What is Estras Cycle? Posted in General Zoology Estras is the cyclic period of sexual activity in non human female mammals, characterized by congestion of and secretion by the uterine mucosa. During estrus the animal is said to be ‘in heat’. Share this:EmailFacebookGoogleReddit Related posts: What is Cell-Cycle? 50 CPMT Entrance Zoology Qeustions and Answers 2008 Function of Integument Plasmodium life cycle phases "Interphase is a resting phase"