What does a rat’s estrus look like? - briefly
During estrus, female rats show a swollen, reddened vulva and display lordosis reflexes in response to male contact. The fertile window lasts 12–24 hours within a 4–5‑day cycle, and vaginal smears contain mainly cornified epithelial cells.
What does a rat’s estrus look like? - in detail
Rats exhibit a brief, highly repeatable estrous phase that can be identified by a combination of physical and behavioral markers. During this interval the vaginal opening enlarges noticeably; the mucosa becomes pink‑to‑reddish, moist, and may appear slightly swollen. The external genitalia are often more prominent, and a faint, musky odor may be detected, reflecting increased secretion of pheromonal compounds.
Behaviorally, females display heightened receptivity toward males. Typical responses include a lordosis posture—arching of the back and elevation of the hindquarters—when a male approaches or mounts. The animal may also exhibit increased locomotor activity and frequent solicitation of contact. These signs usually emerge in the afternoon of the proestrus day and peak during the estrus window.
Physiological correlates support visual assessment. Serum estradiol concentrations rise sharply in the 24‑hour period preceding estrus, while luteinizing hormone surges at the onset of the receptive phase. Vaginal cytology reveals a predominance of cornified epithelial cells, which can be confirmed by a quick smear stained with methylene blue or a similar dye.
Key characteristics of the receptive period:
- Duration: 12–24 hours, often confined to the dark phase of the light cycle.
- Vaginal swelling: noticeable, pink‑tinged, and moist.
- Cytology: >80 % cornified cells in a smear.
- Hormone profile: peak estradiol, followed by LH surge.
- Behavior: lordosis, increased movement, attraction to males.
Detection protocols typically combine direct observation of the external genitalia with a brief vaginal smear. Consistent timing of observations—preferably at the same hour each day—improves accuracy in tracking the cycle, which repeats every 4–5 days in laboratory‑bred strains.