How do rats of different ages look? - briefly
Newborn pups are hairless, pink, and weigh only a few grams; juveniles develop a soft gray‑brown coat and open eyes. Adult rats have dense brown or black fur, larger bodies, and more pronounced snouts and ears.
How do rats of different ages look? - in detail
Rats undergo distinct physical changes as they progress from birth to old age. These transformations are observable in size, fur development, sensory organ maturity, and skeletal growth.
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Newborn (0–10 days)
- Body length: 3–5 cm, weight 2–5 g.
- Skin: thin, translucent, almost hairless; visible blood vessels.
- Eyes: closed, eyelids fused.
- Ears: small, folded against the head.
- Tail: proportionally short, covered with sparse, fine hairs.
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Infant (10 days–3 weeks)
- Fur: begins to emerge, initially sparse and light-colored.
- Eyes: open around day 13, iris pale gray.
- Ears: start to unfold, gaining mobility.
- Teeth: incisor buds visible, but not yet functional.
- Weight: 10–15 g; length increases to 7–9 cm.
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Juvenile (3 weeks–8 weeks)
- Fur: fully developed, denser, typical coat coloration (e.g., brown, black, albino).
- Body: rapid growth; length 12–15 cm, weight 30–60 g.
- Tail: length matches body, covered with uniform hair.
- Teeth: incisors fully erupted, continuously growing.
- Musculature: noticeable increase in limb strength and coordination.
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Adult (8 weeks–12 months)
- Size: body length 15–20 cm, weight 200–500 g depending on strain.
- Coat: mature coloration, may show subtle pattern variations.
- Tail: long, slender, proportionally 1.5–2 times body length, covered with fine hair.
- Skeletal: fully ossified vertebrae and long bones.
- Reproductive organs: visible development in males (testes descend) and females (vaginal opening evident).
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Senior (12 months and older)
- Body: may exhibit slight reduction in muscle mass, increased fat deposits.
- Fur: may become thinner, grayer, or develop patches of alopecia.
- Tail: skin may lose elasticity, occasional loss of hair in sections.
- Eyes: lens may appear cloudy, indicating cataract formation.
- Teeth: wear patterns become pronounced, occasional overgrowth if not gnawed.
These stages provide a reliable framework for identifying a rat’s age class based on observable physical attributes.