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Behavioural traits in rodents and what they may mean.

Ball fighting is where two rodents curl into a ball and this is where a fight has escalated and does need to be separated. Gerbils in particular must be separated if this happens.

Some rodents rise on their hind legs and bat at each other with their front paws. This can be play-fighting and fairly minor, but if one animal does not back down or lose inter­est this can escalate.

Brux­ing is where an animal grinds or chat­ters its teeth together quite rapidly. This can indi­cate con­tent­ment, espe­cially when occom­pa­nied with bog­gling. How­ever brux­ing can also occur as a reac­tion to pain or stress — if the sound is louder, and with more sharp cracks, it is more likely to be the animal respond­ing to some­thing bad. Rodents may brux loud (some­times known as chat­ter­ing) to com­fort them­selves if they are in dis­tress or pain.

Rats are particularly known for this.

As a prey species, rodents have a strong survival instinct and so when a companion dies they may well eat the body to dispose of it - and thus leave no traces for a predator to help locate them.

Some rodents may cannibalism their young if the nest is disturbed too early, or they are distressed for other reasons. Sometimes this can indicate a lack of protein in their diet.

Sometimes rodents that have lived together for a long time can have seri­ous fights and decide they can no longer live together. This is known as declan­ning. Female gerbils are known for this in later life, if kept in numbers greater than a pair. If declan­ning occurs in a pair then you may be able to reunite using the split-​cage method, but you can­not intro­duce a sin­gle ger­bil to an exist­ing pair or clan.

If blood hasn’t been drawn then one of the most com­mon prob­lems may be odour, say if you han­dled one rodent with­out han­dling the other or if there is as strong smell in the room such as if you have recently painted. A dust bath is a good start to try and neu­tralise this for some species.

Sometimes this isn't declanning, but where a species has been sold to an owner without the proviso that they may not have a good chance at staying together for life. Dwarf hamsters from pet shops for instance, can be difficult as they will be hybrids - and so may have inherited different percentages of traits and not be compatible with each other.

A certain amount of dominance play will be how your group establishes its hierarchy. Although this is often spoken of as needing an Alpha - this is not a concrete rule. 

Dominance behaviour includes pinning - where an animal will hold another in a position where their belly is upwards. They might then groom or sniff them, or just do nothing. This is normal.

Grooming is a dominance behaviour and it may seem sometimes as if this is being forced. This is particularly common where an animal has been kept incorrectly without companions, one result is that the lonely animal may groom quite excessively when finally introduced to company. This should only become a concern if the grooming becomes excessive to the extent that other animals fur is becoming patchy, or fights are breaking out because of the over enthusiastic one.

Groom­ing is a something rodents do to themselves, and to each other. Sometimes this is a bonding behaviour but it can also be dominance, especially whilst establishing hierarchy. See dominance behaviour for more details.

Rodent may groom themselves whilst nervous, using teeth and claws. It can look like they are nibbling at their fur. Rodents do this to keep themselves clean, although some species may also require a dust bath to prevent fur from becoming too greasy.


Head Swaying is something a pink or red eyed animal may do to compensate for some distortion in their vision.


Rodents moult their fur from pup to adult where a baby coat is replaced with a smoother adult version. Some changes also occur as adults, Nutmeg gerbils for example, have quite dramatic colour changes and the lines of this can sometimes be seen quite clearly along their fur.

Winter White Hamsters will change coat colour as the light changes in winter, as a natural camouflage against the snow.



This can sometimes be a form of dominance behaviour, or an indication that one animal is in heat. This is mostly harmless although worth keeping an eye on if one animal is persistent in case it leads to more serious behaviour.

If this is observed with new animals, it is always worth double and triple checking genders in case an error has been made!

Some rodents will use their scent glands to mark their ter­ri­tory. It is often a high-​ranking or alpha that will do this most, and they may also secrete small droplets of urine as a form of mark­ing. This does not indi­cate incon­ti­nence and not all rodents will do this.

Cleaning out rodents too often may lead to excessive scent marking. Not only will this actually lead to a greater overall smell, but more importantly this puts a greater strain on their kidneys.

Stereotypical behaviour is a behaviour a rodent exhibit typically when coming from an overcrowded home or where kept without important aspects.

Rodents such as gerbils for instance will develop compulsive burrowing in the corner of a cage if brought up without a burrow. If mum is given an artificial burrow - an enclosed chamber with tunnel attached - then these pups will grow up without this behaviour.

Another stereotypical behaviour is bar chewing, and this is something that can be improved by ensuring the rodent has enough space and toys to alleviate the boredom. Some rodents may keep exhibiting this behaviour regardless.

Excessive wheel running is another troublesome behaviour, and this can be tackled by offering the wheel in limited time slots or even removing completely. It's important to monitor the weight of any rodent that develops an obsession with their wheel!

Some rodents rattle or thump their tail. This can be used to express aggression, annoyance or sometimes is a sexual behaviour.

Information on introduction methods, quarantine, split-caging and others.

Bin cages are plastic tubes - often using an RUB as a base - with meshed sides to allow ventilation. These are used as cheap and custom accomodation for rodent keepers.

Do you have a good method, or guide for making these? We'd love someone to write an article on making your own bin cage!

Some animals can be introduced together on neutral territory - this is important to ensure that no existing scents are carried across. It is important to monitor and not offer any existing toys or things to hide in until you are confident they are getting on.

See information on introducing on neutral territory

Some rodents, such as mongolian gerbils, can only be introduced using the split-cage method.

You may want to quar­an­tine new animals before intro­duc­ing, for a period of a few days or weeks.This is especially important if they have come from a pet shop.

This will only be effec­tive if you have a place to keep them that does not share the same air­space as your cur­rent animals. You will also need to be very care­ful about wash­ing your hands and the equip­ment used whilst doing this.

Signs of ill­ness include: Poor coat con­di­tion, posture, sud­den weight loss, squeaky, laboured or oth­er­wise noisy breathing. Lethar­gic and cool to the touch, lack of inter­est in food or water, diar­rhoea or constipation, exces­sive scratching.

Split-caging is the process of introducing some territorial rodents to each other in a gradual way to reduce chances of injury and to enable them to get accustomed to each other. Some rodents can only be introduced via this method.

See information on split-caging.

Health and medical issues. This section is intended as a guideline and does not substitute for veterinary advice.

Abscesses can be caused by fights and are generally softer than cancerous lumps. They can be drained by your vet.

Excess scratch­ing, sneez­ing, runny or swollen eyes are signs that your pet may have an allergy. It is worth switch­ing their bed­ding and sub­strate to see if this can solve the prob­lem, although if you see no improve­ment after a few days then it will require a vet visit.

Barbering can be caused by rodents overgrooming or chewing the fur or whiskers from another rodent. This can be caused by stresses such as overcrowding, poor diet or dominance issues. Excessive barbering may require separation of the animals.

Cataracts in rodents can be spotted initially be seen as a white dot behind pupil and the lens may develop a gray or milk white discoloration. They are more likely to occur in older animals.

A vet should be consulted and some adaption of cage layout to account for poorer vision may be needed.

Cushings Disease is a disease known in Syrian Hamsters. Signs of Cushings Disease include hair and weight loss, loose and flaky skin, increased thirst, dark pigment patches on the skin and cuts, scabs and wounds to the skin.

For more information on Cushings Disease see the Hamster Central Wiki entry.

Deglov­ing is where the fur, skin, and mus­cle have been torn off an animal’s tail, leav­ing mus­cle and bone exposed. This is an extremely painful injury and will need vet treat­ment includ­ing pain relief. The miss­ing part of the tail may never grow back but could poten­tially be amputated.

Some species can be prone to this and care must be taken with their diet. Hybrid hamsters are especially likely to develop this, as are Campbells Russian Dwarf Hamsters and Chinese Hamsters. Signs of dia­betes in ham­sters include excess thirst and fre­quent urination. Diabetes can be controlled with medication.

It is impor­tant to ensure your animals are kept well hydrated so check their water bot­tles and bowls. A com­mon cause of diar­rhoea in mice is too many green veg­eta­bles in their diet.

Mild cases of diar­rhoea can be treated by sprin­kling Arrow­root pow­der over their nor­mal food. Arrow­root can be obtained from most herbal food shops or your local super­mar­ket.

Diarrhoea can be very serious in young or vulnerable animals and a vet should be consulted.

Animals with red or pink eyes have poorer vision than those with black. They may sway their head from side to side, as they have more difficulty focusing. As rodents rely more on smell, than sight, this does not affect their quality of life.

See also glaucoma and porphyrin (red tears).


Glaucoma in rodents in currently not treatable, although your vet can prescribe eye drops. Issues with visions may require care taken with cage layouts, to avoid sudden drops or changes. Winter White Hamsters are known for developing Glaucoma.

A persistent head tilt needs to be investigated by your vet, this could be a sign of an ear infection or something more serious.

This is different to Head Swaying, which is something a pink or red eyed animal may do to compensate for some distortion in their vision.

A build up of fluid on the brain. Asian Garden Dormice can be prone to this, potentially due to inbreeding in the UK given bloodlines are not tracked.

Mycoplasma pulmonis is the most common cause of respiratory infections in rats and mice who are three months or older.

Neutering can be done on male animals in order to enable them to live with the opposite sex without risk of babies. This does require an experienced vet and time will be needed after the operation before the animal is safe to be introduced to the opposite sex.

Female animals can be spayed, with can reduce the risk of developing some cancers.

Male mice can be neutered, which allows them to then live with female mice which can be a good solution to an otherwise solitary existence since male mice are very difficult to keep together with their own gender without fighting.

Parvoviruses attack rapidly dividing cells and are species specific, for example the Rat Parvovirus (RV) is also known as Kilham rat virus and under natural conditions will only affect rats.


The red colouring in gerbils tears are caused by an organic compound known as porphyrin. These causes the 'red tears' that can look like blood.

This can be caused by allergies to substrates - a common cause is using sawdust, a substrate which is not suitable for rodents.

A prolapsed penis (paraphimosis) can occur in even the smallest of rodents and should be referred to a vet if it persists.

Any animal that has issues with breathing, either due to speed or noise, should see a vet. A rodent that makes an audible noise, like a snuffling or clicking sound, may have a respiratory infection.

Mycoplasma pul­mo­nis is the most com­mon cause of res­pi­ra­tory infec­tions in rats and mice who are three months or older.


Ringworm is a skin lesion that can result in fur loss, although some rodents can display no symptoms. Some variants can be communicable to humans.

This is usually treated with topical antibiotic/steroid creams or antifungal medications.

Excessive scratching or grooming can led to serious skin problems. This can be caused by Mites, and the affected animal may display anything from mild scratching to severe, with patchy hair and skin ulcerations. Beaphar spot-on can be a good treatment, bearing in mind adjustment must be made for the weight of your mouse. More serious causes of mites may require your vet to prescribe something such as Ivermectin.

Another cause of habitual scratching could be boredom, see our section on enrichment and general care for ideas of how to keep your mice happy. You may also want to consider changing your substrate as some animals can have allergies to a specific type.

Seizures are a very upsetting thing to watch and it is best to adapt your cage layout to ensure your rodents safety if this is something they are prone to. They can have a variety of causes, including epilepsy, and a vet should be consulted.

Young gerbils may experience seizures that they grow out of.

Sendai Virus (SV) is also called parainfluenza is a common type of respiratory infection, which can affect mice, rats and hamsters. See also Respiratory Infections.


Rodent's teeth are con­stantly grow­ing so you must pro­vide mate­r­ial to help wear it down. Occa­sion­ally an animal with a jaw­bone or teeth abnor­mal­ity such as Malocclusion may need reg­u­lar trips to a vet to trim their teeth.

Dental Caries, or tooth decay, can occur in rodents and can occur where an animal is fed too many sweet or honeyed treats.


Lumps are sadly quite common in some animals, especially with female mice. They can be caused by a variety of issues, such as an abscess (often caused by fighting), polyp, prolapse or a cancerous tumour.

Some research suggests that mammary tumours have a very high possibility of recurrence as there is a chemical in the lumps that prevent others occurring.

Scent gland tumours in gerbils can be removed by an experienced vet.

Abscesses are generally softer than cancerous lumps and can be drained by your vet. An animal with a lump may still have many months of life left, depending on its location and does not need to be put to sleep until it begins showing signs of pain or unhappiness.

This is a highly con­ta­gious and often fatal dis­ease. It can occur in ham­sters with­out devel­op­ing any symp­toms, although oth­ers will show lethargy, ill-​kept coat and diar­rhoea. Tyzzer’s Dis­ease is caused by stress and unclean envi­ron­ments so can be mostly pre­vented with good hygiene practices.

Wet Tail is a form of watery diar­rhoea that is extremely seri­ous in ham­sters, if left untreated your ham­ster will die of dehy­dra­tion. Wet tail can be caused by poor or stress­ful con­di­tions, and is sadly quite com­mon in ham­sters bought from pet shops or uneth­i­cal breeders. Wet tail is mostly seen in Syr­ian Ham­sters. Any ham­ster with sus­pected

Wet tail must be iso­lated as it can be highly con­ta­gious. Imme­di­ate vet treat­ment is needed.

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