Growth, Development and Reproduction in captive of the Large Japanese Field Mouse, Apodemus speciosus (Rodentia, Muridae)

The large Japanese field mice (Apodemus speciosus) were captured and kept in stainless cages under a constant condition at 23°C and 14 L: 100 photoperiod, and the growth, development and reproduction were investigated in this species. Modification of feeding condition and nest materials and introduction of a chamber and a running wheel apparatus into each cage first enabled this species to breed under captivity. In our breeding colony, A. speciosus produced the pups throughout the year. Concerning sexual maturation of the males, the descended testes and spermiogenesis were observed at 50 days old, copulatory behavior was performed at about 60 days old, and active breeding started at 70-80 days old. On the other hand, in the females, the vaginas opened and mature follicle cells appeared at 60-70 days old at which active breeding began in females. The mean litter size was 4.29 (n=27), ranging from 3-6, and the gestation period was 19-21 days in this species. Significant sexual difference were detected in each increase in body weight, head and body length, tail length, foot length and ear length. These growth rate constants were similar to each other among the four compared species that belong to genus Apodemus; the Korean striped field mouse, A. agrarius chejuensis, the small Japanese field mouse, A. argenteus, the Formosan wood mouse, A. semotus and the large Japanese field mouse, A. speciosus.