When does a rat grow up? - briefly
Rats reach sexual maturity at roughly five to six weeks of age. Full adult size is attained by eight to twelve weeks.
When does a rat grow up? - in detail
Rats reach physiological maturity within a relatively short lifespan. After a gestation period of 21–23 days, newborns weigh 5–7 g and are hairless, with eyes closed.
During the first week, pups double their birth weight and begin to develop fur. By day 10, the eyes open and sensory responses become coordinated.
Weaning occurs around day 21, when solid food replaces maternal milk. At this point, body weight typically reaches 30–45 g, and the skeletal system has progressed to near‑adult proportions.
Sexual competence emerges shortly after weaning:
- Males produce sperm and exhibit mounting behavior by 5–6 weeks of age.
- Females enter estrus cycles and can conceive by 6–8 weeks.
Physical growth continues until approximately 12 weeks, when rats attain full adult size (250–300 g for common laboratory strains) and display stable adult behavior patterns. After this stage, further changes are limited to age‑related physiological decline.