Mammal Study

The Iriomote cat is an endangered subspecies (CR on the Japanese Red List) found only on Iriomote-jima Island in the Ryukyu Archipelago, Japan. One of the main factors threatening the Iriomote cat is the main paved road that contributes to traffic mortality of this wildcat and also alters its preferred lowland habitats with abundant prey. One of the reasons why the Iriomote cat appears on the road may be due to the presence of prey; therefore, we investigated road use by this wildcat in relation to its prey. In 2009, scat surveys were conducted to assess road use by the Iriomote cat, and prey surveys were undertaken in the morning and at night, mainly targeting terrestrial frogs and reptiles. To analyse the importance of factors related to road use by the Iriomote cat, the influences of prey density along road types, habitat types, presence or absence of road construction activities, and survey regions on number of scats were examined using nested generalised linear models (GLM), assuming Poisson error and a log-link function. Diurnal lizard density was strongly correlated with scat along roads, and the density of road-killed Fejervarya sakishimensis was positively correlated with scat presence along roads.

This study was performed to gain more knowledge about the Bohor reedbuck time budget and vigilance in a savanna habitat. Detailed data on the time-budget were collected through focal animal observation technique to determine whether the time budget activities of Bohor reedbuck was affected by vegetation cover and to test if herd size, position in herd, the age and sex affect vigilance efficiency. We fit generalized linear mixed-effect models to assess how herd size, sex, animal position in the herd and age affected individual time allocation to vigilance behaviour. The most parsimonious model averaging clearly showed how vigilance behaviour among Bohor reedbuck was strongly affected by age, sex, the total herd size and animal position in the herd accounting for the lowest value of Akaike Information Criterion (AIC). Vigilance and feeding behaviour occupied the largest percent of Bohor reedbuck daylight time budget. Herd size effects were significant on different behaviour categories only when the Bohor reedbuck was observed in sympatric association. Our findings support the herd size effect hypothesis only in sympatric grouping system. However, further study is needed to investigate the possible sex-specific functions and targets of vigilance behaviour with respect to the herd direction in the field.

The lamination of the masseter muscle was gross anatomically examined in the water deer (Hydropotes inermis). We could distinguish several layers such as the M. masseter superficialis, M. masseter intermedius, M. masseter profundus, M. maxillo-mandibularis, and M. zygomaticomandibularis, The M. masseter superficialis was subdivided into lamina prima and lamina secunda. The lamina prima originated from the facial tuber, facial crest, and zygomatic arch with a broad tendinous sheet. The lamina secunda arose from the posterior facial crest and anterior area of the zygomatic arch and was inserted to the mandible by a broad tendinous sheet. The M. masseter intermedius arose from approximately same origin as the superficialis lamina secunda by a distinct tendinous sheet. Moreover, only one part was confirmed in the M. maxillo-mandibularis and the M. zygomatico-mandibularis and only two parts in the M. masseter profundus pars posterior. Moreover, the most rostral part of the M. maxillo-mandibularis was inserted to the mandible by a small weak tendon. This result suggests that this muscle layer may not restrict the mouth opening more remarkably than that of cervids which develop the tendon. In this study, we could confirm the lamination of the masseter muscle with the simplified layers in the water deer.

The Pallas's squirrel (Callosciurus erythraeus) is one of the invasive alien species in Japan. Although control measures for this species have been attempted for a long time, the eradication has not succeeded and the populations continue to increase. To initiate control of the invasive alien squirrels as soon as possible, we have to detect their existence at low density stage soon after colonization. The Pallas's squirrels are known to use acoustic signals when encountering predators and during mating chases. We tested the effectiveness of playback surveys in monitoring the Pallas's squirrel. The squirrels were attracted by mobbing sounds in 63 to 83% of trials, and by mating sounds in 24 to 27% of trials conducted in Kamakura City where Pallas's squirrels had established 60 years ago. In 34 isolated woodlots of Iruma City where Pallas's squirrels has been introduced recently, we found the squirrels in two woodlots by direct observation, but detected in other three woodlots by playback surveys. The sound playback method appears useful to detect Pallas's squirrels even in low density situations.

We conducted point censuses in Yakushima island to estimate the density of Japanese macaque (Macaca fuscata yakui) males ranging alone, focusing on its vegetational, seasonal, and regional variation. In highland areas, the detection frequency of males ranging alone did not differ among different types of vegetation, despite the latter's effect on overall population density. The detection frequency of males ranging alone in the mating season was a third of that in the non-mating season. In the mating season, males exhibit strong cohesiveness with a group, probably in search of resident estrous females. Outside of the mating season, we detected 25% fewer males ranging alone in lowland areas, which have high population densities and strong inter-group competition, than in highland areas. The absolute density of males ranging alone was estimated to be 1.2–5.7 individuals/km². Meanwhile, the group and population densities were 1.25/km² and 19.3/km², respectively. A considerable number of males therefore remained outside of groups, and male cohesiveness with groups is flexible in relation to ecological and social circumstances.

The fecal pellets and fecal pellet group characters of two ungulates, the Japanese serow and sika deer, were compared in Tokushima, Japan, where the species occur sympatrically. Species identification based on 82 fecal DNA samples revealed that 28 and 54 fecal pellet groups were from Japanese serow and sika deer, respectively. The mean values of three fecal pellet groups characters, the maximum diameter, the proportion of adherence of fecal pellets (maximum number of adhering pellets/total pellet number), and pellet number, were significantly different between the two species. These values reflect the differences in their defecation behaviors, and piled fecal pellet groups of Japanese serow can be clearly distinguished from those of sika deer. A stepwise discriminant analysis selected only one fecal pellet group character, the proportion of adherence of fecal pellets, and provided the highest correct classification rate (82.1% for Japanese serow and 88.9% for sika deer). The proportion of adherence of fecal pellets is an important parameter for discriminating between Japanese serow and sika deer on field surveys.