Horn Growth and Reproductive History in Female Japanese Serow

Abstract

To elucidate the relationship between horn growth and reproduction, we measured the annual horn growth increments and histologically examined the ovaries of 132 female Japanese serow ( Capricornis crispus ). The number of small growth increments observed in each horn coincided with the number of elastoid bodies, thought to be the retrograde corpora lutea of pregnancy, in the ovaries of 77.6% of females ≥4.5 years old. Therefore, horn growth measurements can be used to trace the reproductive history of females. Horn growth measurements were used to estimate age-specific and annual fertility rates in a sample of 172 females from a wild population. Age-specific fertility rate peaked at 6 years of age (81.0%). Fertility rate of females ≥3 years old averaged 71.5% for 1981–83. Age when first reproduction occurred ranged from 2 to 5 years. Annual probability of reproducing was greatest for the female group that reproduced first at 3 years old.