Female animals regularly enter a phase where they are sexually active and receptive to males; this is collectively known as the [[Female Reproductive Tract -Oestrous Cycle - Anatomy & Physiology|oestrous cycle]]. Some animals are able to reproduce all year round, but many have an anoestrus phase which requires a [[Female Reproductive Tract -Seasonality of Reproduction - Anatomy & Physiology|seasonal response]] for cycling to begin. | Female animals regularly enter a phase where they are sexually active and receptive to males; this is collectively known as the [[Female Reproductive Tract -Oestrous Cycle - Anatomy & Physiology|oestrous cycle]]. Some animals are able to reproduce all year round, but many have an anoestrus phase which requires a [[Female Reproductive Tract -Seasonality of Reproduction - Anatomy & Physiology|seasonal response]] for cycling to begin. |