How does estrus look in rats? - briefly
During estrus, a female rat’s vulva becomes markedly swollen and pink, often accompanied by a clear to whitish vaginal discharge. She also shows heightened sexual receptivity, exhibiting lordosis when a male is present.
How does estrus look in rats? - in detail
Estrus in female rats is marked by distinct external and internal changes that can be observed without invasive procedures.
Externally, the vaginal orifice enlarges noticeably; the opening may appear rounded and more prominent than during diestrus. The surrounding skin often takes on a pinkish hue due to increased blood flow, and a clear to milky vaginal discharge becomes evident. The discharge is typically viscous, may contain a small amount of blood, and can be detected by gently pressing the area with a cotton swab.
Behaviorally, rats in estrus display heightened receptivity to male stimuli. They approach or remain near a male, assume a lordosis posture when presented with a mounting attempt, and emit ultrasonic vocalizations in the 50‑kHz range. These vocalizations increase in frequency and intensity during the fertile window.
Internally, the uterine horns swell and become engorged with fluid, reflecting preparation for potential implantation. The cervix softens, and the epithelial lining of the vagina exhibits a proliferative state, characterized by increased cellular height and mitotic activity. Hormone assays reveal a peak in estradiol concentrations approximately 24‑48 hours before ovulation, followed by a rapid rise in luteinizing hormone (LH) that triggers ovulation.
Timing is consistent across strains: estrus lasts 12‑14 hours, typically occurring in the late afternoon of the proestrus day. Monitoring the cycle by daily vaginal cytology—identifying predominance of cornified epithelial cells—confirms the onset and duration of the fertile phase.
In summary, estrus in rats presents as an enlarged, pinkish vaginal opening with characteristic discharge, increased sexual receptivity, and measurable hormonal fluctuations, all occurring within a predictable 12‑hour window.