Reproductive cycle of female Chinese green tree vipers, Trimeresurus stejnegeri stejnegeri, in northern Taiwan

From March 1996-August 1997, we studied the reproductive cycle of 132 femal e Chinese green tree vipers, Trimeresurus stejnegert stejnegeri, in norther n Taiwan by examining seasonal changes in their hormone levels and reproduc tive organ morphology and histology. Based on follicle size and the presenc e or absence of corpora lutea, we classified each female into one of five r eproductive cycle stages. Ovulation occurred in stage IV while stage V was the post-partum stage. Liver mass peaked during stages II and III when vite llogenin is demanded for vitellogenesis. Changes in kidney mass and fat bod y mass paralleled changes in liver mass. Most histological characters of th e oviduct, including epithelium height and gland diameter, increased gradua lly during stages I through III, and declined thereafter. Serum progesteron e concentration peaked in stage IV while serum estradiol peaked in stage II I. Stage I females were considered non-reproductive while females in stages II to V were classified as reproductive. The ratio of reproductive to non reproductive females was nearly 1:1. However, the proportion of reproductiv e females increased significantly with female body size. These results sugg est that female Chinese green tree vipers have the potential to breed annua lly but often reproduce less than once per year. Like crotaline snakes from temperate areas, female Chinese green tree vipers in northern Taiwan exhib ited low-frequency reproduction, postnuptial vitellogenesis, and long-term sperm storage.