Abstract
By using preserved testes and epididymis obtained from ten dead individual captive male giraffes (Giraffa camelopardalis reticulata and G. c. tippelskirchi) raised in the zoological gardens in Japan, an evaluation of the age of sexual maturity was attempted. Histological observation using HE and PAS-hematoxylin stainings revealed the existence of spermatozoa in the testes and epididymis in giraffes older than 5.9 years of age. Immunolocalization of P450scc in the testes appeared in the individuals at 2.5 years of age and 5.9 years of age and older. The estimation of the age at the first successful copulation was also attempted by reviewing the studbook in the Japanese zoological gardens between 1907 through 2000 and this revealed the most frequent age to be between three to five years. These results are coincident with the results obtained by histological observation. The lowering of the breeding age was observed in the captive giraffes. It was speculated that the lowering of the breeding age in the captive giraffe may be caused by the absence of older male giraffes which usually obstruct copulation by the younger males in the wild.
