How to determine the sex of domestic rats? - briefly
Examine the anogenital area: males display a noticeable scrotum and a larger, rounded opening, whereas females have a single, slit‑like opening without a scrotum. By 3–4 weeks of age these characteristics are reliably distinguishable.
How to determine the sex of domestic rats? - in detail
Identifying the gender of pet rats requires careful observation of external genitalia, which become distinguishable after the first week of life. The primary structures to examine are the anogenital distance, the presence of a scrotum, and the development of nipples.
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Anogenital distance (AGD): Measure the space between the anus and the genital opening. In males, this gap is roughly twice that of females. A ruler or fine caliper can provide a quick estimate, but visual comparison is usually sufficient.
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Male indicators:
- A visible scrotal sac located just behind the anus.
- Two small, rounded openings (preputial pores) on either side of the scrotum.
- Slightly larger AGD.
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Female indicators:
- Absence of a scrotum; the area behind the anus appears smooth.
- A single, round genital opening (vulva) directly in line with the anus.
- Shorter AGD.
For newborns (P0‑P3), the genital papilla is not yet fully formed, making sex determination more challenging. In these cases, gently lift the tail and examine the ventral side with a magnifying glass. The presence of a tiny, hair‑covered ridge indicates a male; a smooth surface suggests a female. Patience and gentle handling reduce stress and improve accuracy.
Common errors include confusing the anal glands with the scrotum and misreading the ventral fur pattern. To avoid these mistakes, clean the area with a warm, damp cloth before inspection, and compare the specimen with a known‑sex reference if possible.
When uncertainty persists, a veterinary professional can confirm gender through a brief physical exam or, if needed, ultrasound imaging. Accurate sexing is essential for proper breeding management, health monitoring, and social grouping of domestic rats.