How long do domestic rats grow? - briefly
Domestic rats typically reach full length of 9–12 inches (including tail) and a weight of 300–500 g within about five to six months of age. After this period growth slows dramatically, and they remain at adult size for the rest of their lives.
How long do domestic rats grow? - in detail
Domestic rats typically reach their full body length between 6 and 12 months of age. The measurement includes head and body, excluding the tail, which adds an additional 20–30 cm. Adult females average 18–20 cm, while males are slightly larger, ranging from 20–25 cm.
Growth proceeds through distinct phases:
- Neonatal (0–3 weeks): Birth weight 5–7 g; rapid weight gain of 2–3 g per day.
- Weaning (3–5 weeks): Transition to solid food; body length increases to about 8–10 cm.
- Juvenile (5–12 weeks): Steady growth; weight reaches 150–250 g; length approaches 15 cm.
- Adolescent (12–24 weeks): Growth rate slows; males may add up to 50 g; final size achieved by 6 months.
Factors influencing final size include genetics, diet quality, and health status. Selective breeding for dwarf or miniature strains can produce adults as small as 10 cm in body length, whereas standard pet rats often exceed 20 cm. Adequate protein (18–20 % of diet) and consistent feeding schedules promote optimal development. Illness or chronic stress can stunt growth, leading to reduced length and weight.
Weight correlates with length: an adult male typically weighs 300–500 g, while females average 250–350 g. Tail length, though not part of body measurement, mirrors overall size; longer-tailed individuals often belong to larger breeds.
In summary, a pet rat’s mature length falls within a 18–25 cm range, achieved by the end of its first half‑year, with variations dictated by sex, strain, nutrition, and health.