How to Determine the Sex of a Rat

If you have more than one pet rat you will need to be careful to determine the sex of your rat before you decide whether or not to house them together. Rats breed very quickly and if you are not careful your two rats will quickly become 50 rats. Luckily, it's pretty easy to determine the sex of your rat so you can avoid any accidents.

Difficulty: Easy

Instructions

1. Hold your rat gently yet firmly in your hands and turn it over so that it's belly is facing you.

2. Look at the belly and genital area. A male rat will have large testicles and a female rat will have nipples. Be aware that male rats will draw in their testicles when they get scared, so they may be hard to find.

3. Determine the sex of a rat as young as 10 days of age. Females will have small dots where the nipples will be and males will have a small bump where the testicles and penis will be located.

4. Observe a rat's behavior. This will also help you to determine their sex though this is not a fool-proof method. Male rats tend to be quieter and more affectionate than female rats, although males may go through an aggressive stage when they enter adolescence at around six months of age.

Tips & Warnings

• Rats don't have breeding seasons, but extremely hot or cold weather will decrease the frequency of mating.
• Female rats go into heat about every three to four days all year long. Going into heat usually begins in the evening and ends in the morning.
• Female rats enter menopause at around 18 months of age.
• Rats breed very quickly. Don't keep male and female rats together unless you want to have lots of babies. Male and female rats will need to be separated at five to six weeks of age.
• Female rats do not have periods. If you notice vaginal bleeding take her to the vet immediately.