" Although female grizzlies mate during the spring, embryo development and pregnancy are suspended for a few months in a process called delayed implantation. This means if it’s not a good year for food and the female is unable to gain enough weight to successfully produce cubs, the embryo will be reabsorbed and the pregnancy won’t proceed. "

― Carolyn Jourdan , Dangerous Beauty: Encounters with Grizzlies and Bison in Yellowstone