If a fertile post-partum mating does occur, a delayed implantation usually ensues, particularly if the female is nursing a large litter. Delayed implantation may lengthen the period of gestation up to 42 days. Breeding Gerbils are usually monogamous and if a mature gerbil loses its mate for any reason, it may not accept another. The male gerbil aids in caring for its young. Isosexual pairs also form strong bonds.
Gerbils breed readily in the laboratory environment.
Litters will average four to six young with a range of from one to 10. If paired gerbils are separated to avoid post-partum mating, they must not be kept apart for more than two weeks or fighting may occur when they are reunited. Weanling gerbils may be sexed at any time after birth on the basis of ano-genital papilla distance, which is approximately double in the male to that in the female. Handling and Specimen Collection Gerbils can be handled quite freely and there is usually no danger and very little difficulty in handling pregnant females either with young litters or even newborn pups. In picking the animal up, the base of the tail should be grasped and the body supported in the other hand.