Mammal Study

The seasonal variation in home range size of one male and one female Iriomote Cat Prionailurus bengalensis iriomotensis was studied by radio-tracking and automatic photography on Iriomote Island, Japan. The study was conducted in the Shirahama area located in the western part of the island. Shirahama provides a small area of suitable lowland habitat (<50 m a.s.l.) for the Iriomote Cat. Two individuals, one male and one female, were confirmed to be resident in this area. The periodical home range size of the male was 1.24 ± 0.41 km² and that of the female was 1.30 ± 0.54 km² throughout the year, with no significant difference between them. We compared the results of these observations with those from another area of suitable habitat in Funaura and discussed what factors may affect male home range size. The home range of the male cat in Shirahama was found to be only half the size of that of males in Funaura, though it showed similar seasonal fluctuation. The home ranges of females were similar in the two areas. Our results provide empirical confirmation of the influence of the number and distribution of females on male home range size in a solitary felid.

The seasonal and daily activity patterns of 15 Japanese badgers (Meles meles anakuma) were studied using radio-telemetry and a video monitoring system from April 1997 to March 2001 in Yamaguchi City, Western Honshu, Japan. The badgers were primarily nocturnal, and there were no differences between the daily activity patterns of males and females. The badgers were sometimes active in the daytime; breeding females, in particular, would often forage during the day, in spring. Between July and October, they usually emerged from their setts around sunset and returned around sunrise. The time between emergence and return became shorter after November. From January to February, most activity ceased, and the badgers stayed in their setts most of the time. Time spent outside the sett was longest in summer and autumn. Activity of Japanese badgers seems to be influenced by the day-night cycle, reproduction, temperature, and food availability.

The process of obtaining breeding territories and mating success in male northern fur seals was studied through a longitudinal survey in St. Paul Island, Alaska in 1993–1999. Resighting of metal tags that had been deployed to pups in their natal areas generally showed site fidelity of males to natal breeding areas, but also indicated movements within the breeding area. Males started to reside in the periphery of central breeding areas (CBAs) at age 7, and some males established breeding territories in the CBAs at age 7–9. Males bleach-marked in the peripheral areas showed a tendency to reappear in the same locations over successive breeding seasons. Some of them entered nearby CBAs in the late breeding season and held territories. Once adult males acquired breeding territories, they exhibited a strong tendency to return to the same locations in the following breeding season(s). Duration of the effective territory tenure after June 30 and the maximum number of adult females in a male's territory did not differ significantly between the first and second years of his territory tenure (P > 0.05). However, starting date of territory tenure became earlier in the second season (P = 0.04). The index of mating success estimated from the seasonal frequency distribution of copulations also increased significantly in the second years of territory tenure (P = 0.03). These results indicate that territory acquisition is a site-specific multi-year process in which males return to the same breeding area for successive breeding seasons and gradually shift their presence spatially to the center of the breeding aggregation and temporally to the peak season of female estrus. Prior experience formed through site fidelity is likely an important factor for territory acquisition and mating success in male northern fur seals.

It is particularly difficult to distinguish between M. ikonnikovi and M. mystacinus based on external taxonomic characters because of their extreme similarities in morphology. Although they may be distinguished easily based on their skulls, it is not permitted to take specimens for identification because M. ikonnikovi is classified as threatened and endangered and M. mystacinus is classified as threatened and vulnerable, by Japan's Ministry of the Environment. The authors describe an entirely new method of identifying live individuals based on an external character, in particular the pattern of the blood vessels visible in the tail membrane: in M. ikonnikovi the main blood vessel forms a ‘Dog-leg type’, whereas in M. mystacinus it forms a ‘Straight type’.

Factors affecting body temperature (Tb) fluctuations in winter were examined in Korean field mice Apodemus peninsulae. Animals were maintained under the following three conditions to mimic autumn followed by winter, plus two modes of behaviour, solitary and grouped, in winter: 1) short day (8 Light:16 Dark) at 25 ± 2°C and solitary, for 12 weeks towards the end of which their Tb was recorded; 2) constant darkness (DD) at 4 ± 2°C and solitary, for a week; and 3) DD at 4 ± 2°C and in groups (two or three animals in a cage), for about 10 days. Using implanted data loggers Tb was monitored in 13 mice that were exposed to these three conditions in sequence. When the animals' body temperature was below 30°C, it was assumed that they were torpid according to the bimodal pattern of minimum daily Tb. The maximum period of daily torpor was 390 min/day, and torpor was exhibited by seven of the thirteen animals exposed to conditions-2) and -3). Since torpor was found in one mouse even under condition-1), without any environmental stressors, it is suggested that this species is prone to spontaneous daily torpor. Cohabitation tended to synchronize Tb fluctuations irrespective of the state of the animals, torpid or not. Thus, this species may aggregate and synchronize torpor and/or Tb fluctuations to reduce heat loss during winter.

We assessed the original and recent distribution of sea otters (Enhydra lutris) along the coast of Hokkaido, Japan, based on information of remains from archeological sites, old hunting records, and records of recent sightings obtained from interviews. Some remains, including pups from one archeological site, suggested the possibility that some small aggregations had historically been distributed around Hokkaido. However, sea otters seem to have disappeared prior to commercial hunting in the 18th and 19th centuries, as no records could be found documenting the hunting of otters around Hokkaido during that period. Since 1973, intermittent sightings of otters have been made around Hokkaido, and since 1996, the sighting frequency has increased. Between 1962 and 2001, 119 sightings and six dead otters were recorded around Hokkaido. The source population of these otters is probably in the Habomai Islands of the southern Kurils. However, due to increasing anthropogenic habitat disturbance, it is unlikely that a stable habitat for sea otters can be established in the coastal waters of Hokkaido.

Univariate and multivariate statistical analysis of 14 skull, dentary and dental characters and five external characters recorded from 78 specimens of Mus musculus indicated the occurrence of two distinct forms in southern and eastern Indonesia. The two forms were distinct from Mus musculus domesticus in Western Australia.

The more widespread form was attributed to M. m. castaneus which occurred on Bali, Lombok, Flores, Lembata, Alor, Kai, Banda, Neira, Timor and Roti islands. The other form all of which are new record for the reason from Kisar and Tanimbar Islands (which represent new distributional records for Mus musculus), differed consistently from M. m. castaneus. Descriminant Function Analysis (DFA) using a reduced set of five skull, dental and external characters correctly allocated 98% of individuals to their appropriate form; bulla length, C¹M³ length and M¹ length were important discriminants between the two forms.

Unlike local populations of Western Australian M. m. domesticus, which morphologically differed significantly, the island populations of the widespread M. m., castaneus did not appear to differ significantly.