prediction and 144 days (94-238 days, or 96.0% of the predicted age) for the individual prediction. Lens weight can, it appears, provide the best age criterion at present, particularly in rodents with rootless molars such as E. smithii.

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Both postnatal growth and development of Japanese field voles, Microtus montebelli, were observed in a laboratory colony. Details of the developmental aspects of the life-history of this species are described focusing on behavioral development including ultrasonic vocalization, sexual dimorphism and the use of sigmoidal models of growth patterns. One purpose of the study was to provide a reliable basis for age-estimation of a wild population prior to conducting field investigations. The overall pattern of development of M. montebelli was similar to that of other Microtus species, particularly in their relatively rapid development. Young M. montebelli were found to vocalize intensively at an ultrasonic frequency of approximately 25 kHz until their eyes opened. The Gompertz equation was selected from three nonlinear growth models (Gompertz, logistic and von Bertalanffy), as it best described the curves of body mass increase and of four external lengths, and it best estimated maximum growth rates derived from the Gompertz equations fitted to actual rates during a linear growth phase. These features of the Gompertz equation seemed to be useful for analyzing growth patterns of wild voles. After 30 days, growth curves for each morphometric parameter diverged sexually, thus, weight-classes used for age estimation should differ between the sexes.

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In order to solve traffic problems and to understand possible epidemic risks resulting from the feeding of wild red foxes, Vulpes vulpes, the acquisition of food begging behavior by foxes in the Shiretoko National Park, Hokkaido, Japan was studied. Foxes were individually identified and their behavior was observed from June to October each year from 1992 to 1994. The locations of family territories and denning sites were established, and the degree of their tolerance to humans was investigated, and the relevancy of these factors in food begging behavior was examined. The development of food begging behavior among individuals less than one year old was strongly correlated (p<0.01) with their dens being within 20 m of the road edge. Most juveniles which were not born in dens near the roadside showed no food begging behavior and most individuals more than one year old, which had not previously shown such behavior did not acquire it at all, strongly suggesting that food begging behavior was predominantly acquired by juveniles denning near roads. Thus, preventing foxes from denning near roads should be an effective means to obstruct the acquisition of begging behavior.

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I determined the age of sexual maturity in Japanese giant flying squirrels, Petaurista leucogenys. The degree of testicular development was estimated in 25 males 224 times during eight years. The scrotum began to extend at the age of 7.5-8.5 months, and was slightly swollen in males 8-13 months old. Testes of 1⁄2-3⁄4 size were observed in males from 14 months onward. By the mating season when they were 21-22 months old, the proportion with full-sized testes was 57% of the males. All five males of 27-28 months of age had full-sized testes. One 22 month-old male and one 27 month-old were observed copulating. Summer-born males had slightly faster developing testes than spring-born males. None of 19 young females were observed in estrus. The attainment of sexual maturity in males at 21-22 months of age seems very late as the intermediate-sized rodents. It is suggested that mothers allow their young to remain with them for 1-1.5 years until they become sexually mature in order to increase the survival rate of their young, thereby compensating for their small litter sizes of one or two.

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We excavated a breeding nest of the Daurian pika, Ochotona daurica, in central Mongolia. Four young were captured within the burrows. Three food storage chambers contained plant fragments and a large amount of fecal matter, indicating that hoarded food had been consumed during the last winter. The nest chamber was spherical and measured 22×18×21 cm. Most of the nest chamber was filled with piles of grasses, and these piles were presumably their resting site. The burrow system had three entrances, and the nest chamber was connected to three burrows. Multiple nest entrances were provided ready access to refuge for pikas active on the ground surface from aerial and terrestrial predators, while multiple burrows also provide refuge against the intrusion of predators such as stoats into nest chambers.

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Roosting, foraging and reproductive aspects of two species of dog-faced fruit bats, Cynopterus brachyotis and C. horsfieldi, were examined in Ulu Gombak, Selangor, West Malaysia. The day roosts of C. horsfieldi were sparsely distributed and were found mainly in palms, whereas roosts of C. brachyotis were abundant, and mostly found in non-palm tree species. Males of both species frequently changed their roosts. The nocturnal activity patterns of the two species were different. The initial peak of flight activity of C. brachyotis was two hours sooner after sunset than that of C. horsfieldi, and its flight activity gradually declined during the night. In C. horsfieldi flight activity decreased around midnight then increased again three hours before sunrise. The home ranges of C. horsfieldi were larger than those of C. brachyotis, however these were non-exclusive ranges with individual home ranges of both species overlapping extensively. In association with their greater home range size, C. horsfieldi also tended to move further than C. brachyotis (when comparing means of greatest distances moved). The diets of the two species also differed, with C. brachyotis eating fruits, flowers and leaves, whereas C. horsfieldi ate Ficus fruits virtually throughout the year. The wet weight of figs carried by C. brachyotis per feeding bout averaged 7.9 g, while C. horsfieldi carried on average 17.8 g of figs. The average distances between feeding roost sites and fruiting Ficus variegata trees were 50-78 m. Cynopterus brachyotis probably produces two or three litters per year whereas C. horsfieldi has two litters.

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