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The rumen contents of sika deer (Cervus nippon Temminck) on the Boso Peninsula, central Japan, were analyzed to identify local, sexual and age-specific differences in food habits. Graminoids and woody plants were the primary foods throughout the year. In winter, the use of evergreen broad leaves increased. The food habits of sika deer on Boso Peninsula were intermediate between those of populations inhabiting northern and southern Japan. Acorns, mainlyLithocarpus edulis Nakai, were consumed in fall and winter with a peak in October. Since the availability of acorns is not influenced by foraging in previous years, it can be regarded as a stable food supply and hence may be important for deer on the Boso Peninsula. The local difference between the Amatsukominato (AT) area, having a large plantation ofLithocarpus producing acrons, and the Kamogawa-Katsuura (KK) area, having a small plantation ofLithocarpus, was recognized; seeds and fruit were consumed more in AT than in KK in fall and winter. Males consumed more seeds and fruit than females at both sites in fall. This can be attributed to sexual differences in nutritional requirement.

The size-sex relationship and sexual differences of sixArisaema species native to Japan were investigated. The size-sex relationship showed almost the same pattern in all species. When the plant was small in size, the sex expression was male, and sex expression changed from male to female as the plant grew larger. Male ratios decreased rapidly around a critical size, but this critical size differed from one species to another.

The mark-and-recapture method was used to study the lifetime movement of the Japanese skimmer,Orthetrum japonicum, in a forest-paddy field complex in the warmtemperate zone of Japan. The flight season was from mid April to late June. The age structure showed that the maiden flight occurred towards the forest from the emergence sites (paddy fields) for both sexes. The insects returned to the paddy fields after maturation. The total number of skimmers estimated in the whole survey area was about 1000–2000, of which about 200 males were found in the paddy fields. The average lengths of the immature and reproductive periods were about 10 and 20 days in both sexes, respectively. Most mature males tended to stay in the paddy fields and showed territorial behavior, while most mature females moved frequently between the forest and the paddy fields. The average extent of each territory was about 19 m2, being established mainly in the shady paddy fields. Few males were sneakers. The available habitat throughout the life span for the skimmers was both the paddy fields and the forest.