Abstract
Knowing demographic parameters is important in order tounderstand the life history of mammals. As an example, the twinning rate of sika deer, Cervus nippon, on Mt. Goyo was determined based on 2,064 samples collected from 1981 to 1997. The sex ratio of single fetuses (n=1,946) was even (49.8% males and 50.2% females). Six pairs (0.29%) of twins were found. One pair was composed of male and female embryos, suggesting that at least some conceptions are dizygotic. It was concluded that twinning is rare in sika deer. This rate was similar to, or lower than, that found in red deer, C. elaphus.
