My female mice fought after cleaning. How to reintroduce them?

Thanks for reaching out about Sadie and including a photo. It appears as if the two new females where bonded and are bonded and ganging up on your first mouse. They can be aggressive but rarely do serious damage. But provide multiple hiding areas, food dishes, water dishes and area of rest. But if aggression continues, they might have to be separated. Good luck.

Generally you need to know gerbils tend to fight and are better kept separated, it's just too common to end up with a severely injured gerbil when kept together. if you do decide to introduce them after all, put them in 2 different cages next to each other first for 2 weeks, then try to put them together under your supervision only.

There is a good chance that 2 adult male hamsters will fight and induce significant injuries. If you would like to try to introduce them to each other regardless, I would start with a completely clean cage with fresh bedding and keep them on either side of a mesh divider so that they can see and smell each other without being able to fight. I do not recommend putting one into the other’s cage as the original hamster will likely become extremely territorial. For 2 weeks or so, you can remove the mesh divider for short periods of time while you are carefully monitoring them and offering plenty of enrichment in the form of shelters, toys, food treats to keep them occupied. If you notice any aggression, I would give up and keep them separate from then on. If after several supervised periods alone (about 30 min each time) over 2 week you do not notice any signs of aggression, you may remove the mesh divider but examine them carefully each day for scabs/wounds especially on the rumps, genital area, hind legs. Good luck! They are very cute!

Usually siblings raised together will be able to live together. It sounds as if you have one overly dominant female though. You can try keeping them in a larger cage with additional bowls, bottles, toys and hides. This may give them enough "elbow room" which may decrease the squabbling. If not, you may need to separate them for a few days. A gradual reintroduction can be tried, but if they continue to fight, permanent separation may be the only option.

I'm so sorry to hear about Kahlua. When one of a pair dies, it can be hard on the surviving rat. Slow, quiet introductions are best. Letting them smell each other through the cage at first is a good idea, then short, supervised visits outside the cage. If they seem to be getting along, you can increased their visit time, then move on to allowing them to visit inside the cage you intend on letting them live in together. I wouldn't leave them alone together in their cage until you're confident that they aren't fighting aggressively. This is unusual for female rats, but it can happen. Play fighting is one thing, but if one continuously chases the other, you may need to keep them separated for their safety. I hope that this isn't the case, and that you end up with a new set of best friends! My condolences for the loss of Kahlua, and best wishes for Oreo and her new buddy.

You could start by feeding them on each side of the door that separates them so they can smell each other and have it be a positive experience. Next, you can switch rooms - lock your cat in her room so your cat can investigate the smell of her cat and let her cat roam the house. Then you can try them together while you can supervise and see what happens. You could get some Feliway spray or a diffuser and use that to alleviate any stress/anxiety.

Unfortunately yes, it can be very common for hamsters that are housed together to start fighting. This can occur even if the hamsters have always been together. I would recommend keeping them separated for a couple days and then trying to re-introduce them again like you did last night. Hopefully they will be able to get along with each other in the long run. If not, to keep them safe, you'll have to keep them separated. I hope this helps. Thanks for using Petco Pet Education Center, formerly Petcoach. Best of luck.