To breed responsibly, you must only ever use strong, healthy adult animals. And you may never put any male together with any female, because there is a high risk of in-breeding. For instance, if you’ve been given a brother and sister from neighbor’s litter, it’s better not to breed them. Pairing these animals together is a serious form of in-breeding, and who can guarantee that your neighbor’s litter was not also the result of pairing a brother and sister? Most rodents live in fairly isolated ground in the wild. Scientist wondered whether this life does not automatically lead to multiple in-breeding. In-breeding means that a female mates with a relative (father, brother, uncle or nephew). In-breeding is harmful, because the same genetic information appears several times in diluted form. The animals do not only appear increasingly similar, but they also develop a one-sided character. In practice, animals become smaller, less fertile and vulnerable to illness and hereditary disorders through in-breeding (or very selective breeding). Scientific research has shown that in-breeding hardly ever occurs in wild gerbil populations. Females in season leave the colony nearby. Then they return to their own group to give birth and raise the young with the help of their uncles and aunts.
When the times has come for a litter, you have to bring male and female together. This is called “pairing’. In the wild, the partners can choose each other and they have plenty of room available. This is completely different in captivity. The owner choose the partners and puts them in a relatively small space (the cage). Normally the pairing runs smoothly. It is advisable to provide plenty of shelter in the cage, so the partners can escape from each other, if necessary. You can fill the whole cage with a tick layer of fresh hay and a number of tins and toilet rolls. Always put the female into the male’s cage, and never vice versa! If the coupling is not successful this way, you can put the female into a small show cage. These cages are approximately ten by fifteen centimeters and are available in most pet shops. Put the cage (with a well fitting lid) into the male’s cage on its side, so that the animals can see and smell each other through the lid. They can even act aggressively towards one another, but they cannot injure each other. After about 24 hours, you can let the two animals together. This will normally go without problems.
A female is ready for mating when she is at certain point in her cycle. She is in season only in this one phase (the oestrus). The season occurs once in four to six days and lasts for about twelve hours. Male gerbils normally only try to mate with females when they are in season. A complex foreplay proceeds the actual covering (which normally happens in the evening). The animals chase each other around, and drum with their paws once a while. They also smell each others genitals. When the female is ready, she stands still and lifts her back end, so that the male can mount her. Gerbils mate quickly (less than half a minute), but often. The male has to penetrate the female approximately ten times before he ejaculates. He cleans his genitals after each penetrate. The female only cleans herself after the ejaculation.