You can only introduce adult gerbils safely through the split-cage method. You can introduce a single gerbil to another single gerbil but you cannot introduce a lone gerbil to an existing group - it will be killed. The main exception to this is two male pups recently weaned to a single adult male.

Introductions

Male just weaned pups to an adult male: This is the easiest way to introduce gerbils and may not need any split-caging. If the adult male is a year or older it is best to get two pups so that the gerbil pup is not left lonely in the future. It may be safer to have the splitcage up for a short period to check that the male is accepting of the babies.

Please note that any gerbil old enough to be on the shop floor of a petshop, is too old to use this method. The pups ideally need to be about 5 weeks old, although as long as they are under 8 weeks they should be fine.

Male to Male: Moderate difficulty. Expect at least a week of split-caging.

Female to Female: Very difficult. Split-cage for several weeks and ensure that the females are both the same size.

Male to Female: Moderate, and should only be attempted if you have thoroughly research the ethics and genetics of breeding, as well as ensured that there is a strong pet market for gerbils in your area. You should not breed from animals that you do not know the genetic history of, and please be sure to vet any potential homes carefully and do not sell to petshops as otherwise you could end up supplying a meal for a reptile. For more details, see our article on When to breed rodents - Ethics and Care.

Building the split cage

Once a secure gerbil split-cage is constructed then fill with your substrate of choice, such as megazorb, some bedding. Attach a water bottle to each side. Do not add any toys or anything they can scent mark. This means any cardboard you give them must be thin and quickly demolished. You should also avoid food bowls, scatter feeding is more interesting for gerbils anyway as gerbils are natural foragers.

Place a gerbil on either side of the double-layered mesh. They may well scratch and bite at the mesh and attempt to get at the other gerbil. This is normal. Several times a day swop the gerbils over so they are on different sides. Never change any part of the bedding or substrate so that the scent of both gerbils is on both sides. You cannot handle the gerbils other than when you are swopping them over, or in the event that you are checking their health.

Do this for at minimum of a week, depending on your combination. After a week if the signs are positive, remove a layer of mesh to allow the gerbils a little more access.

Positive signs include:

• Sleeping flank to flank against the mesh.
• Grooming each other through the mesh.
• Sleeping in the bed used by the other gerbil.

Removing the divider

When you have seen positive signs from the gerbils, you may be ready to remove the divider. Do this slowly and have some heavy gardening gloves to hand in case you need to separate them. You will need to put aside a day to observe the gerbils once the divider is removed and do not introduce any new items to their cage at this time. You need to keep them in the tank with the old bedding and substrate as this is where all their smells are.

You may witness your gerbils boxing - this is where they stand on hind legs and jump or batt at each other with their front paws. This is fine, and is just a way of establishing dominance. Chasing, squeaking and squabbles are also fine.

You MUST intervene if one gerbil persistently chases the other without stopping to do anything else, such as dig, eat or chew. If any blood is drawn you also need to separate. The most dangerous sign is where your two gerbils curl into a ball together - this means they are trying to kill the other gerbil and you must separate. If this occurs, replace the barrier and leave for another week until positive signs emerge again. If two or more attempts are made and this keeps happening, the gerbils may never accept each other.

If things are positive and you have monitored the gerbils carefully then it may be safe to keep the divider removed overnight. DO NOT do so if there are any concerns. Consider moving them into a bedroom so that you would be awakened by sudden movements or sounds and be able to intervene. Do not add anything new to their tank.

If signs continue to be positive you can add new things very gradually over the course of the next few weeks. Remember not to separate your gerbils for any long period of time, even for vet visits and if you handle one try to make sure you do so with the other to ensure your scent is on both. Be wary of any sudden new smells, such as painting your room and continue to keep an eye out for any dangerous signs. By this stage chances are very high, you've helped out your lonely gerbil!