How much does a four-month-old rat weigh? - briefly
«Four‑month‑old rat» typically weighs between 250 g and 300 g, depending on strain and sex. Laboratory data place the average at approximately 275 g.
How much does a four-month-old rat weigh? - in detail
A rat that is four months old typically reaches near‑adult size. For the common laboratory strain (Rattus norvegicus), average body mass falls within the following limits:
- Males: 250 g – 350 g
- Females: 200 g – 300 g
These values assume standard laboratory conditions: ad libitum access to a balanced pelleted diet, ambient temperature of 20 °C – 22 °C, and unrestricted cage space. Variation arises from genetic background (e.g., outbred versus inbred strains), nutritional regimen, and health status.
Growth curves for laboratory rats show rapid weight gain during the first six weeks, followed by a slower increase that plateaus around the fourth month. At this stage, the skeletal system is fully developed, and body composition stabilizes, making the recorded weights reliable indicators of adult size for most research purposes.
In wild‑caught or pet populations, weight may differ due to diet quality, activity level, and environmental stressors. Typical wild adults range from 150 g to 300 g, with some individuals exceeding 350 g under abundant food conditions.
Consequently, when estimating the mass of a four‑month‑old rat, reference should be made to the specific strain, sex, and husbandry parameters to obtain an accurate figure.