GROWTH, DEVELOPMENT AND REPRODUCTION IN CAPTIVE OF THE LARGE JAPANESEFIELD-MOUSE, APODEMUS-SPECIOSUS (RODENTIA, MURIDAE)

The large Japanese field mice (Apodemus speciosus) were captured and k ept in stainless cages under a constant condition at 23 degrees C and 14 L: 10 D photoperiod, and the growth, development and reproduction w ere investigated in this species. Modification of feeding condition an d nest materials and introduction of a chamber and a running wheel app aratus into each cage first enabled this species to breed under captiv ity. In our breeding colony, A. speciosus produced the pups throughout tile year. Concerning sexual maturation of the males, the descended t estes and spermiogenesis were observed at 50 days old, copulatory beha vior was performed at about 60 days old, and active breeding started a t 70-80 days old. On the other hand, in the females, the vaginas opene d 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), rang ing 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 fi eld 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.