Finding if a guinea pig is a female or a male (also called sexing the guinea pigs) is quite easy and it can be done regardless of the age of the guinea pig. You need to carefully pick up the guinea pig and examine its genital area. If you notice a puckered looking spot just above the genital area, it's a good possibility that you're holding a male, but you need to be positive.
Next, press gently just above the genital area. If the guinea pig is a male, his *** should come out. If the guinea pig is young, you can also examine the area around the animal's rectum. A donut-shape also signifies a male because this is where the guinea pig's testicles are located.
While sexing a guinea pig may not sound pleasant and may sound like a downright invasion of the animal's privacy, you should always check instead of relying on the advice of a pet shop worker. Many, many families have been told by the sweet and friendly young people selling these creatures at the local pet store that their new guinea pigs are the same sex only to find out two months later that they've just been blessed with grand pigs (or great grand pigs, depending on who takes care of the animals).
If you don't feel comfortable with the process, do yourself and your family a favor and either don't buy a guinea pig from a pet store or only buy one guinea pig. If you go to a reputable and experienced guinea pig breeder, he or she will be able to tell you with confidence what gender your new guinea pig is.
Ok, now as promised, there are a few differences between male and female guinea pigs that may prompt you to choose one gender over another, although for the most part the positives and negatives basically balance out.
Male guinea pigs are usually somewhat larger than the females, but the difference is not overwhelming. More importantly, the males tend to be much more active than the females, and it may take them longer to calm down with children.
Female guinea pigs, on the other hand, are normally much calmer than the males and are sometimes easier for children to handle. However, if you purchase a female from a pet store or an unreliable breeder, you may end up bringing home more than you bargained for since she could already be pregnant. Overall though, both male and female guinea pigs make excellent additions to almost any family.
Florian Ross is a freelancer and small animals expert. For more tips on raising Guinea Pigs and having them live 3 times longer, see http://www.pets-lovers.com/guinea-pigs/guinea-pigs.htm