Wild gerbils are highly territorial desert dwellers that bear their young in hidden underground nests. Your domestic gerbils are primed to procreate as if their prodigy also had to endure the hardships of desert life. They can reproduce early and often and will do so readily if not secured in same sex cages after they reach two months of age. Don't risk gerbil babies you can't afford to take care of. Make sure you can find a home for every pup before you proceed with breeding your gerbils.
The most difficult part of breeding your gerbil is introducing him to a compatible mate. Because gerbils are territorial, your pet may resist the advances of any "stranger" gerbil and even fight the intruder to the death. A gerbil often accepts his sister as a mate, but inbreeding has its own negatives. As generations of gerbils are bred with their close relatives, the likelihood that negative or deleterious genes will be expressed in the offspring is greatly increased. This can mean unsightly mutations like baldness or kinky tails, or even invisible problems with the digestive tract and other vital systems that may prove fatal.
To trick your gerbil into accepting a strange mate, try dusting him with talcum powder, being especially careful to dust the scent glands on his abdomen while avoiding his eyes, ears and mouth. You can also use a cheap non-toxic perfume to disguise your pet's natural scent. Dust your pet's intended partner as well and place the pair in a cage that is foreign to both of them.
Since neither of the animals will recognize the spot as their own territory, they may be more willing to accept one another. Be sure to keep a pair of gloves on hand to separate the two if they fight. If after two introduction attempts there has been no peace, you will have to find a different mate for your pet.
Gerbils are polyestrous, which means they are sexually responsive or "in heat" several times a year. They can mate and rear offspring regardless of the season. To signal to a female gerbil that he is ready to mate, a male gerbil approaches her and thumps the ground with his back legs. If she is receptive to his advances, the female gerbil will back her hindquarters up to the male so that he can mount her. A gerbil's gestation period is approximately 25 days.
You may not be able to discern that your female gerbil is pregnant by looking at her, but you will observe an increase in the pair's nesting activity right before the litter is born. In the wild, gerbils line their nests with seed husks and other plant fibers, but you can give them tissue paper, toilet paper rolls or fabric to work with. Never give them cotton wool, which has fibers that are too small for the gerbils to manage and may be unintentionally ingested. A 10-gallon aquarium tank should be large enough for one pair of gerbils to build a nest for their new litter.
Gerbils have between one and 12 babies each litter, with an average litter of between five and eight pups. The pups are the size of a peanut in its shell and are born with closed eyes, no teeth and no hair. Try not to touch the babies during the first week because their mother will be highly sensitive to your scent. If you must touch them, rub a little of the bedding on your fingers before you pick up the pups to disguise your scent.
It is perfectly safe to keep the male gerbil in the cage with his pups, though he will not likely be much help for the female gerbil. Be aware that your female gerbil can be impregnated just one day after giving birth to her litter. You can give her a few extra sunflower seeds and fresh vegetables to boost her fats and calcium intake while she nurses the pups. The babies will have hair by day 10 and will open their eyes two weeks after being born. From this point on, almost all of their energy will be devoted to squirreling out of the nest, while all of their mother's energy will be concentrated on keeping them in.
The pups can be weaned at 21 days and you should remove them from their parent's cage if you intend to breed the original pair again. Female gerbils have a reproductive life of around 15 months and can be expected to raise an average of seven litters during this time if allowed to mate freely. Male gerbils are sexually active for slightly longer, though your gerbils will likely live for more than a year after they stop actively breeding.