A case of a Yezo brown bear, Ursus arctos yesoensis, having four fetuses in a litter is reported for the first time, together with another case with two fetuses. The four fetuses of a litter were a male and three females supposed to be 6.5 months after fertilization and two fetuses of the other litter were females near birth. There was great difference between the two litters in the degree of their growth and development; the fetuses 6.5 months old were about 20 g in body weight, had no hair on the body, and had no eyelid clefts; while, the fetuses near birth were about 300 g, had dense hairs on the body, and had eyelid clefts. Fetuses of the bear seem to grow rapidly during the period of the last one month before birth.

View full abstract

Seven hundred and sixty four voles, Clethrionomys rufocanus bedfordiae (THOMAS), taken from the Ishikari Plain, Hokkaido were aged for the variation study on the pattern of the third upper molar. Complex molar pattern with a fourth inner salient angle was found in about 4.1 per cent of young individuals without molar roots. Simple molar pattern without the fourth salient angle varied in shape with advancing age, i.e., the decrease in the posterior lobe of crown pattern. The seasonal variation of the molar pattern was attributed to that of the age composition of vole population.

View full abstract

This paper describes the local distribution of alien rats and rodents, Rattus rattusandR. norvegicus, on Chichijima and Hahajima, and discusses briefly potential damages to avifauna from those rodents. At Chichijima, R. norvegicushas probably become extinct.R. rattusis likely to be ecologically balanced on both islands, and birds do not seem to be its prey. The metacestode of cat parasiteTaenia taeniaformisfrom a rodent's liver proved that cats were widespread on both islands. Cats are also an important avian predator.

View full abstract

Habitats and habits, especially food and nests, of roof ratRattus rattuson Torishima are discussed in relation to its possible damage to endangeredDiomedea albatrus. The rats inhabit mainly the northwest grassy area of 0.7 km². Evidence of their existence was also found in poorly vegetated nesting area ofD. albatrus. Predominant vegetations were herbs and grasses less than 50-60cm tall. Though essentially arboreal or semi-arboreal, the rats were active on the ground, and seemed to nest mainly in volcanic ash, modifying the burrows of crabs. Leaves, stalks, seeds and other plant materials (88.6% in vol.) formed their main food. However, this simple flora and its crop are affected by such single factor as the weather. When the leaves die out, the rats would attack albatross chicks.

View full abstract

1. Reproductive activity of the Japanese shrew-mole, Urotrichus talpoides, was investigated by mark-release and removal methods in the University Forest in Chiba, University of Tokyo from April 1975 to July 1979. One livetrapping plot (L plot) and several snap-trapping lines (S lines) were set up in the mixed forest.
2. The testis length of sexually active males was more than five mm, and the weight of active males mostly exceeded 14g. Breeding females were usually heavier than 13g.
3. Males became sexually mature in early February, and in May, active males rapidly decreased. Matured females were mainly observed in February and March, pregnant females, in March and April, lactating females, in April and May. The current year's young became captured in April, and did not attain sexual maturity until the following spring. These seasonal changes of reproductive phase were relatively constant from year to year.
4. On L plot, the percentage of active males to the total adult males reached 100 every year during the study period, and among resident adult females, the percentage of lactating individuals was 83.3-100.0.
5. Estimating from the results of live-trapping, gestation, lactation and the period from parturition to independence of the young were all about four weeks.
6. The mean litter size was 3.6 (N=8) .

View full abstract

A faunal survey of mammals of Awashima Island was carried out during December 17-20, 1980. Awashima Island lies in the Japan Sea about 20 km off the western coast of the northeastern Honshu, Niigata Pref, and has an area of 9.5 km².
There were obtainedUrotrichus talpoides, Crocidura dsinezumiandApodemus argenteus. To add to these three species, Mogerasp. andMustela sibiricawere sure to inhabit on Awashima Island. Although it was the most abundant small mammal species on the opposite Honshu or adjacent Sado Island, Apodemus speciosuswas not found on Awashima Island.
Urotrichus talpoidesof Awashima Island had larger body weight than that of the opposite Honshu, Murakami City.

View full abstract

To compare the climbing ability of two Apodemus species, A, argenteusandA speciosus, horizontal bar walking test, vertical bar climbing test and gap crossing test were made in an experimental cage from 27 September to 14 November 1980.
In the horizontal bar test, A. argenteuscould walk quickly on all bars of various diameter (0.25-16.30 mm), whileA. speciosuscould not do on small bars of diameter less than 1.20 mm. In the vertical bar test, A. speciosuscould not climb up and down any kind of bars. In the gap crossing test, there was little difference in ability between two species.
Theses differences in climbing ability between twoApodemusmight be related with their differentiated modes of life in natural habitat.

View full abstract

The rectal temperature of four Japanese serow (Capricornis crispus) was measured every morning (8: 00) and evening (15: 00) .
1. Rectal temperature was correlated with air temperature higher in summer (38.36°C at 8: 00, 38.73°C at 15: 00), lower in winter (38.21°C at 8: 00, 38.36°C at 15: 00, Table 4) .
2. Rectal temperature was generally higher in the evening than in the morning, with the differences of 0.15-0.32°C.
3. Rectal temperature seemed to become lower as the serow became older (Fig. 2), which must be confirmed by future measurement.

View full abstract

The average herd size of Sika deer (Cervus nippon) on Kashima Island (SW Shikoku, Japan) whose vegetation is dominated by evergreen broad-leaved forests was only 1.28 deer/herd. This value is apparently smaller than those recorded in northern Japan which belongs to the cool-temperate zone and is covered by deciduous broad-leaved forests.

View full abstract