Reproduction of female Sika deer (Cervus nippon yesoensis Heude, 1884) in Ashoro District, Hokkaido.

The authors studied some reproductive characteristics of wild female sika deer (Cervus nippon yesoensis Heude, 1884) in Ashoro District, Hokkaido. Large numbers of females attained sexual maturation at the age of yearling, and the pregnancy rate of yearlings and older was 96.4% (n = 28). These high levels of fertility should be considered the standard for high quality populations of sika deer. The estrus cycle began in late October. Twinning was exceptional. Sex ratio of fetuses was statistically 1:1, and there was no significant difference in fetal weights between males and females in March. The birth weight is estimated to be around 6 kg. Accessory corpora lutea were found in 77.8% (n = 27) of pregnant females.