Vol. 36 No. 1, 1997

Annual Reproductive Cycle of the Formosan Wood Mouse, Apodemus semotus

Bu-Miin Huang*, Liang-Kong Lin and Paul S. Alexander

Dept. of Biology, Tunghai Uriiv., Taichung, Taiwan 407

Bu-Miin Huang, Liang-Kong Lin and Paul S. Alexander (1997) The annual reproductive pattern of Apodemus semotus was studied. A. semotus specimens were trapped at monthly intervals from October 1984 through  March 1986 at about 2300 m elevation in the Hohuanshan area of central Taiwan (24˚ latitude). Reproductive parameters of 267 mice were measured. Seasonal changes in weights of male gonads showed peaks in April-May and September-October, whereas gonadal weights were sharply reduced and there was histological evidence of regression in June-July and December-February. Ovarian monthly mean weights also showed 2 peaks in April and September. Pregnant or lactating  females were found in April-May and August-December. Breeding was more frequent in autumn than in spring. The mean litter size of 23 pregnant mice was 3.83 ± 0.88 (range 2-6). The difference between litter size and ovulation rate (4.24 ± 0.22) indicates that prenatal mortality was 12.8%, including 7.5% pre-implantation mortality and  5.3%  post-implantation mortality. No more than 2 sets of placental scars were found in any individual. Analyses of age structure and the time of appearance of juveniles give further evidence of a bimodal annual  reproductive pattern tor A.semotus.

Key words: Rodent, Reproduction,Bimodal, Gonad, Apodemus.

*Correspondence: Current address: Dept. of Anatomy, College of Medicine, National Cheng Kung Univ., Tainan, Taiwan 701, R.O.C. Tel: 886-6-2353535-5337, Fax: 886-6-2353660, E-mail: bumiin@mail.ncku.edu.tw