Merck Manual

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Rats at a Glance

Rats at a Glance

Life span

1.5 to 3 years

Length

Body: 9 to 11 in (23 to 28 cm)

Tail: 7 to 9 in (18 to 23 cm)

Weight

12 to 23 ounces (350 to 650 g)

Cage temperature range

64°F to 79°F (18°C to 26°C)

Relative humidity

30% to 70%

Breeding age

6 to 12 weeks

Estrous cycle

4 to 5 days

Gestation period

21 to 23 days

Litter size

8 to 18 young

Weaning age

21 days