When buying a pet gerbil, it is important to know the sex of the animal, especially if you intend to buy more than one. Accidentally buying one male and one female could result in unwanted gerbil pups. The best ways to avoid this mistake are to get your gerbil from a breeder or to learn how to sex gerbils yourself. The differences between male and female gerbils are not as obvious as they are in other animals. However, it is relatively easy to tell them apart with a little practice.
Sanitize your hands before picking up a gerbil. If handling babies, rub your fingers on the bedding before touching them to disguise your scent.
Pick up a gerbil by gripping it gently around the ribcage. Turn it over to view clearly its belly and the area beneath its tail.
Look for four nipples near the outer edges of the belly. These are areas of bare skin surrounded by whorls of fur. These mark a female gerbil.
Find the anus of the gerbil right under the tail. Look for a small, hairless, heart-shaped sac of skin. These are the testicles of a male. Not all males have hairless testicles, so you may have to use more than one method to sex your gerbil.
Look for a small, hairless bump of skin above the anus; this is the urinary opening. If it is very close to the anus, almost touching, it is a female. If it is a centimeter or more above the anus, it is a male with fur-covered testicles.