Reproductive season of Japanese squirrels (Sciurus lis) in the northern part of Chiba Prefecture

Abstract

During a 12-year survey, I directly observed eight cases of reproductive events of Japanese squirrels (Sciurus lis): one case of mating bouts, one case of copulation, two cases of carrying young, three cases of lactation, and one case of maternal behavior out of the nest at three sites in the northern part of Chiba Prefecture (35°N, 139–140°E, elevation 10–30 m). The results suggest that the species reproduces twice a year in the study area. Reproductive schedules are estimated as follows; the first breeding season: copulation in January–March, birth in February–April, independence of young in May–July; and the second breeding season: copulation in late June, birth in August, independence of young in October. Compared with the previous studies carried out at Takao, Tokyo (35°N, 139°E, 170–265 m) and at Tateshina plateau, Nagano Prefecture (36°N, 138°E, 1,500–1,600 m), we confirm that the Japanese squirrel reproduces twice a year in lowlands and hills of the Kanto region and mountainous areas of the Chubu region.