Last month I unfortunately had to separate my gerbils Astra and Twiglet. They had been having on-and-off issues for about a year. I had previously been able to resolve each episode of tension by temporarily reducing their space and enrichment. However, every time they would be fine for a few months, and then it would flare up again. And every time the tension flared up, it would be worse than the last time and occur with less warning. One day last month they had a couple of physical scuffles. When gerbils declan, it usually happens as a process with multiple stages, and physical scuffles are the second-to-last stage before actual bloodshed. So the only safe option was to separate them permanently.
I believe the root cause of the declan was a simple disagreement over dominance. Every gerbil pair/group has a dominant gerbil, usually the biggest one. Twiglet is a very large gerbil with a meek personality. Astra is a very small gerbil with a bossy personality. Due to her size, Twiglet ended up dominant by default, but as they got older, Astra became dissatisfied with this and that's what caused the episodes of tension. In the beginning, I thought it might be related to them maturing, and thought that if I could get them through the tricky young adult months, Astra would settle down and accept her position as the subordinate gerbil. But she was evidently very determined. So although the gerbils had some good times together, I think they're fundamentally incompatible.
However, every cloud has a silver lining. After I separated Astra and Twiglet, I reserved two young pups at a local rescue, so that I could introduce one pup to each of them. I collected them on Saturday and put them in split tanks with Astra and Twiglet. While I was at the rescue, I also collected two brothers of my pups, to introduce to somebody else's lone male gerbil (Otis).
Here are the boy pups playing on a wheel:
(I actually call those little plastic wheels "baby wheels", because I only ever use them for baby gerbils!)
I set up three split tanks with the adults on one side of each, and the pups on the other.
This was Twiglet's first meeting with her pup:
As you can see, there was a little bit of possible aggression, which is common during these first meetings. They can be quite shocked and frightened when they first see another gerbil. The divider allows gerbils to get used to each other without getting hurt. In the past people often used to introduce adults and pups directly without a divider and it sometimes resulted in terrible injuries to the pup, so I always use a split tank, even if only for a few hours.
I swapped the gerbils round (so that the adult is now on the side the pup was on before, and vice versa) on Saturday evening, and then three times on Sunday. The purpose of this is to get them used to each other's scent, and to assess their behaviour. There shouldn't be too much scent marking or agitated behaviour, and they should ideally be sleeping in each other's nests. When introducing two adults, you have to do this swapping for at least a week or two so that the scents are well-distributed on both sides, but adult to pup introductions can be much shorter since it's mostly just about making sure the adult isn't going to be aggressive.
This morning I removed the dividers from each split tank (spaced about 30 minutes apart).
Here is Astra being introduced to her pup:
I didn't film the other intros, but they went well too. With Otis and the two boys, during my first attempted introduction he was really nervous about something, and the pups were picking up on atmosphere and being very jumpy, which only made him more nervous. So I put the divider back in, gave Otis some cardboard to chew, and waited an hour until he had calmed down. Then I tried again, and it went much better.
So I have two happy pairs and one trio (which will be going home to their owner in a few days).
Here is Astra giving her pup a very thorough groom, to make sure she smells just like her:
Here is Twiglet building a nest while her pup doesn't really help:
Here is Otis with one of his pups. The other one is underneath him somewhere.
I haven't named the pups yet. I've been too busy with the introductions to think about it much. But hopefully I'll think of something soon.