How much does a rat weigh? - briefly
A typical adult laboratory «rat» weighs between 250 g and 500 g, varying with strain and sex. Wild brown «rat» specimens usually average around 300 g.
How much does a rat weigh? - in detail
Rats display considerable variation in body mass depending on species, age, sex, and husbandry conditions. Laboratory strains such as the Sprague‑Dawley and Wistar typically reach a mature weight of 250–350 g for females and 300–500 g for males. In contrast, the smaller Norway rat (Rattus norvegicus) found in the wild often weighs between 150 g and 300 g, with juveniles under 50 g. Exotic species, for example the fancy dwarf rat (Rattus rattus domestica), may remain below 100 g throughout adulthood.
Key factors influencing mass:
- Genetic line: selective breeding produces distinct size categories.
- Nutritional regime: high‑calorie diets accelerate growth and increase adipose tissue.
- Environmental temperature: colder conditions stimulate higher body fat deposition.
- Health status: disease or parasitic load can cause weight loss.
Measurement practices in research settings employ calibrated electronic balances with a precision of 0.01 g. Animals are typically weighed after a brief acclimation period to reduce stress‑induced fluctuations. For field studies, portable spring scales or trap‑mounted platforms provide estimates, though accuracy may be limited to ±5 g.
Conversion to other units: 1 g ≈ 0.001 kg ≈ 0.035 oz. Thus, a typical adult laboratory male weighing 400 g corresponds to 0.4 kg or about 14 oz.
Understanding the weight range assists in dosing calculations, cage space allocation, and welfare monitoring. Regular weight tracking, expressed as a percentage of expected growth curves for the specific strain, enables early detection of abnormal health conditions.