Wondering how you can determine your rat's gender? Gender-checking aka rat sexing is important for several reasons. The most obvious reason is to prevent lots and lots of new babies running around if the guys are not separated from the girls in time. Rats can start breeding from as young as 5 weeks old, so identifying their genders is key to making sure that you don't accidentally have girls and boys together. Another reason to keep genders apart is that there is a much bigger chance of fighting. That's the last thing you want to deal with – especially when you've just experienced the joy of seeing those babies being born and watched them start to develop.
So, when's the best time to sex rats? As a general guideline, it's best to find the golden time between not hurting them when they're just a few days old and not waiting too long until they're sexually mature. We share some advice on the best time below. What else should you know about how to tell a rat's gender? In this guide, we share some simple ways to spot the difference (don't worry – it's not as hard as you'd think). This will make it much easier to know who is female and who is male. You'll then have a chance to prepare for your new rat babies knowing that they are safely separated when it's time to leave mom.
Ready to find out more? Here are our tips on determining rat gender.
Even though boy and girl rats are just as cute and cuddly as the other, it’s super important to know what sex you own, or what sex you’re planning to own... we can't keep different sexes in the same cage. They’ll likely end up fighting. And you’ll probably soon have a bunch of new kittens (baby rats) on your hands. So how do you tell… is your rat a guy or a gal?
At only two hours old, it’s possible to tell the sex of your kittens; there’s a larger lump where the penis is on the male. However, unless there’s an immediate urgency for you to know what their sex is (I know rat parents… I know it’s hard), I’d recommend waiting until they’re 2ish weeks old. Handling too soon and too much right after birth can be stressful to them.
The key to determination of sex is the distance between the anus and urethra. Lift those little kittens out of their cage and place them on their backs in the palm of your hand. Hint: it’s easier to hold two at a time, if possible, so you can see a side by side comparison of the distance. Find the anus (under their tail) and urethra (small opening a little further up towards their stomach). The distance between these two body parts will be about 1.5 - 2 times longer in boy rats than in girl rats.
At about 9-10 days old, too, you can start to see the hint of the testicles shape appearing on your male rat, but the testes do not fully descend until about 5 weeks old, the age of sexual maturation. Note, though, that it’s possible for the testicles to retract upward into a male rat’s abdomen, so this isn’t always a surefire way to know the difference between a boy and a girl.
Oh, and girl rats have nipples. 6 on each side of her body. You’ll also be able to tell this at about 9 days old (on darker colored rats; light colored rats are more difficult to spot). That's another little hint.
So if you want to know if your rat’s a guy or a gal, follow these steps. It’s exciting to learn the sex of your rat. Plus, then you’ll be able to figure out a cute, appropriate name.
