How can you determine a rat's sex? - briefly
Inspect the ventral area: males display a prominent scrotum and a longer anogenital distance, whereas females have no scrotum and a shorter distance between the anus and the genital papilla.
How can you determine a rat's sex? - in detail
Identifying a rat’s gender requires careful examination of external anatomy, which differs between males and females once the animal reaches sexual maturity (approximately 5–6 weeks old). The following steps provide a systematic approach:
- Position the rat: Gently restrain the animal on a soft surface, supporting the hindquarters with one hand while the other hand lifts the tail to expose the ventral area. Avoid excessive force to prevent stress or injury.
- Locate the anogenital distance: In males, the space between the anus and the genital papilla is noticeably larger than in females. Measure roughly 5–7 mm in mature males versus 2–3 mm in females.
- Examine the genital papilla: Male rats possess a prominent, rounded papilla that protrudes forward. Female rats lack this structure; instead, a small, recessed opening (the vaginal orifice) is visible.
- Observe the presence of testes: In adult males, a pair of oval, firm testes lie within the scrotal sac beneath the tail. In younger males, the testes may be undescended and appear as small, firm masses near the abdomen. Females have no comparable structures.
- Check for nipples: While both sexes have nipples, the pattern is more pronounced in females, especially during pregnancy or lactation. However, nipple appearance alone is insufficient for definitive sexing.
- Confirm with secondary characteristics: Mature males often exhibit a larger body size, broader head, and more pronounced scent-marking behavior. Females may display a slightly smaller stature and a more rounded abdomen when pregnant.
If uncertainty remains, especially in juvenile rats where sexual dimorphism is subtle, a short-term observation of behavior (mounting, territorial marking) can provide additional clues. In research or breeding settings, genetic testing or histological examination of gonadal tissue offers definitive confirmation, though such methods are typically reserved for specialized circumstances.