How many years do rats grow? - briefly
Rats attain adult size in roughly five to six months, after which growth ceases. Their typical lifespan ranges from two to three years.
How many years do rats grow? - in detail
Rats reach physical maturity rapidly. The typical laboratory rat (Rattus norvegicus) attains adult size within 5 to 6 weeks after birth. During this period, weight increases from a few grams at birth to 300–500 grams for males and 250–350 grams for females.
Growth phases can be outlined as follows:
- Neonatal stage (0–3 days): rapid organ development, limited locomotion.
- Pre‑weaning stage (4–21 days): food intake shifts from maternal milk to solid diet; skeletal growth accelerates.
- Weaning stage (21–28 days): separation from mother; growth rate peaks.
- Post‑weaning stage (28–42 days): body reaches near‑adult dimensions; sexual maturity begins.
After the initial six‑week period, rats continue to gain mass at a slower rate until approximately 3 months of age, when growth essentially ceases. Lifespan varies with strain, environment, and care, averaging 2 to 3 years for standard laboratory strains, with some outbred varieties living up to 4 years. Wild rats typically survive shorter, often less than 1 year, due to predation and disease pressures.
In summary, rats complete their growth cycle within the first 6 weeks, achieve full size by 3 months, and may live for up to 3 years under optimal conditions.