How much does an adult rat weigh? - briefly
A mature rat generally weighs between 250 g and 500 g, with laboratory strains averaging around 300–350 g. Variation depends on species, sex, and diet.
How much does an adult rat weigh? - in detail
Adult rats typically weigh between 250 g and 500 g (approximately 9–18 oz). The exact mass depends on species, sex, environment, and nutrition.
- Species: The common brown rat (Rattus norvegicus) averages 300–500 g, while the black rat (Rattus rattus) is slightly lighter, usually 180–300 g.
- Sex differences: Males are generally 10–20 % heavier than females of the same species.
- Captive vs. wild: Laboratory specimens, fed a controlled diet, often reach the upper end of the range (450–500 g). Wild individuals, subject to variable food availability and predation risk, commonly fall between 250 g and 350 g.
- Age: Rats achieve full adult size around 10 weeks; weight stabilizes thereafter, with minor fluctuations linked to reproductive cycles in females.
Factors influencing body mass include:
- Dietary composition: High‑protein, calorically dense feed promotes greater weight gain.
- Health status: Parasite load or disease can reduce body condition.
- Housing conditions: Overcrowding may limit individual growth, while spacious enclosures allow normal development.
Weight measurement is performed with calibrated digital balances, recording to the nearest gram. Researchers often convert grams to ounces (1 oz ≈ 28.35 g) for comparative reporting.