"estrous cycle." YourDictionary, n.d. Web. 18 December 2018. <https://www.yourdictionary.com/estrous-cycle>.
estrous cycle. (n.d.). Retrieved December 18th, 2018, from https://www.yourdictionary.com/estrous-cycle
The series of changes that occur in the female of most mammals from one period of estrus to another. The estrous cycle usually takes place during the period known as the breeding season, which ensures that young are born at a time when the chance of survival is greatest. The length of the cycle varies from species to species.