Even contact between different pets of a similar size can be a major mistake. Gerbils tend to be extremely aggressive towards other small rodents. They will normally attack and attempt to kill hamsters, rats and mice. Before gerbils are about 8 weeks they will normally except the company of other Gerbils. Unfortunately, after that age it gets more difficult to introduce them.
Males are much more easy to introduce to one another.
They will normally accept a Gerbil that is under 8 weeks old and be very protective towards it. Females on the other hand can be very difficult to introduce other Gerbils to. This is because females are much more competitive and territorial than males are. Introducing adult gerbils often requires that special steps are taken. This means that the gerbils have to live in the same tank or cage with a barrier between them.