The Sexual Cycle of the Thirteen-Lined Ground Squirrel in the Laboratory

The almost complete lack of reproduction by the several hundred ground squirrels, Citellus tridecemlineatus, in our laboratory led to experiments to promote such reproduction (Johnson and Wade, 1931). Anterior pituitary implants, ultra-violet light, a diet rich in vitamin E, and ovarian extracts and implants did not increase reproduction. During this study it became evident that the sexual development of different individuals varied greatly, and that very little was known of the sexual cycle in captivity.