Sexing baby rats

Sexing rats is fairly easy with a few guidelines. First, check the rat yourself–pet shop employees nearly always make mistakes. By the time the baby rats are weaned (4 – 5 weeks of age) the males’ testicles will have dropped, but they aren’t always obvious because they can be voluntarily pulled inside the body. You should be able to see the scrotum, though, which will take up much more room between the anus and genitals than in the females. The best thing to do is to compare several rats until you find two that look different. Then it should be obvious which is the male and which the female

llustration compliments of Deb “ratlady” Ducommun

Remember that the distance between the female’s anus and Urethra is generally shorter than the same in the Male because the Male’s testicles need the space to form there.

Rattie Life cycle

Age in days Age in weeks/months  Development stages
Birth  Hairless, toothless, closed eyes and ears relies on smell of mother/siblings
4 days 4 Days Hair begins to appear
10 days 1.5 weeks Covered with hair
13 days Almost 2 weeks  Eyes and ears open
40-50 days 5 weeks to 7 weeks  Weaned at 5 to 6 weeks

Sexual maturity

72 days 2.5 months  Young adult
 250-300 days 8 – 10 months Young adult
 1000-1300 days 32 – 42 months (2.7 to 3.5 years) end of normal lifespan Full grown; males larger than females


Rats are very intelligent.  Proof of this is that they are used by many researchers to test problem solving abilities.   The classic example of this would be the lab rat in the maze.

Researchers have found that rats can solve puzzles by using methods that the tester had never anticipated.

Pet rats can learn their names and recognize their human companions.  It has been said that rats have the approximate mental age of a 3 – 4 year old human.


Beware of  items around your household (especially potted plants) if your rattie has free range of your house.  See our HAZARD list for a list of poisonous plants and other dngerous edibles.