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Hamsters sometimes become aggressive, without any immediately obvious cause. However, there is nearly always a good reason for the behavior. It may simply be that the hamster has not been hand-tamed. This is a simple and important process. A new hamster will not have any familiarity with the human hand, and will act defensively – i.e. aggressively – as a result.
To find out how to tame your hamster, see the Holding a Hamster page of this guide.
Even if your hamster has been tamed, problem behaviors may still arise. These are triggered by illness or fear. Knowing a little hamster psychology will help you work out what the underlying issue us.
Hamsters may bite if they are stressed, afraid, or ill
Why Do Hamsters Bite?
If your hamster bites you when you hold it, there are several potential reasons:
- Your hamster has not been tamed
If your hamster has only just been brought home, or has never been hand-tamed, it’s probably biting because it’s frightened of you. When you put your hand in the hamster cage, the animal will instinctively think the hand is a predator.
- You are not holding your hamster properly
If you grab your hamster suddenly, it may bite out of fear. Move your hand towards your pet slowly, and then he won't be scared. Hamsters may also nibble you if you’re not holding them correctly. See the Holding a Hamster page for a guide to hand-taming.
- You have woken your hamster too early
Hamsters are active in the late evening and at night, and will become disorientated and stressed if you wake them during the day. If they are confused and scared, they are likely to bite. Always play with your hamster during its natural waking hours in the evening, night or early morning.
- Your hamster is mistaking you for food
Hamsters’ eyesight is very poor, and will usually nibble first and ask questions later! So, if you often stick food through the cage bars, and then do the same with your finger, the hamster will not immediately spot the difference.
- Your hamster is unwell
Some medical conditions, such as mange or a wound, make a hamster very sensitive. Being handled will be painful for them in these circumstances. If your hamster suddenly objects to being handled, when formerly he was quite happy with it, it could be indicative of a health issue. Examine your hamster visually, or handle it wearing protective gloves if a visual check doesn’t reveal what the problem is.
Circling or 'Twirling'
A hamster that runs in circles continually is possibly be suffering an ear infection, or a brain injury. Take your pet to the vet for a diagnosis and treatment.
Fighting
If your hamsters fight, you’ll need to separate them, perhaps even permanently. If the fights are frequent, or if one aggressive hamster is preventing another from accessing food, you will have to intervene.
Syrian hamsters should never be kept in the same cage in the first place, after the age of six weeks when they mature. They are very territorial, and their fights can be fatal. Dwarf varieties sometimes turn on each other for no apparent reason, although it is often to do with not having enough space. If they fight, you will need a second cage in order to keep them apart.
Hamsters may fight, even species that can usually live together happily
Remove the hamster that is being aggressive and keep it in the separate enclosure for a few days. If the animals still fight when reunited, they will have to be permanently separated.
Sometimes hamster fighting is just an occasional bickering. If no blood is drawn, and if the flare-up appears to have died down, keep a close eye on your hamsters to make sure the fall-out is over. You can often stop these squabbles by having separate food bowls and water bottles for each hamster.
Severe scratching
The occasional 100-mile-an-hour back-leg scratching is normal. But if your hamster is continually scratching, even drawing blood in the process, he could have a health problem such as mites or mange. Give your pet a thorough health-check to try to determine the cause.
If you have started using a new type of bedding recently, this may possibly be the cause. Switch back to the old bedding for a while and see if the scratching persists. If the cause of the problem doesn’t become obvious, take your pet to the vet for a diagnosis.
Bethany, 15 April 2021
I have just brought a Syrian hamster and I have never owned one before. I have not yet tamed her as she bites me whenever I try and I’m in the process of getting her a larger cage. Her current cage has a tunnel attached and she will sleep in there all day. The thing that concerns me is the fact that whenever she now goes into the tunnel, she will run back out as if running away from something. She also keeps scratching at herself. I think she may have mites but I cannot hold her to check myself. What should I do?