How can I determine the sex of a one‑month‑old rat? - briefly
Examine the region under the tail: males have a noticeably longer anogenital distance and visible scrotal bulges, whereas females show a shorter distance without testicular swelling. Gentle palpation to feel for testes provides definitive confirmation of a male.
How can I determine the sex of a one‑month‑old rat? - in detail
Inspect the animal with gentle restraint, using a bright light source to illuminate the ventral side. Position the rat on its back or hold it upright while supporting the tail with a thumb and forefinger. Examine the area between the anus and the genital opening.
- Males display a pair of testicles located in a shallow scrotal sac just posterior to the penis. In a one‑month‑old specimen, the testes are small, may appear as two rounded, pinkish masses, and can be felt as slightly raised bulges. The penile opening (prepuce) is a narrow slit situated ventrally and slightly anterior to the anus.
- Females lack visible testes. Instead, a single, smooth, round opening (the vulvar slit) is present, positioned directly beneath the anus. The labial folds are minimal and do not form distinct bulges. The distance between the anus and the genital opening (anogenital distance) is shorter in females than in males.
If visual identification is difficult, gently palpate the region with a gloved fingertip. A firm, movable mass indicates male gonads; a soft, uniform tissue suggests a female. Use a magnifying lens if necessary to enhance detail.
Key considerations:
- Perform the examination in a calm environment to reduce stress.
- Keep the rat’s body temperature stable; cold can cause the testes to retract further, obscuring their outline.
- Avoid excessive force; delicate handling prevents injury and yields clearer observation.
- Record findings with photographs when permissible, ensuring consistent lighting and angle for future reference.
By systematically evaluating external genital morphology, testicular presence, and anogenital distance, the sex of a juvenile rat can be reliably determined.