Help! Suddenly Aggressive Hamster!

[EIS]

My hamster is suddenly acting vicious towards her sister in the past few days.

I have two female Russian Dwarf hamsters from the same litter both living together in a large cage with multiple levels. Their names are Arki and Raptor. They are 11 months old and have never been apart.

Until recently, they have been relatively peaceful towards one another and often slept together. Occasionally they wrestled in a playful manner but nothing vicious or threatening. They often chased each other and slept together afterwards. Arki would usually initiate these playful spurts and was considerably more active than Raptor. However, since cleaning the cage and replacing the substrate with sand Raptor has been active significantly more whereas Arki has become more reclusive. It seems that almost every time Raptor sees Arki, Raptor chases and attacks. Arki is wary of Raptor and spends a lot of time hiding. Luckily due to the cages size there is space for them to be alone. Weirdly, Raptor reacts to being handled the same as before with complete tameness but excluding this Raptor is almost like a different hamster.

Possibly related, Raptor is consuming more water, sometimes standing by the water bottle for up to 10 minutes drinking intermittently.

Please give me some advice, I'd hate to have to split them up.

Thanks

Images are of the cage and the hammies coexisting peacefully.

[SabreRose]

Unfortunately pairs of dwarfs can fall out as they mature. It might be safer for them to split them up. Fights can turn fatal very quickly.

[cypher]

Have you tested Raptor for diabetes? That would be my first thought with both excessive water consumption & aggressive behaviour.
Just in case you don't know you need to put her in a clean plastic box until she pees then test the urine with the same sticks used for humans that you can buy in any chemist.
If this behaviour continues regardless of whether she is diabetic (or possibly has a UTI) I think it would be best to split them up as it must be very stressful for Arki & possibly for Raptor too which in itself could lead to more health problems & possibly injuries. Fights can escalate very quickly once they begin so you need to have another cage ready to put one of them in before any serious injury occurs.

[Crystalroborovski]

It sounds as though one of your hamsters is becoming a bully to the other. The exact same thing happened with my pair of robos as they matured into adults. One would chase around and wrestle the other who became terrified to be around his brother. Once I separated the two they were both much happier- the bully was happy he didn't have to share a cage and keep dominance over his brother and the one who was being bullied became much more playful and he didn't have to worry about being attacked out of the blue by his cagemate. It is a bit of a tough decision to make but if your hamsters are fighting you are potentially saving one or both hamsters' lives. I would suggest separation- Arki is probably very stressed and Raptor probably is too.

I'd like to point out a few things-
Sand is not a good substrate to use for the whole cage, mainly because it does not hold burrows. Whilst it is beneficial for keeping your hamster's fur clean and their nails trim, it should only be used in a small section of the cage, perhaps in a shallow bowl so that it can be cleaned up easier. It would be a good idea to take out a lot of the sand and only leave some in a section of the cage and replace the removed sand with burrowable substrate such as a paper based bedding.

I see you have platforms in your cage- these are a no with pairs. One hamster may claim a platform as its territory and attack the other one if they get on the platform. This can cause a pair to fall out.

With pairs all hideouts must have multiple exits or else one hamster could easily corner the other while they're both inside. I did have a coconut hideout in my hamsters' cage before they started falling out. I thought the exit was large enough for one to escape but after I witnessed a bad squabble inside the hideout I had to remove it from the cage for both hamsters' safety.

In the end squabbling can quickly turn to fighting, which can unfortunately be fatal for one or both hamsters. My hamsters' fighting was mild at first- only a squabble here and there. However, without me knowing, the fights escalated very quickly. It only took one week for the fighting to become so severe and the one who was being picked on was lucky he did not suffer from any bite wounds, however he did have a small scratch but it healed up quickly. Had I not woken up at 3:00 in the morning to the squealing of Tangerine (the one who was being bullied) I doubt he would have gotten away with no severe injuries. In the end it is your decision but consider the happiness of both hamsters. Good luck!

Edit- as Cypher mentioned the hamster that is constantly drinking could quite possibly have diabetes. Excessive drinking is a symptom of it. You can follow her advice on testing for diabetes.

[cypher]

I didn't actually stop & look at the photos yesterday but even though it's not relevant to your question I have to agree that the sand is totally unsuitable as a substrate, Russians really do need a sand bath or sand area but they do also need a good depth of normal substrate to dig & burrow in.
Levels aren't normally recommended for pairs but as yours have lived together for quite some time I doubt that's an issue here right now.

[CMB]

It would be best o split them up. The one standing by the water bottle is possibly guarding the water supply. This could make the other become dehydrated due to not being allowed to drink.

They will both be ok living on their own. They will take a little while to adjust though.