WASHINGTON, D.C.- Researchers at the Smithsonian Conservation Biology Institute have discovered why older females are rarely able to reproduce—and hope to use this information to introduce vital new genes into the pool. SCBI scientists and collaborating researchers analyzed hormones, eggs and the uteri of 34 cheetahs at eight institutions, and determined that while the hormones and eggs of cheetahs older than 8 years appear normal, the animals’ uterine tracks tend to suffer from abnormal cell growth, infections and cysts that prevent pregnancy. “Those of us who work with cheetahs have anecdotally noted that it’s hard to reproduce older cheetahs, but this is the first time anyone has documented how aging affects the physiology of reproduction in this species,” said Adrienne Crosier, SCBI cheetah biologist and lead author of the study in which these results were published. “We were relieved to f